Ben Creisler's Plesiosaur Pronunciation Guide
Copyright © Ben Creisler 2000-2012
The proper English translations of generic names and related taxon, and their preferred pronunciations.
(Moved to Oceans of Kansas, July 7, 2012)
Alzadasaurus Welles 1943 "Alzada (
(Alzada + Gr. sauros "lizard") (m) named for the town of
Aphrosaurus Welles 1943 "sea-foam lizard"
AF-ro-SAWR-uhs (Gr. aphros "sea foam" + Gr. sauros "lizard")* (m) named to indicate a marine reptile; known from incomplete skeletons without skulls of an adult and a small juvenile, found in the coastal Moreno Formation, in Fresno County, California. A rather lightly built elasmosaurid with relatively short coracoids, described as a "less active but longer-necked form than Morenosaurus" (Welles 1943).
Vertebrae: 57 cervicals
Length: (estimated) ?10 m. (?33 ft.))
Type Species: Aphrosaurus furlongi [FUHR-long-ie] Welles 1943: for Eustace L. Furlong of the California Institute of Technology. (Holotype: CIT 2748). Plesiosauroidea Elasmosauridae Late Cretaceous (Maastrichtian) NA.
Apractocleidus Smellie 1915 "functionless clavicle"*
a-PRAK-to-KLIE-duhs (Gr. apraktos "functionless, incomplete" + Gr. kleid- (kleis) "key, clavicle" + -us) (m) named for the rigidity of the shoulder girdle, which rendered the clavicles "functionless." [= Cryptoclidus]
Aptychodon Reuss 1855 "unwrinkled tooth"
(Gr. aptykhos "unwrinkled" + Gr. odon
"tooth") (m) named for the smooth appearance of the teeth; based on a
number of eroded teeth found near
Archaeonectrus Novozhilov 1964 "ancient swimmer"
AHR-kee-o-NEK-truhs (Gr. arkhaios "ancient" + Gr. nektris "swimmer" + -us) (m) named to indicate a plesiosaur found in Early Jurassic deposits; proposed for "Plesiosaurus" rostratus Owen 1865, known from a complete skeleton with skull from the Lower Lias of Carmouth, England (Holotype: BMNH 38525). Notable for a relatively short neck (about 1.5 times the length of the skull) composed of short cervical vertebrae, and a large elongated head with a narrow snout and round orbits. The teeth are pointed, conical and recurved. The hindlimbs are larger than the forelimbs. Owen (1865) notes that some of the centra of the tail vertebrae were vertically compressed, suggesting to him the possible presence of a vertical tail fin. Novozhilov (1964) mentions undescribed remains from the Early Jurassic of Siberia that appear to belong to the genus.
Vertebrae: 20 cervicals / 4 pectorals / 23 dorsals / ?3 sacrals / 34
Length: (estimated) 3.5 m. (12.5 ft.); skull: 50 cm. (20 in.))
Type Species: Archaeonectrus rostratus [ros-TRAY-tus] (Owen 1865) "rostrate" ("having a rostrum"), for the elongated rostrum formed by its snout. Pliosauroidea Early Jurassic (Sinemurian) Eur.
Aristonectes Cabrera 1941 "best swimmer"
(Gr. aristos "superior, best" + Gr. nektes
"swimmer") (m) named to indicate the best specimen of a plesiosaur
found up to that time in Argentina--the first Argentine plesiosaur based on
absolutely secure scientific evidence. Previous "plesiosaur"
The classification of Aristonectes remains controversial. Cabrera placed the genus among the elasmosaurids, based mainly on the single-headed ribs on the vertebrae (a feature common to many Cretaceous plesiosaurs). Persson (1963) classified Aristonectes along with Cimoliasaurus and Scanisaurus in the Cimoliasauridae, a poorly known group characterized by medium-length necks and rather long skulls with thin teeth. (See Cimoliasauridae.) Welles (1962) proposed that the genus was "an aberrant pliosaur." Brown (1981) included the genus in the family Cryptoclididae because of its dense arrangement of teeth, a feature in common with the Late Jurassic Cryptoclidus. Bardet (1995), however, considers Aristonectes and the apparently related but smaller Morturneria to be elasmosaurids, in line with Cabrera's original thinking.
Vertebrae: 30+ cervicals
Length: (estimated) ?7.5-8 m. (?25-27 ft.); skull: (estimated) 73 cm. (2.3 ft.); mandible: (estimated) 83 cm. (2.6 ft.)
Type Species: Aristonectes parvidens [PAHR-vi-denz] Cabrera 1941 "small-toothed," for the small size of the teeth, indicated by the size of the aveoli. The tooth sockets decrease in size from 8.5 mm in diameter in the front of the jaws to 6 mm at the back and show the teeth protruded at an angle. Though no actual teeth were found with the remains, it is likely the teeth were thin, pointed, and slightly recurved, forming a dense "trap" for schools or swarms of small prey. (Holotype: Museo de La Plata, Departamento de Paleozoologia, Vertebrados 40-XI-14-6). Plesiosauroidea ?Cryptoclididae (or ?Elasmosauridae) Late Cretaceous (Maastrichtian) SA.
Attenborosaurus Bakker 1993 "Attenborough's lizard"
((David) Attenboro(ugh) + Gr. sauros "lizard") (m) named
"in honor of the naturalist and filmmaker David Attenborough, whose
childhood fascination with Liassic plesiosaurs sparked a brilliant career in
scientific journalism"; proposed for "Plesiosaurus" conybeari
Sollas 1881. The original specimen was a nearly complete skeleton with skull,
lacking most of the tail vertebrae. The fossil was found in
Vertebrae: 36 cervicals / 3 pectorals / 20 dorsals / ?4 sacrals / ?30
Length: (estimated) 5 m. (16.6 ft.); skull: 45 cm. (17 in.); mandible: 50 cm. (20 in.))
Type Species: Attenborosaurus conybeari [kon-i-BEER-ie] (Sollas 1881): for the Reverend William Conybeare (1787-1857), British paleontologist, "as a tribute to that classic authority who first made the existence and nature of Plesiosaurus known to us. This was sixty years ago; and it is singular that up to this date no one seems to have thought of calling some species of Plesiosaurus after the author of the genus." (Sollas 1881) Plesiosauroidea Early Jurassic (Sinemurian) Eur.
Bathyspondylus Delair 1982 "deep vertebra"
(Gr. bathys "deep" + Gr. spondylos "vertebra")
(m) referring to vertebrae with centra that are very deep in relation to their
length, described as "very short antero-posteriorly" and "possess
flat or incipiently concave terminal faces." An unusual, poorly known small
form from Wiltshire
Vertebrae: ?21+ cervicals
Length: (estimated) 2 m.+ (7 ft.+)
Type Species: Bathyspondylus swindoniensis [swin-doh-nee-EN-sis]
Delair 1982 "from Swindon (
Bishanopliosaurus Dong 1980 "
(Bishan (Chin. bi "wall" + Chin. shan
"mountain") + Gr. pleion "more" + Gr. sauros
"lizard") (m) named for Bishan ("
Length: (estimated) 4 m. (13.3 ft.)
Type Species: Bishanopliosaurus youngi [YUHNG-ie] Dong 1980:
for Chung Chien Young [Yang Zhongjian] (1897-1979), a famous Chinese
paleontologist. Pliosauroidea Early Jurassic (Toarcian) EAs. (
Brachaucheniidae Williston 1925 "Brachauchenius [short-neck] family"
BRAK-aw-kee-NIE-i-dee Pliosauroids in which the neck is very short (12-13 vertebrae, including atlas/axis), with single-headed ribs; Kronosaurus is currently under review and a revised description is due. Members: Brachauchenius (type), Kronosaurus
Brachauchenius Williston 1903 "short neck"
brak-aw-KEEN-ee-uhs (Gr. brakhys "short" + Gr. aukhen "neck" + -ius) (m) named to indicate "the shortest-neck plesiosaur known" at the time, with only 11 very short neck vertebrae in addition to the atlas/axis, in a neck only about 75% as long as the skull. The cervical vertebrae lack the ventral foramina (openings) found on most other plesiosaur vertebrae and support single-headed ribs (Pliosaurus had doubled-headed cervical ribs). The skull is distinctive for its broad, triangular, mosasaur-like shape, ending in a point, unlike other large pliosaurs such as Liopleurodon and Pliosaurus, which have skulls that taper abruptly in front of the nostrils into a narrow blunt snout. The large teeth have striations that branch toward the root, unlike the straight grooves on the teeth of Jurassic pliosaurs. Known from three nearly complete skulls with mandibles, and two partial skeletons (the holotype (USNM 4989) preserves 35 presacral vertebrae with ribs). Brachauchenius is a very large form (estimated to reach up to 11 m. (36.5 ft.) long based on a 1.53 m. skull (FHSM VP321)), and thus one of the last of the great mega-predator pliosaurs, dating from the Cenomanian-Turonian (early Late Cretaceous).
Vertebrae: 13 cervicals / ?2 pectorals / 20+ dorsals
Length: (estimated) up to 11 m. (36.5 ft.); skull: up to 1.53 m. (5 ft.)); mandible: up to 1.84 m (6.1 ft.)
Type Species: Brachauchenius lucasi [LOO-ka-sie] Williston 1903: for Frederick Augustus Lucas (1852-1929), at the U.S. National Museum (Smithsonian) "who has does much valuable work in American paleontology." Pliosauroidea Brachaucheniidae Late Cretaceous (Cenomanian- Turonian) NA.
Brancasaurus Wegner 1914 "Branca's lizard"
((W. v.) Branca + Gr. sauros "lizard") (m) named to
honor Wilhelm von Branca (1844-1928), noted German paleontologist; for a small,
primitive elasmosaur known from a fairly complete skeleton with skull found at
Gronau, Westphalia, west-central
Vertebrae: 37 cervicals / 3 pectorals / 19 dorsals / 3 sacrals / 25+
Length: (estimated) 3.6 m. (12 ft.); skull: (estimated) 26 cm. (10.6 in.))
Type Species: Brancasaurus brancai [BRAHNG-ka-ie] Wegner 1914: for Wilhelm von Branca (1844-1928), German paleontologist. Plesiosauroidea Elasmosauridae Early Cretaceous (Berriasian) Eur.
Brimosaurus Leidy 1854 "strong lizard"
BRIEM-o-SAWR-uhs (Gr. brime "strength" + Gr. sauros "lizard") (m) alluding to very large size of two apparent neck vertebrae that indicate a plesiosaur with a relatively short neck. Welles (1952) suggested Brimosaurus is a synonym of Cimoliasaurus. Plesiosauria i.s. Late Cretaceous NA. [nomen dubium]
Callawayasaurus Carpenter 1999 "Callaway's lizard"
KAL-uh-way-uh-SAWR-uhs (Callaway + Gr. sauros) (m) named to honor Jack M. Callaway (1930-1997), "who in his brief career as a vertebrate paleontologist, did much to improve our understanding of marine reptiles"; for "Alzadasaurus" colombiensis Welles 1962, known from a nearly complete skeleton with crushed skull (Holotype: UCMP 38349), found in the Paja Formation (Upper Aptian), near Villa de Leiva, Provincia Boyaca, Colombia; a second referred specimen found nearby is less robust than the holotype, but also is an adult, possibly indicating a sexual difference. External nares elongate in shape, positioned over maxillary teeth 3-5. A rather primitive elasmosaurid with 56 relatively short neck vertebrae. Holotype found with about 100 gastroliths.
Vertebrae: 56 cervicals / 2 pectorals / 23 dorsals / ?4 sacrals / ?28
Length: (estimated) 7.4-8 m. (25-26 ft.); skull: 34 cm. (1.3 ft.)
Type Species: Callawayasaurus colombiensis [ko-lom-bee-EN-sis]
(Welles 1962): "from
Ceraunosaurus Thurmond 1968 "thunderbolt lizard"
(Gr. keraunos "thunderbolt" + Gr. sauros
"lizard")* (m) alluding to the long, narrow shape of the skull; known
from a nearly complete skeleton with a damaged skull, found in the Lake Waco
Formation (Cenomanian) of
Cimoliasauridae Delair 1959 "Cimoliasaurus [Cretaceous-lizard] family"
si-MOH-lee-uh-SAWR-i-dee (masc. plural) A few researchers have recognized a distinct group of plesiosaurs (Mesodira) with necks intermediate in length between typical plesiosauroids and pliosauroids, though the evidence remains scrappy and difficult to interpret. Persson (1960) defined the Cimoliasauridae as: "A family in the Plesiosauroidea with neck relatively shorter than in the Plesiosauridae and the Elasmosauridae. Teeth of the general Plesiosaurian type (crowns high and slender). The height of at least the middle and posterior cervical centra approximately equal to the length, but the breadth of these centra considerably greater than the length; the end faces of the centra flat or slightly concave. Ribs single-headed." He initially included the poorly documented genera Cimoliasaurus and Scanisaurus in the family, but later revised the definition to accommodate Aristonectes as well. Currently, most scholars reserve judgment concerning "cimoliasaurs," pending discovery and description of better and more complete material.
Cimoliasaurus Leidy 1851 "Cretaceous lizard"
si-MOH-lee-uh-SAWR-uhs (Gr. kimolia "white chalky earth" [Cretaceous] + Gr. sauros "lizard") (m) named for the Late Cretaceous age of the Green Sand deposits in Burlington County, New Jersey in which the 13 type vertebrae (ANSP 9235) were found. Cimoliasaurus remains a poorly known form. No skull has been found, though various researchers have considered its neck vertebrae diagnostic: the centra are broader than long, much shorter than the corresponding centra of typical long-necked plesiosauroids but also distinct from the neck bones of pliosauroids, being somewhat longer with cervical ribs fused to the neck vertebrae and with end-faces that are nearly flat. Attributed teeth are described as high, slender and recurved.
Lydekker (1889) redefined the genus and assigned many species of Late Jurassic and Cretaceous plesiosaurs from around the world to Cimoliasaurus (which he respelled "Cimoliosaurus"), based on such general similarities as neck vertebrae with single-headed ribs and a number of features in the front limb-girdles. His redefinition of the taxon and wholesale usage of the generic name were eventually rejected by other authors. Those who still recognized Cimoliasaurus as a definable taxon saw it as much more restricted genus. (See additional comments under Crymocetus.) Despite the scrappy nature of Leidy's type specimen, Welles (1952) and Persson (1960) concluded that Cimoliasaurus belonged to a third type of Cretaceous plesiosaur (Mesodira), with necks intermediate between elasmosaurs and pliosaurs at about two to three times the length of the skull. Welles considered Cimoliasaurus a probable polycotylid. Persson, however, supported use of the separate family Cimoliasauridae (1960), classified as a branch of the Plesiosauroidea, and later included the genera Scanisaurus and Aristonectes.
Because specimens now identified as Cimoliasaurus all lack a skull or
any well preserved limb girdles, most modern researchers prefer to treat the
genus as a nomen dubium that cannot be defined in a scientifically useful way.
It was evidently a rather large plesiosaur, though exactly how many neck
vertebrae it had is not known. Welles (1952) suggested the animal was about
twice as large as Polycotylus based on North American material. A smaller
species has been proposed based on material from
Length: (estimated) ?8 m. (?29 ft.)).
Type Species: Cimoliasaurus magnus [MAG-nuhs] Leidy 1851 "large": to indicate a "giant saurian." Plesiosauroidea Late Cretaceous (Santonian) NA., ?Aus., ?Eur. [? nomen dubium]
Colymbosaurus Seeley 1874 "diving lizard"
ko-LIM-bo-SAWR-uhs (Gr. kolymbo "dive" + Gr. sauros "lizard") (m) named to indicate a swimming reptile; for "Plesiosaurus" trochanterius Owen 1840. Colymbosaurus is based on a five incomplete skeletons and some isolated limb bones (propodials) from the Kimmeridge Clay in Oxfordshire. It is the longest and most massive of all English plesiosauroids, with vertebrae similar in shape and proportions to those of Cryptoclidus. The neck (proportionately about a third longer than in Cryptoclidus) is lengthened only by an increased number of vertebrae, not by the additional lengthening of the individual neck vertebrae themselves as in Muraenosaurus or Microcleidus. Colymbosaurus has been classified as an elasmosaurid because of its long neck, but the skull is poorly known. Brown, Milner and Taylor (1986. Bulletin of the British Museum of Natural History (Geology) 40(5):225-234) suggest Kimmerosaurus (known only from a few vertebrae, and a lightly built, delicate skull rather similar to Cryptoclidus with a dense arrangement of thin teeth to trap soft- bodied prey) may be a junior synonym based on the form of the neck vertebrae and its occurrence in the same Kimmeridgian deposits. If this synonymy is confirmed, Colymbosaurus would be a long-necked cryptoclidid rather than an elasmosaurid.
Vertebrae: 42 cervicals / 3 pectorals / 25 dorsals / 4 sacrals / ?26
Length: (estimated) 5-6.6 m. (16.5-22 ft.); skull (Kimmerosaurus): (estimated) 45 cm. (18 in.))
Type Species: Colymbosaurus trochanterius [troh-kan-TEER-ee-us] (Owen 1840): for "a strongly developed trochanterian ridge projecting from the outer side of the head" of the humerus and femur (Owen 1840)). (Holotype: BMNH 31787) Plesiosauroidea Cryptoclididae Late Jurassic (Kimmeridgian- Tithonian) Eur.
Crymocetus Cope 1869 "dreadful sea monster"
krim-o-SEE-tus (Gr. krymos "chill, dread" + Gr. ketos "sea monster") (n) name proposed for "Plesiosaurus" bernardi Owen 1850, which Owen based on the centrum of a large posterior neck vertebra from Sussex, England, notable for the its deeply concave ends and very large rib facets. The centrum is somewhat higher than it is long. Cope (1869) identified his new genus Crymocetus as a supposed streptosaurian "reversed lizard" (See "Streptosauria"), but misspelled the species name as "Crymocetus barnardi."
Various researchers have used the species "Plesiosaurus" bernardi
or "Cimoliasaurus" bernardi for incomplete remains of
European Cretaceous plesiosaurs that have similar deeply concave vertebrae,
though none of these authors accepted Cope's new generic name. Lydekker (1889)
transferred the species to his revised "Cimoliosaurus," with
"Plesiosaurus" ichthyspondylus, and possibly "Plesiosaurus"
balticus as synonyms. Riabinin (1909) attributed a large forelimb and paddle
found in the Char'kov region of the
NOTE: Romer (Vertebrate Paleontology (1966)) misspelled the name "Gymocetus," the garbled version of the name cited in some later books. ?Pliosauroidea Late Cretaceous (Senonian) Eur. [nomen dubium]
Cryptoclididae Williston 1925 "Cryptoclidus [hidden-clavicle] family"
KRIP-to-KLIE-di-dee (masc. plural) Plesiosauroids with broad, short skulls specialized for filter- trap feeding on small, soft-bodied prey (crustaceans, small fish); jaws have a dense arrangement of thin, interlocking somewhat curved teeth. The neck is relatively long (29-42 vertebrae); individual cervical vertebrae are moderate in length and not elongated as in elasmosaurids, with single-headed ribs. The relationship between elasmosaurids and cryptoclidids needs more study. Cryptoclidids are best known from the Late Jurassic. A number of Late Cretaceous plesiosaurs (Aristonectes, Morturneria, Shag Point plesiosaur) have broad jaws and filter- trap teeth, and have been classified as cryptoclidids, but not all researchers agree. Bardet suggests Aristonectes and Morturneria are elasmosaurids while Persson has classified Aristonectes as a "cimoliasaurid."
Members: Cryptoclidus (type), Tricleidus, Kimmerosaurus, Colymbosaurus, ?Morturneria, ?Aristonectes Undescribed Members: "Tatenektes" (a small Late Jurassic "tricleidid" from Wyoming, NA); Shag Point plesiosaur, a 7 meter- long highly derived cryptoclidid from the Late Cretaceous (Maastrichtian) of New Zealand, with a much longer neck (more vertebrae) than Jurassic forms (to be described by Fordyce and Cruickshank).
Cryptoclidus Seeley 1892 "hidden clavicle"
KRIP-to-KLIE-duhs (Gr. kryptos "hidden" + Gr. kleid- (kleis) "key, clavicle" + -us) (m) named for the small clavicle bones that rest in "shallow depressions" on the inner surface of the scapular symphysis of the front limb girdle, and are thus "entirely hidden from view" from below (Seeley 1892, Proceedings of the Royal Society of London 51: 139). Proposed for "Plesiosaurus" eurymerus Phillips 1871, a taxon originally based on a forelimb notable for a humerus that widens at the bottom-- the limb was mistaken at first for a hindlimb, thus the misleading species name eurymerus "wide femur." Seeley's type specimen is now lost. Brown (1981) designated a neotype (BMNH R.2860) for Cryptoclidus eurymerus in the British Museum of Natural History--one of the most complete adult skeletons of a plesiosaur ever found, described by Andrews in 1910. Brown (1981) also declared the name Cryptoclidus oxoniensis (used by many authors as the type species) a nomen dubium based on a non- diagnostic vertebra ("Plesiosaurus" oxoniensis Phillips 1871).
Cryptoclidus is among the best documented of all plesiosaurs, known from many specimens, including adults and juveniles. The skull is relatively broad, rather lightly built, and notable for the dense arrangement of thin, sharply inclined outward pointing teeth that intermeshed when the jaws met. There were 24-27 teeth on each ramus of the mandible for approximately a hundred total in the entire mouth. Cryptoclidus probably fed on schools of soft-bodied cephalopods and small fish, using its many teeth as a filter or trap--its lightly built skull and jaws were not designed to resist strong twisting forces generated by biting or tearing prey. The small size of its external nasal openings and the forward position of the internal nares on the roof of its mouth have suggested to some researchers (Brown & Cruickshank 1994) that its nostrils were not used for breathing, but for "smelling" underwater--Cryptoclidus would have passed water through the internal nares on the roof of its mouth, then up and out its nose to detect chemical traces of prey.
Vertebrae: 29-32 cervicals / 3 pectorals / 20-23 dorsals / 4 sacrals /
Length: 3-4 m. (10-13 ft.); skull: 22 cm. (9.4 in.); mandible: 25.4 cm. (10.25 in.)
Type Species: Cryptoclidus eurymerus [yoor-i-MEER-uhs] (Phillips 1871) "wide femur": for a humerus that widens at the bottom--the namesake limb bone was originally mistaken for a hindlimb, thus the misleading species name eurymerus "wide femur."
Additional species: Cryptoclidus richardsoni [RICH-ahrd-SOH-nie] (Lydekker 1889) for Nelson M. Richardson of Dorset, who collected the specimen (nearly complete skeleton without skull); differs in shape of humerus, which is not expanded at the front bottom end.
NOTE: Cryptoclidus oxoniensis [ok-soh-nee-EN-sis] (Phillips 1871) "from Oxford, England," often cited as the type species, was declared a nomen dubium by Brown (1981), who made redefined Cryptoclidus eurymerus the type species based on a neotype specimen (BMNH R.2860). Plesiosauroidea Cryptoclididae Late Jurassic (Callovian) Eur.
Discosaurus Leidy 1852 "disk (vertebra) lizard"
DIS-ko-SAWR-uhs (Gr. diskos "discus" + Gr. sauros "lizard") (m) named for the round shape of an isolated tail vertebra. Welles (1962) suggested it was pliosaurian. Plesiosauria i.s. Late Cretaceous NA. [nomen dubium]
Dolichorhynchops Williston 1902 "long snout face"
DOL-i-ko-RING-kops (Gr. dolikhos "long" + Gr. rhygkhos "snout, beak" + ops "face") (m) named for the "remarkably elongate and slender form" of the skull, with "the facial region much attenuated," resulting in a narrow, elongated snout, reminiscent of ichthyosaurs; known from a number of complete adult skeletons with skulls, as well as partial skeletons and skulls of juveniles.
Studies by Ken Carpenter (1996: Neues Jahrbuch fuer Geologie und
Palaeontologie. Abhandlungen. 201 (2): 259-287) indicate Dolichorhynchops
is a definable genus distinct from the geologically earlier Trinacromerum,
often considered a synonym. Carpenter differentiated the two genera based in
part on the form of their teeth (slender and finely ridged in Dolichorhynchops;
robust and coarsely ridged in Trinacromerum), and the shape of the
temporal openings in the skull (short and wide in Dolichorhynchops; long
and narrow in Trinacromerum). The two genera also occur in different
stratigraphic ranges in the interior of western
Vertebrae: 19 cervicals / 3 pectorals / 23-24 dorsals / 3 sacrals /
Length: 3-5 m. (10-17 ft.); skull: 52-98 cm. (17-39 in.); mandible: 56-102 cm. (20-41 in.).
Type Species: Dolichorhynchops osborni Williston 1902 "in honor of Prof. H[enry] F[airfield] Osborn of Columbia University" (Holotype: KUVP 1300); Synonyms: Trinacromerum osborni; Trinacromerum bonneri.
NOTE: "Trinacromerum bonneri"
Dravidosaurus Yadagiri & Ayyasami 1979 "Dravidian lizard"
dra-VID-o-SAWR-uhs (from Dravidandu + Gr. sauros "lizard") (m) named for Dravidandu, the region of the southern Indian peninsula, where the fossil was found. The fragmentary specimen consisted of bones originally misidentified as armor plates supposedly belonging a very small stegosaurian dinosaur. Chatterjee and Rudra (1996: Memoirs of the Queensland Museum 39(3): 489-532) reidentified the remains as highly weathered limb and girdle elements that probably belong to plesiosaurs. Plesiosauria Late Cretaceous India [nomen dubium]
Edgarosaurus Druckenmiller 2002 "Edgar (
(Edgar + Gr. sauros "lizard") (m) named to indicate a
plesiosaur found near the community of Edgar, in
Type Species: Edgarosaurus muddi [MUH-die] Druckenmiller
2002: in memory of Kevin Mudd of
Elasmosauridae Cope 1869 "Elasmosaurus [plate-lizard] family"
e-LAS-mo-SAWR-i-dee (masc. plural) Plesiosauroids with very long necks (32-72 vertebrae); individual cervical vertebrae are typically more elongated than in other plesiosaurs, particularly in the anterior region of the neck. Late Jurassic and Cretaceous forms have single-headed cervicals ribs. Traditionally, most authors have used this family for all forms with very long necks, but new research has begun to complicate the picture. The family may date back to the Early Jurassic (Eretmosaurus) (Bardet 1995). Colymbosaurus and Tricleidus, once considered elasmosaurs (Brown 1981), now appear to be a long-necked cryptoclidids (Brown 1993). Bakker (1993) has argued that Cretaceous elasmosaurs (from Brancasaurus on), evolved separately from pliosaurs similar to Leptocleidus and are not closely related to long-necked Late Jurassic forms such as Muraenosaurus, making the traditional version of Elasmosauridae an unnatural group. Carpenter (1996, 1997), by contrast, has retained the traditional Elasmosauridae (including Jurassic forms) and revised the short-necked polycotylids as a family of plesiosauroids closely related to elasmosaurids (see Polycotylidae below). The incompletely known Late Cretaceous Artistonectes and Morturneria have skulls with filter-trap jaws similar to cryptoclidids, but have been placed in the Elasmosauridae by Bardet (1995).
Jurassic elasmosaurids differ from Cretaceous elasmosaurids in a range of features, but most notably the construction of the front limb girdle. Jurassic forms, like all other types of plesiosaurs, have scapulae that are proportionately much smaller than the coracoids. In contrast, many Late Cretaceous elasmosaurids have well-developed scapulae, indicating muscles that could power a strong backing stroke, making the animals highly maneuverable. In Cretaceous elasmosaurs the right and left coracoids meet along the animal's midline then separate toward the back to form a scooped-out, roughly heart-shaped opening--Jurassic elasmosaurids and other types of plesiosaurs lack this rounded separation in the front limb girdle.
Members: Elasmosaurus (type), ?Eretmosaurus, Microcleidus,
Muraenosaurus, Brancasaurus, Woolungasaurus, Alzadasaurus,
Aphrosaurus, Fresnosaurus, Hydralmosaurus, Hydrotherosaurus,
Leurospondylus, Libonectes, Mauisaurus, Morenosaurus,
Styxosaurus, Thalassomedon, Tuarangisaurus, (?Aristonectes,
?Morturneria) Undescribed members: Courtenay Museum elasmosaurid, a very
large elasmosaurid (est. 10 m. (34 ft.)) discovered on the Puntledge River west
of Courtenay on eastern Vancouver Island, British Columbia; probably a new
genus, although study of the specimen has not been completed. Its lower jaw is
large for an elasmosaur (about half a meter in length). "Elasmosaurus"
amalitskii Pravoslavlev 1914, from the Turonian of the
Elasmosaurus Cope 1868 "plate (bone) lizard"
(Gr. elasma "metal plate" + Gr. sauros
"lizard") (m) "called Elasmosaurus...from the...great
plate bones of the sternal and pelvic regions" (Cope 1868: Proceedings of
the Academy of Natural Sciences Philadelphia (v. 20)). (Contrary to some
sources, the name Elasmosaurus does NOT mean "ribbon lizard" or
"swan lizard.") The "plate bones" on the underside of the
animal consisted of flattened scapulae and coracoids that braced the front
limbs, and wide flattened pubes and ischia that braced the hind limbs. Cope
originally misinterpreted the scapula bones as "pubes" (Transactions
of the American Philosophical Society 1869 (withdrawn and republished)), but
later "corrected" his analysis (TAPS 1870 corrected version), and
re(mis)identifed the scapula bones as "clavicles." Regrettably, the
original fossil "plate bones" that inspired the name Elasmosaurus
are now lost from the type material remaining in the
According to the original 1868 description, Cope's creature's
"propulsion was more largely accomplished by its tail than by its
paddles"--but the "tail" referred to was really Elasmosaurus'
spectacular long neck! In a notorious scientific blunder, Cope had mistakenly
attached the animal's head to the end of the true tail. He then erected a new
reptilian order, Streptosauria "reversed lizards," to accommodate his
odd creature --"streptosaurs" resembled plesiosaurs except that all
their vertebral articulations were backward! (See additional comments at
"Streptosauria.") The type species name Elasmosaurus platyurus
"flat-tailed" immortalizes Cope's error--the "enormous and
flattened tail" that he characterized in the species name was based on NECK
bones with high neural arches along the top. O. C. Marsh "gently"
pointed out Cope's anatomical juggling when he saw the specimen during a visit
The extraordinary long neck had around 72 cervical vertebrae, a record for vertebrates, and is the longest neck in both relative and absolute terms for any plesiosaur. (The sauropod dinosaur Mamenchisaurus had the longest neck of any known animal at an estimated 13.1 m. (46 ft.) for the largest species (Mamenchisaurus sinocanadorum), but its neck was composed of "only" 19 cervical vertebrae. Some supergiant sauropods from the Late Jurassic of North America (Seismosaurus, Supersaurus, Amphicoelias) may have had even longer necks on proportionately much larger bodies, but adequate skeletons to directly confirm this fact are lacking.)
Elasmosaurus's long neck anchored a surprisingly small head. The type skull was incomplete, consisting of part of a snout with thin teeth and a small occipital condyle; the somewhat more robust head shown in many modern restorations is based on a different specimen now identified as Styxosaurus snowii. Remains of the pelagic predatory ctenoid fish Enchodus were found under the dorsal ribs of the type specimen, leading Cope to conclude that, "The most ravenous fish--the Enchodi, or great barracudas of the Cretaceous, were his food." It thus appears, that despite its small head, Elasmosaurus could catch and swallow fast swimming prey thanks to a wide gape and sharp spike-like teeth.
Ken Carpenter (1997) has restricted the genus Elasmosaurus to its type species Elasmosaurus platyurus, known from the single, incomplete specimen in the Philadelphia Academy of Natural Sciences (ANSP 10081). Other named species of Elasmosaurus either have been redescribed as new genera (E. morgani = Libonectes, E. serpentinus = Hydralmosaurus, E. snowii = Styxosaurus) or need to be revised ("Elasmosaurus" amalitskii).
Vertebrae: 72 cervicals / 5 pectorals / ?18 dorsals / 6 sacrals / ?21
Length: (estimated) 11-12 m. (37-42 ft.); skull: (estimated) ?40 cm. (16 in.)
Type Species: Elasmosaurus platyurus [plat-ee-YOOR-uhs] Cope 1868 "flat-tailed": referring to the "enormous and flattened tail"-- Cope mistakenly put the animal's head on the tip of its real tail, and the supposed tail cited in the species name actually the animal's neck! Plesiosauroidea Elasmosauridae Late Cretaceous (Campanian) NA.
Embaphias Cope 1894 "saucer (vertebrae)"
(Gr. embaphion "saucer" + -ias "in character")
(m) named for the saucer-like shape of its concave vertebrae; for three
vertebrae from the Pierre Shale of
Eretmosaurus Seeley 1874 "oar lizard"
(Gr. eretmos "oar" + Gr. sauros
"lizard") (m) referring to the powerful limb paddles found in
plesiosaurs. Scientists in Seeley's day assumed that plesiosaurs
"rowed" with their large paddle-like limbs; modern research indicates
plesiosaurs swam more like sea lions, using a modified form of underwater
"flight." Proposed for "Plesiosaurus" rugosus
("rugose") Owen 1840, a form originally based on isolated vertebrae
with rugged surfaces on the centra except on the concave ends, which were
smooth. Although this "rugose" appearance is found on the vertebrae of
some other types of plesiosaurs and is not diagnostic, Owen used the same
species name for a nearly complete, but headless, long-necked plesiosaur
skeleton in the
Based on its long neck, Bardet (1995) suggests that Eretmosaurus is the earliest known elasmosaurid, although the individual neck vertebrae are not elongated as in later elasmosaurids. Other classifications have listed Eretmosaurus as a plesiosaurid or as a pliosauroid (Brown 1981).
Vertebrae: 35+ cervicals
Length: (estimated) 4-5 m. (14-17 ft.)) (skull not known)
Type Species: Eretmosaurus rugosus [ruh-GOH-suhs] (Owen 1840) "rugose": "distinguishable from all other vertebrae by the peculiarly rugous character of the free or non-articular surfaces of the body." (Owen 1840)) Plesiosauroidea ?Elasmosauridae Early Jurassic (Sinemurian) Eur.
Eurycleidus Andrews 1922 "wide clavicle"
YOOR-i-KLIE-duhs (Gr. eurys "wide" + Gr. kleid- (kleis) "key, clavicle" + -us) (m) alluding to a large clavicular arch similar in form to that of Leptocleidus "but the interclavicle is wider"; for "Plesiosaurus" arcuatus Owen 1840. Based on an incomplete skeleton, and parts of a skull and a lower jaw (the part made the holotype: BMNH 2030). Total tooth count not known, but on each side of the lower jaw at least five large, procumbent teeth in the front, with at least 22 much smaller teeth behind. The neck vertebrae have long centra (a plesiosauroid characteristic), but the skull is large and broad, and the front limb girdle has long coracoids (pliosauroid characteristics). Some authors (Storrs & Taylor 1996) have considered Eurycleidus arcuatus a probable synonym of Rhomaleosaurus megacephalus. However, Cruickshank (1994. Zoological Journal of the Linnaen Society 112:151-178) has identified a juvenile specimen of Eurycleidus that supplies additional information about the taxon. If the identification is correct, Eurycleidus had a mosaic of cranial features found in plesiosauroids (arrangement and shape of bones at the back of the skull and back of the lower jaw) and pliosauroids (large teeth in the front of the jaw and a long symphysis with at least 4 tooth positions), making it a distinct genus that shows a mixture of features traditionally used to separate the Plesiosauria into two superfamilies Plesiosauroidea and Pliosauroidea. Its "intermediate" appearance in turn raises questions about the current system for classifying early plesiosaurs. Eurycleidus was probably a generalist feeder that preyed on soft-bodied animals such as belemnites, small fish and ammonites.
Length: (estimated) 4 m. (13-14 ft.); skull: (estimated) 25.5 cm (10 in.); mandible: 35 cm. (13 in.))
Type Species: Eurycleidus arcuatus [ahr-koo-AY-tuhs] (Owen 1848) "curved," for Plesiosaurus arcuatus Owen 1840, in apparent reference to the "nearly circular" contour of the articular surface on the body of the vertebrae, contrasting with the "triangular form" of the centra of the vertebrae in "Plesiosaurus" subtrigonus Owen 1840.
NOTE: The species Eurycleidus megacephalus proposed by Andrews in 1922 for "Plesiosaurus" megacephalus Stutchbury 1846, and still recognized by some authors, was classified as Rhomaleosaurus megacephalus by Cruickshank (1994). (See Rhomaleosaurus)). ?Pliosauroidea Early Jurassic (Hettangian) Eur.
Eurysaurus Gaudry 1878 "broad lizard"
YOOR-i-SAWR-uhs (Gr. eurys "wide, broad" + Gr. sauros "lizard")* (m) so-named "because the animal must have had a very broad head and body," based on the large proportions of preserved parts of its skull; type material (cranium, teeth and 5 vertebrae) from Echenoz-la-Meline, France, is now lost. Pliosauroidea Early Jurassic Eur. [nomen dubium]
Fresnosaurus Welles 1943 "
Length: Adult size unknown but estimated by Welles (1943) to be "very large" (35+ ft.) from the massive proportions of the juvenile.
Type Species: Fresnosaurus drescheri [DRESH-uhr-ie] Welles 1943 : for Arthur Drescher, "who was in charge of collecting the Pasaena plesiosaurs." (Holotype: CIT 346) Plesiosauroidea Elasmosauridae Late Cretaceous (Maastrichtian) NA.
Georgia Ochev 1976 "for Georgy (Ochev)"
gay-OR-gee-uh (Georgii + -ia) (f) named to honor V. A. Ochev's father, Georgy Ochev, a geodesist, whose death coincided with his son's work on describing the specimen from Penza Province, in the Volga Region of Russia. (V.A. Ochev, personal communication). NOTE: In principle, the "g" would be pronounced hard in a Russian-derived name. (Preoccupied by Georgia Baird & Girrard 1853; see Georgiasaurus) [= Georgiasaurus]
Georgiasaurus Ochev 1977 "Georgy's lizard"
gay-OR-gee-uh-SAWR-uhs (Georgii + -ia + Gr. sauros "lizard") (m) named to honor V. A. Ochev's late father, Georgy Ochev (replacement for preoccupied Georgia Ochev). Originally a complete skeleton, the specimen was damaged in preparation of the quarry stone. Poorly preserved bones left impressions and cavities in the matrix that indicate a plesiosaur with clear resemblances to the narrow-skulled Trinacromerum, but with a relatively shorter skull.
Length: (estimated) 4-5 m. (13-16 ft.); skull: (estimated) 70 cm. (28 in.))
Type Species: Georgiasaurus penzensis [pen-ZEN-sis] Ochev, 1977
NOTE: The generic name Georgiasaurus has NO connection with the
country (and former
Halidracon Wagler 1830 "sea dragon"
ha-LID-ra-kon (Gr. halis "sea" + Gr. drakon "dragon") (m) for an animal belonging to the Gryphi, erected by Wagler for marine animals supposedly between mammals and birds. [= Plesiosaurus]
Hauffiosaurus O'Keefe 2001 "Hauff (Museum) lizard"
(Hauffius + Gr. sauros "lizard") (m) named for the Hauff
Museum (Urwelt-Museum Hauff) in Holzmaden, Baden-Wuerttemberg, Germany, where
the type specimen is housed; the private Hauff Museum was established by Dr.
Bernhard Hauff (1866-1950), who prepared fossils found in the famous Holzmaden
slate quarries of southern Germany. Hauffiosaurus is a relatively small
(2.5 m (8.3 ft) long) pliosaurid known from a complete skeleton (Holotype:
uncatalogued specimen in
Skull: 43 cm (17.2 in) long
Vertebrae: 28-30 cervicals/(probably around ?5 pectorals/ ?20 dorsals /?4 sacrals / ?30 caudals)
Length: 2.5 m (8.3 ft).
Type Species: Hauffiosaurus zanoni [ZAN-o-nie] O'Keefe 2001: for the American paleontologist Robert Thomas Zanon (1957-1990) "who first realized this specimen represented a new genus." Pliosauroidea Pliosauridae Early Jurassic (Toarcian) Eur. [added 6-2002]
Hexatarsostinus Hawkins 1840 "six-tarsal boned"
HEK-sa-tar-SOS-tin-uhs (Gr. hexa "six" + Gr. tarsos "tarsus" + Gr. ostinos "bony") (m) named for the construction of its paddles, with extra bones. Plesiosauria i.s. Early Jurassic Eur. [nomen dubium]
Hydralmosaurus Welles 1943 "salt water lizard"
hie-DRAL-mo-SAWR-uhs (Gr. hydralme "salt water" + Gr. sauros "lizard")* (m) named to indicate a sea-going elasmosaurid; proposed for "Elasmosaurus" serpentinus Cope, 1877, based on a nearly complete skeleton (lacking skull) from Nebraska (Holotype: AMNH 1495); notable for a massive humerus, indicating a powerful swimmer. Carpenter (1999: Paludicola 2(2)) includes Styxosaurus browni Welles 1952 (partial skeleton with skull: AMNH 5835) as a junior synonym of the type species, based on the distinctive posterior expansion on the distal end of the humerus not found in other types of elasmosaurids. The skull has external nares that are elongate in shape.
Vertebrae: 63 cervicals / 3 pectorals / 19 dorsals / 4 sacrals /
Length: (estimated) 11 m. (38 ft.); skull: 37 cm. (15 in.)
Type Species: Hydralmosaurus serpentinus [ser-pen-TIEN-uhs] (Cope 1877) ("serpentine" for its long neck). (Synonyms: Styxosaurus browni Welles 1952.) Plesiosauroidea Elasmosauridae Late Cretaceous (Santonian-Campanian) NA. (revised 7/99)
Hydrotherosaurus Welles 1943 "fisher lizard"
hie-dro-THEER-o-SAWR-uhs (Gr. hydrotheras "fisherman" + Gr. sauros "lizard")* (m) named to indicate "an active piscivore with long, flexible neck"; fish vertebrae were found among its gastroliths, confirming its diet. Hydrotherosaurus was a coast- dweller, known from a complete skeleton with skull (Holotype: UCMP 33912) from the Maastrichtian Moreno Formation, Panoche Hills, Fresno County, California, and notable for vertebrae that are relatively lower and narrower at the anterior end, but broader and higher toward the base compared with other elasmosaurs. In restoring Hydrotherosaurus, Welles gave the ribs a raking angle, slanted backward as in crocodiles, resulting in a narrower, more streamlined body. Welles argued that the traditional broad, turtle-like reconstruction of the plesiosaur trunk with ribs projecting nearly straight out is incorrect and a misinterpretation based on post-mortem crushing of the skeletons.
Vertebrae: 60 cervicals / 2 pectorals / 17 dorsals / 3 sacrals / ?30
Length: (estimated) 12.75 m. (42 ft.); skull: 33 cm. (13 in.)
Type Species: Hydrotherosaurus alexandrae [al-eg-ZAN-dree]
Welles 1943: for Annie Montague Alexander (1867-1950), a fossil collector and
science patron who "contributed so much to the work of the vertebrates of
the West" through her work with and support for the
Ischyrodon von Meyer 1838 "strong tooth"
(Gr. iskhyros "strong" + Gr. odon
"tooth") (m) for a very large tooth from
Kaiwhekea Cruickshank & Fordyce 2002 "squid-eater"
(Maori kai "eat" + Maori wheke "squid,
octopus" + -a) (f) named to indicate a squid-eating plesiosaur from
Skull: 62 cm (24.8 in) long
Vertebrae: 43 cervicals/ 3 pectorals /19-20 dorsals / 3-4?sacrals/ (probably around 25-30 caudals)
Length: 6.5+ m (22 ft)
Type Species: Kaiwhekea katiki [KUH-ti-kee] Cruickshank
& Fordyce 2002: for
Kimmerosaurus Brown 1981 "Kimmeridge lizard"
KIM-uhr-o-SAWR-uhs (Kimmer(idge) + Gr. sauros "lizard") (m) named for the stratigraphical horizon of the type specimen (a partial skull): Kimmeridgian Stage, Kimmeridge Clay, at Dorset, England; known from three partial skulls with mandibles, and a few neck vertebrae, including the atlas/axis. The skull is broad, but very lightly built, and more elongated than in Cryptoclidus. The teeth are highly recurved, thin, sharply pointed, with 36 in each side of the lower jaw, indicating a trap-feeder on relatively small, soft prey. The axis/atlas and neck vertebrae are similar to Colymbosaurus, a genus found in the same deposits. Colymbosaurus is only known from skeletons without a skull, and the skull of Kimmerosaurus could very well belong to Colymbosaurus, making Kimmerosaurus a junior synonym (Brown, Milner & Taylor, 1986). See additional comments at Colymbosaurus.
Length: skull: (estimated) 22 cm. (17 in.); mandible (estimated) 30 cm. (12 in.)
Type Species: Kimmerosaurus langhami [LANG-uhm-ie] Brown 1981
for "R. A. Langham, Esq., of
Kronosaurus Longman 1924 "Kronos lizard"
KRON-o-SAWR-uhs (Kronos, a Titan in Greek mythology + Gr. sauros "lizard") (m) named for Kronos, a mythical giant Titan who ruled the universe before his son Zeus overthrew him; alluding to the animal's huge size and fierce appetite--Kronos swallowed his own children shortly after each was born to prevent any of them from deposing him. His efforts failed when his wife Rhea hid the infant Zeus and substituted a rock wrapped in swaddling to deceive her cannibalistic husband.
Although widely illustrated and discussed in popular books, the genus Kronosaurus
remains problematical. The name Kronosaurus queenslandicus was
originally proposed by Heber Longman in 1924 for poorly preserved but very large
lower jaw fragments found near Hughendend, Queensland, Australia in 1899
(Holotype: QM F1609). Gigantic but fragmentary limb elements discovered in 1929
were described in 1932, with part of a humerus indicating an animal larger than Megalneusaurus.
A Harvard expedition in 1931- 1932 recovered two specimens of large plesiosaurs
in another region of Queensland: a giant incomplete skeleton, removed in part by
dynamiting, from Army Downs, 35 miles north of Richmond, Queensland; and the
rostrum (with upper and lower jaws) of a smaller individual from Grampian
Valley, 30 miles north of Richmond. More recent finds may help clear up many
questions about the status of the genus. A nearly complete skull about 6 feet
long that was found near the same region as the type specimen jaw fragments, as
well as various parts of skeletons and limbs, and a partial skull from the
Toolebuc Formation. So far all the material appears to be consistent with a
single genus (though perhaps more than one species)--Colin McHenry of the
Complicating the picture is the precise identity of the well- known gigantic
specimen (MCZ No. 1285) in the Harvard University Museum of Comparative Zoology
(originally restored at 12.8 m. (42 ft.); revised estimated total length: 9 m.
(30 ft.); skull: originally estimated 2.9 m. (9 ft. 8. in) (likely too long)).
The Harvard kronosaur came from the older Wallumbilla Formation. Although
identified as Kronosaurus queenslandicus by White in 1935 and Romer in
1959, the famous Harvard kronosaur might be taxonomically distinct from the
Hughendend Toolebuc Formation material, at least on the species level. Settling
the issue will be difficult. Despite the spectacular appearance of the mounted
skeleton at the
The rather speculative nature of the heavily restored Harvard giant seems an
irony in view of the mount's history--funding for the preparation of the
specimen came from the wealthy Cabot family of
Vertebrae: 12 cervicals / 3 pectorals / 19-20 dorsals / 4-5 sacrals / ?31 caudals [NOTE: Romer and Price (1959) indicated that the Harvard specimen had "probably 30 dorsals"; however, Colin McHenry (personal communication) has revised the estimate down to around 20, consistent with the 19 dorsals indicated for the better preserved Kronosaurus boyacensis (Hampe 1992).]
Type Species: Kronosaurus queenslandicus [kweenz-LAN-di-kuhs]
Longman 1924 "from
Additional Species: Kronosaurus boyacensis [boy-ah-SEN-sis]
Hampe 1992: "from
Leptocleidus Andrews 1922 "thin clavicle"
LEP-to-KLIE-duhs (Gr. leptos "slender, thin" + Gr. kleid- (kleis) "key, clavicle" + -us) (m) named for the vertically "thin clavicular arch" along the edge of the front limb girdle, composed of two "rather large" clavicles and a "transversely elongated" interclavicle. Andrews (1922) thought this Early Cretaceous form retained primitive features in the well-developed clavicular arch of its shoulder-girdle, similar to Early Jurassic Liassic plesiosaurs such as Eurycleidus--an idea expressed in the Latin species name superstes "surviving, long-lived". Andrews concluded that "the retention of the primitive condition in Leptocleidus...may be a consequence of the freshwater, probably fluviatile, habitat of this Plesiosaur, which resulted in its leading a life sheltered from the great competition among the marine Plesiosaurs." Other authors (Cruickshank 1997) have found primitive features in the skull as well.
Leptocleidus somewhat resembles the Early Jurassic Rhomaleosaurus, with large clavicles and interclavicle, and small, widely separated scapulae. There are only 21 teeth on each side in the upper jaws (probably 35 teeth in each lower jaw), and indicate a generalist type predator, capable of capturing active prey, or using twist-feeding to tear flesh from a large carcass. The triangular skull has a distinctive crest along the top, running from a forward-pointing "cockscomb" at the very back to a ridge over the nasal region. Unlike early pliosauroids, Leptocleidus has single-headed cervical ribs and a deep central depression in the centra of the neck vertebrae.
Leptocleidus is similar to a modern seal in size and may have had a
similar diet and lifestyle. The genus occurs in lagoonal or shallow, close
inshore marine facies (Cruickshank 1997), though it may have frequented
freshwater environments such as lakes and rivers as well. Despite an apparently
restricted habitat, species have been identified from
Vertebrae: 13-24 cervicals / ?20 dorsals
Length: (estimated) 2-3 m. (7-10 ft.); skull: 31 cm.(12.5 in.)
Type Species: Leptocleidus superstes [suh-PER-steez] Andrews 1922 "long-lived," alluding to its retention of primitive features found in much earlier plesiosaurs. (Holotype: BMNH R4824)
Additional species: Leptocleidus capensis [kay-PEN-sis]
(Andrews 1911) "from
Leptocleidus clemai [KLEM-uh-ie] Cruickshank & Long 1997; named for John Clema, who helped sponsor the expedition that excavated the fossils. The largest known species (3 m. (10 ft.) long), based on three partial skeletons from the Birdsong Sandstone, north of Kalbarri in Western Australia. Notable for more robust femur and humerus.
NOTE: An opalized specimen about 85% complete recently found in
Leurospondylus Brown 1913 "flat vertebra"
(Gr. leuros "smooth, even, flat" + Gr. spondylos
"vertebra") (m) named "in reference to the flat vertebrae,"
contrasting with the concave-ended centra found in most other plesiosaurs. Based
on a partial skeleton (without a skull) (Holotype: AMNH 5261) of a juvenile
"plesiosaur associated with dinosaur remains high up in the brackish water
Type Species: Leurospondylus ultimus [UHL-ti-muhs] Brown 1913
"last," because it was thought to be the last occurrence of a
plesiosaur: "so far as known marks the termination of this group of
Mesozoic reptiles." (Brown 1913) However, revised dating of the Horseshoe
Canyon Formation (Gibson 1977) means that some
Libonectes Carpenter 1997 "Southwest swimmer"
LIE-bo-NEK-teez (Gr. libo- (lips) "southwest wind" + Gr. nektes "swimmer") (m) named for the American Southwest, the region in which the holotype was found (Britton Formation, Eagle Ford Group, Dallas County, Texas); proposed for "Elasmosaurus" morgani Welles 1949. The holotype material (SMUSMP 69120) now consists only of a skull (with braincase preserved), lower jaw and 62 neck vertebrae (est. length: 18.5 ft.); a large front-limb girdle (scapulae and coracoids) and part of a humerus described and illustrated by Welles were later discarded(!) by museum staff, but appear to indicate an animal with trunk and limb proportions similar to Elasmosaurus, though with a shorter neck. Libonectes differs from Elasmosaurus in the short and deep shape of the atlas/axis centrum (long and low in Elasmosaurus). The external nares are elongate in shape and located over maxillary teeth 3-4. The new generic name Libonectes was suggested by Ben Creisler.
Vertebrae: 62 cervicals
Length: (estimated) ?10 m. (?34 ft.); skull: 42.5 cm. (17 in.); mandible: (estimated) 55 cm. (22 in.)
Type Species: Libonectes morgani [MOR-ga-nie] (Welles 1949): for Charles Gill Morgan, who obtained and prepared the specimen. Plesiosauroidea Elasmosauridae Late Cretaceous (Turonian) NA. (revised 7/99)
Liopleurodon Sauvage 1873 "smooth-sided tooth"
(Gr. leios "smooth" + Gr. pleuron
"side" + Gr. odon "tooth") (m) named for a
very large tooth with contrasting sides: "one side is nearly smooth, while
the other has strong striations that run its length, the two edges being marked
by a rather prominent ridge." (Sauvage 1873) The type material consisted of
an isolated tooth found in the Oxford Clay of Wast near Boulogne-sur-Mer in
The original tooth is considered diagnostic and appears identical to teeth
found with an associated skeleton (BMNH R. 3536) in the Oxford Clay at
Vertebrae: 17-20 cervicals
Length: (estimated) 12-15 m. (39-50 ft.); skull: up to 2.2-3 m. (8-10 ft.)
Type Species: Liopleurodon ferox [FER-oks] Sauvage 1873 "fierce"; for the large size of its teeth; the largest known species, possibly reaching 15 meters (50 ft.). (Callovian)
Additional Species: Liopleurodon pachydeirus [pak-ee-DIE-ruhs] (Seeley 1869) "stout-necked": differs from Liopleurodon ferox in the form of the neck vertebrae, which are longer, with a faint keel on the underside; the longitudinal ridges on the tooth enamel are finer and more closely packed than in Liopleurodon ferox. (Callovian)
Liopleurodon rossicus [ROS-i-kuhs] (Novozhilov 1964) "Russian"; for Pliosaurus rossicus Novozhilov 1964, a large pliosaur from the Lower Volgian of the Moscow Basin, Russia, based on a skull; teeth trihedral in cross-section. (Tithonian)
Liopleurodon macromerus [mak-ro-MEER-uhs] "long femur"
(Phillips 1871). Tarlo (1959) created a new genus Stretosaurus for Pliosaurus
macromerus Phillips 1871, based on the supposedly unusual form of the
scapula. Halstead [= Tarlo] (1989) reidentified the "scapula" as an
ilium after a more complete specimen was found, and transferred the species to Liopleurodon.
However, Tarlo's 1960 definition mentions teeth that are trihedral in
cross-section, considered a characteristic of Pliosaurus. Hampe (1992)
disputed Halstead's (1989) placement of this species in the genus Liopleurodon,
and restored it to Pliosaurus. The species is also identified from
Luetkesaurus Kiprijanoff 1883 "Luetken's lizard"
(Luetken + Gr. sauros "lizard") (m) to honor Christian
Frederich Luetken (1827--1901), Danish zoologist and paleontologist; proposed
for teeth that are finely striated, and vertebrae, found in the Sewerisch
Osteolite of the
Macroplata Swinton 1930 "long blades"
ma-KROP-la-tuh or MAK-ro-PLAY-tuh (Gr. makros "long, large" + Gr. plate "a blade, and, especially in the plural, the shoulder-blades")* (f) referring to the frontlimb girdle, with "very long and comparatively narrow coracoids which have considerable preglenoidal extension"; the shoulder blades (scapulae and coracoids) were modified to form large bony plates on the underside of the body to brace the front paddles. Like other short-necked plesiosaurs, Macroplata had coracoids that were proportionately much larger than the scapulae, indicating a powerful forward stroke for fast swimming. Macroplata is a relatively primitive short-necked form, with a needle-nosed snout and a tapering, rather rigid neck a little over twice the length of the skull, made of short flattened, vertebrae.
Vertebrae: 27 cervicals / 5 pectorals / 19 dorsals / 4 sacrals / 30-32
Length: 4.5 m. (15.4 ft.); skull: 58 cm. (1.9 ft.))
Type Species: Macroplata tenuiceps [te-NOO-i-seps] Swinton 1930 "narrow headed" for the narrow, elongated, subtriangular form of its skull. (Holotype: BMNH R.5488) (Hettangian)
Additional species: Macroplata longirostris [lon-ji-ROS-tris] (Blake 1876) "long-snouted"; for "Plesiosaurus" longirostris Blake 1876, transferred to Macroplata by White in 1940; with a very long thin snout, about half the length of the entire skull and a jaw symphysis 13 tooth positions long. Some authors have included the species "Plesiosaurus" longirostris in Rhomaleosaurus; it may be revised as a new genus. (Holotype: MCZ 1033) (5 m. long; skull 70 cm. long) (Toarcian) Pliosauroidea Early Jurassic (Hettangian(-Toarcian)) Eur.
Maresaurus Gasparini 1997 "sea lizard"
(Lat. mare "sea" + Greek sauros
"lizard")* (m) named to indicate a marine pliosauroid found in the
Length: (estimated) 5-6 m. (16-20 ft.); skull: .8 m. (2.5 ft.))
Type Species: Maresaurus coccai [KOH-kah-ie] Gasparini 1997: for "the brothers Sergio and Rafael Cocca, members of the Museo Prof. Olsacher of Zapala, and valuable collaborators in all the fieldwork related to the search for marine reptiles in the Neuquen Basin." Pliosauroidea Middle Jurassic (Bajocian) SA.
Mauisaurus Hector 1874 "
(Maui (Maori demi-god) + Gr. sauros "lizard") (m) named
for Maui, a Maori demi-god and hero; to indicate a plesiosaur found in New
Zealand, home of the Maori people. Mauisaurus remains a poorly known
form, originally based on material from several localities; Welles (1962)
designated the pubes and pelvic paddle as the lectotype, indicating "a
unique plesiosaur" characterized by a narrow pubis and what Welles called a
"long narrow femur" with a shape and form "quite different from
other plesiosaurs." However, Hector had figured the femur in edge-on view,
rather than face on, misleading Welles. Welles, along with D.R. Gregg,
redescribed the material after personal examination in 1971 (Records of the
Type Species: Mauisaurus haasti [HAHS-tie] Hector 1874 : for
Julius Haast (Sir Julius von Haast), who found the first specimens, and was also
the founder and first director of the
Megalneusaurus Knight 1898 "great swimming lizard"
(from Gr. megal- (megas) "great" + Gr. neus-
(neusis) "swimming" + Gr. sauros
"lizard") (m) named to indicate "the largest known animals of the
order Sauropterygia," with a forelimb and paddle originally (over)estimated
at 2.209 meters in length (1.5 meters may be more realistic); the largest known
plesiosaur prior to the discovery of Kronosaurus, and apparently similar
in size to giant specimens of Liopleurodon. Williston (1903) states that
"A large portion of the type species is known; the parts so far described
are the vertebrae and limbs." However, some of the original remains (ribs,
vertebrae) mentioned by Knight and Williston now would appear to be lost, since
the surviving specimen consists only of a fore-paddle, some vertebrae and
fragments of a pectoral girdle--material many researchers (but not all) have
considered inadequate to diagnose a genus and species. The relatively long and
slender humerus appears distinct in some details from the forelimbs of other
Jurassic pliosaurs. Recently Weems and Blodgett (U.S. Geological Survey Bulletin
2152: 169-175 (1996)) have identified parts of a plesiosaur humerus from the
Late Jurassic Naknek Formation of southern
Length: (estimated) ?10-14 m. (?34-46 ft.))
Type Species: Megalneusaurus rex [reks] (Knight 1895) "king," for its large size; for Cimoliosaurus rex Knight 1895. Pliosauroidea Late Jurassic (Kimmeridgian-Portlandian) NA.
Microcleidus Watson 1909 "small clavicle"
MIEK-ro-KLIE-duhs (Gr. mikros "small" + Gr. kleid- (kleis) "key, clavicle" + -us) (m) named for the small size of the clavicles: "The clavicular arch is reduced to thin sheets of bone adherent to the dorsal surface of the anterior rami of the scapulae. The interclavicle seems to have vanished completely" (Watson 1909); proposed for "Plesiosaurus" homalospondylus Owen 1865, founded on a nearly complete skeleton with a long neck (missing limb girdles) in the British Museum (BMNH 36184); Watson's description (1909) is based on a specimen in Manchester Museum (L. 7077, Manchester Museum), which included the limb girdles. The centra of the anterior neck vertebrae are relatively elongated; considered the earliest elasmosaurid by some researchers (Brown 1981).
Vertebrae: 39-40 cervicals / 5 pectorals / 17 dorsals / 3 sacrals /
Length: 6 m. (20 ft.); skull: .25 m. (10 in.)
Type Species: Microcleidus homalospondylus [HOM-a-lo-SPON-di- luhs] (Owen 1865) "even vertebrae": "for the even or level character of the terminal articular surfaces of the cervical vertebrae" (Owen 1865). (Holotype: BMNH 36184) Additional Species: Microcleidus macropterus [ma-KROP-ter-uhs] "large fin" (Seeley 1865); for "Plesiosaurus" macropterus Seeley 1865 ("the limbs are very large, and the hinder ones being slightly longer"). Watson (1911) transferred the species to Microcleidus because of similarities in the vertebrae and limb girdles, but considered the species distinct from M. homalospondylus based on differences in the limb structure.
NOTE: Bakker (1993) included the species Plesiosaurus brachypterygius
Huene 1923 in the genus Microcleidus as Microcleidus brachypterygius
(Heune 1923). However,
Morenosaurus Welles 1943 "
Vertebrae: 47 cervicals / 2 pectorals / 17 dorsals / 3 sacrals / 30
Length: (estimated) 8.3 m. (28 ft.))
Type Species: Morenosaurus stocki [STOK-ie] Welles 1943 (for Dr. Chester Stock, who collected the fossils). Plesiosauroidea Elasmosauridae Late Cretaceous (Maastrichtian) NA.
Morturneria Chatterjee & Creisler 1994 "for Mort Turner"
mor-tuhr-NEER-ee-uh (Mor(timer) + Turner + -ia) (f) named to honor Dr. Mort D. Turner, noted American geologist, for his support of the Seymour Island project in Antarctica, which recovered the type specimen (skull, vertebrae) (Holotype: TTU P 9219 (Texas Tech University)). (To replace preoccupied Turneria Chatterjee & Small 1989). Morturneria was a "trap" feeder with a broad skull, and upper and lower jaws lined with densely arranged small sharp teeth (38+ maxillary; 46+ dentary; 15 premaxillary), similar to Jurassic cryptoclidids and Aristonectes. The preserved cervical vertebrae are very unusual: the centra are short in length front-to-back (as in "pliosaurs"), broader than long or high (as in "cimoliasaurs"), with a strongly "binocular" shape, unlike the simple cylindrical shape of cervical vertebrae found in other known plesiosaurs (though Aristonectes has ovoid vertebrae toward the base of the neck). The articular ends are flattened: "platycoelous with distinctive lateral ridges." The classification is debated. N. Bardet (1995) has identified Morturneria and the apparently related (and larger) Aristonectes as elasmosaurids rather than cryptoclidids.
Length: skull: (estimated) 40 cm. (16 in.); mandible: 44 cm. (17.5 in.)
Type Species: Morturneria seymourensis [see-moh-REN-sis]
(Chatterjee & Small 1989) "from
Muraenosaurus Seeley 1874 "moray eel lizard"
(Muraena genus name for the moray eel (from Lat. muraena
(Gr. myraina) "sea eel")) + Gr. sauros
"lizard") (m) alluding to the reptile's long neck, suggesting a moray.
Muraenosaurus is known from complete skeletons and skulls from the lowest
deposits of the Oxford Clay,
Vertebrae: 43-44 cervicals / 3 pectorals / 19-20 dorsals / 4 sacral /
Length: 4.5-5.2 m. (15-21 ft.); skull: 40 cm. (16 in.)
Type Species: Muraenosaurus leedsii [LEED-zee-ie] Seeley
1874: for Charles E. Leeds, a British fossil collector, along with his brother
Alfred Leeds. C.E. Leeds showed Seeley the type specimen when Seeley visited
Additional Species: Muraenosaurus beloclis [BEL-o-klis] Seeley
1892 "arrow clavicle," for the pointed shape of the small
interclavicle. A small species, with an estimated adult size of about 2.5 m.
(8.4 ft.) long; made a separate genus (Picrocleidus) by Andrews in 1909.
Plesiosauroidea Elasmosauridae Late Jurassic (Callovian) Eur. (?
Occitanosaurus Bardet, Godefroit & Sciau 1999 "Occitanian lizard"
(Occitania + Gr. sauros "lizard") (m) named for
Occitania, the area in which the Occitan Romance language is spoken (currently
most of southern France, Val d'Aran of
Vertebrae: 43 cervicals / 3 pectorals / 16 dorsals / 4 sacrals / (?25
Length: estimated 4 m. (13.3 ft); skull: 25 cm (10 in.)
Type Species: Occitanosaurus tournemirensis [toor-nuh-meer-EN-sis]
(Sciau, Crochet & Mattei 1990: "from Tournemire," the town near
where the fossil was found in the Aveyron Department, southern
Ogmodirus Williston & Moodie 1913 "straight-line neck"
og-mo-DIE-ruhs (Gr. ogmos "straight line, furrow" + Gr. deire "neck" + -us) (m) named for the "short, uniform centra of the cervical vertebrae." Welles (1943: 193) suggested the specimen could be a juvenile Thalassomedon. Plesiosauroidea Elasmosauridae Late Cretaceous NA. [nomen dubium (?Thalassomedon)]
Oligosimus Leidy 1872 "small shortened (vertebra)"
OL-i-go-SIE-mus (Gr. oligos "little, few" + Gr. simos "depressed, concave, snub-nosed") (m) named for the shape of a small caudal vertebra: "The vertebra is from the base of the tail and is much shorter in relation to its other dimensions than in Plesiosaurus or Discosaurus." Plesiosauria i.s. Late Cretaceous NA. [nomen dubium]
Orophosaurus Cope 1887 "roofed lizard"
OR-o-fo-SAWR-uhs (Gr. orophe "roof" + Gr. sauros "lizard") (m) probably alluding to the coossified neural arches on the neck vertebrae, in contrast to Piptomerus, which had loose, unfused neural arches. Based on three vertebrae (caudals according to Welles). Plesiosauria i.s. Late Cretaceous NA [nomen dubium]
Pachycostasaurus Cruickshank, Martill & Noe 1996 "thick rib lizard"
(Gr. pakhys "thick" + Lat. costa "rib" + Gr. sauros
"lizard") (m) named to indicate a marine reptile with thickened dorsal
ribs and heavily ossified gastralia, in constrast to the lightly built bone
stucture found in most other known pliosaurids, which pursued prey near the
surface. Pachycostasaurus probably fed near the bottom on slower moving
prey such as anthropods, and may have been an estuarine or possibly a freshwater
form (similar bones have been identified in
Vertebrae: 13+ cervicals
Length: (estimated) 3.1 m. (10.3 ft.); skull (estimated): 63 cm. (25 in.))
Type Species: Pachycostasaurus dawni [DAW-nie] Cruickshank,
Martill & Noe 1996: "after Alan Dawn, discoverer of this new
animal" from the Peterborough Member, Oxford Clay Formation,
Pantosaurus Marsh 1893 "all lizard"
PAN-to-SAWR-uhs (Gr. pant- (pan) "all" + Gr. sauros "lizard") (m) replacement name for preoccupied Parasaurus Marsh; "The neck was long and slender. The vertebrae resemble most nearly in form and size those of Plesiosaurus plicatus Phillips." Plesiosauria i.s. Late Jurassic NA. [nomen dubium]
Parasaurus Marsh 1893 "near lizard"
PAYR-a-SAWR-uhs (Gr. para- "near" + Gr. sauros "lizard") (m) probably patterned after the name Plesiosaurus "near lizard"; for a fragmentary specimen of a small plesiosaur "the first Jurassic form observed in this country," consisting of a few strongly grooved vertebrae. (Preoccupied by Parasaurus Meyer. See Pantosaurus)
Peloneustes Lydekker 1889 "clay swimmer" ("Oxford Clay swimmer")
(Gr. pelos "clay, mud" + Gr. neustes
"swimmer") (m) alluding to the Oxford Clay in south central
Vertebrae: 21-22 cervicals / 5 pectorals / 20 dorsals / 3 sacrals /
Length: 3.1-4 m. (11-14 ft.); skull: 58 cm. (23.2 in.); mandible: 80 cm. (32 in.) )
Type Species: Peloneustes philarchus [fi-LAHR-kuhs] (Seeley
1869) "power-loving," probably alluding to its proportionately big
head and jaws, represented in the type specimen by part of the cranial rostrum
and a very long, nearly complete mandible. (Holotype: J.46913,
Pentatarsostinus Hawkins 1840 "five tarsal boned"
PEN-ta-tar-SOS-tin-uhs (Gr. penta "five" + Gr. tarsos "tarsus" + Gr. ostinos "bony") (m) referring to the construction of the paddle [= Plesiosaurus]
Peyerus Stromer 1935 "for Peyer"
(Peyer + -us) (m) named to honor Bernhard Peyer (1885--1963), noted Swiss
paleontologist, professor at Zurich, and friend of Stromer; for a specimen found
in the Sunday River marine or estuary beds at Uintenhage (Cape Province) South
Africa ("Plesiosaurus" capensis Andrews 1911). The form
appears to be quite similar to, if not congeneric with, the small freshwater or
estuarine Wealden pliosaurid Leptocleidus from
Vertebrae: 21-22 cervicals
Length: (estimated) 2.4 m. (9 ft.); skull: 27.7 cm. (11 in.))
Type species: Peyerus capensis [kay-PEN-sis] (Andrews 1911)
Picrocleidus Andrews 1909 "sharp-pointed clavicle"
PIK-ro-KLIE-dus (Gr. pikros "sharp-pointed" + Gr. kleid- (kleis) "key, clavicle" + -us) (m) named for the small arrow-shaped interclavicle and rudimentary clavicles in the front limb girdle; proposed for Seeley's Muraenosaurus beloclis ("arrow clavicle"); a rare small species. (estimated total length: 2.5 m. (8.3 ft.)). [= Muraenosaurus]
Piptomerus Cope 1887 "fall-out part (vertebrae)"
pip-TOM-e-ruhs (Gr. pipto "fall out" + Gr. meros "part, portion") (m) probably so-named because the various vertebrae have "neurapophyses and other processes articulating freely with the centra," an indication the specimens belonged to juveniles with unfused bones; based on various vertebrae that are not diagnostic. Plesiosauria i.s. Late Cretaceous NA. [nomen dubium]
Piratosaurus Leidy 1865 "pirate lizard"
pie-RAY-to-SAWR-uhs (Gr. peirates "pirate, robber" + Gr. sauros "lizard") (m) based on a single sharp-pointed tooth, originally attributed to a crocodilian. Plesiosauria i.s. Late Cretaceous NA. [nomen dubium]
Plesiopleurodon Carpenter 1996 "near-Liopleurodon"
PLEE-see-o-PLOOR-o-don (Gr. plesios "near" + (Lio)pleurodon (Gr. leios "smooth" + Gr. pleuron "side" + Gr. odon "tooth")) (m) named for its close resemblance to the Late Jurassic pliosaurid Liopleurodon; for a small pliosaur from the early Late Cretaceous (lowest Cenomanian) of North America (Belle Fourche Shale, Wyoming), known from a complete skull and lower jaw, plus some cervical vertebrae that are a little wider than long, and a coracoid. The mandible has a moderately long symphysis containing 8 pairs of large procumbent canine-shaped teeth; teeth circular in cross-section, with outer surface smooth except near the base, which is striated. The cervical vertebrae have single-headed ribs, as in other Cretaceous pliosauroids; the Late Jurassic Liopleurodon has double-headed cervical ribs.
Length: (estimated) 2.9 m. (9.2 ft.); skull: 71.2 cm. (2.3 ft.))
Type Species: Plesiopleurodon wellesi [WEL-zie] Carpenter 1996: for Samuel P. Welles (1909-1997), noted vertebrate paleontologist, for his lifelong work on plesiosaurs. (Holotype: CM 2815) Pliosauroidea Pliosauridae Late Cretaceous (Cenomanian) NA.
Plesiosauridae Gray 1825 "Plesiosaurus [near-lizard] family"
PLEE-see-o-SAWR-i-dee (masc. plural) Currently containing the single genus Plesiosaurus. On-going studies of early plesiosaurs could revise or expand the family with new genera.
Plesiosauroidea Welles 1943 "Plesiosaurus [near-lizard] super- family"
PLEE-see-o-saw-ROY-dee-uh (neuter plural) The group including plesiosaurs with relatively long necks (28-72 cervical vertebrae) and proportionately small skulls. The individual neck vertebrae are typically moderate to elongated in length, contrasting with the shorter, more compressed shape typical of "pliosaur" cervical vertebrae. Brown (1981) divided the Plesiosauroidea into the families Plesiosauridae, Elasmosauridae and Cryptoclididae. Ken Carpenter (1996) has included the Late Cretaceous Polycotylidae as a group of modified plesiosauroids related to elasmosaurids, but with short necks and relatively large, elongated skulls. (Currently, a range of other authors still classify the Polycotylidae as pliosauroids.) Some early forms such as Attenborosaurus combine long necks with relatively elongated pliosaur-like skulls, and may represent another distinct type of plesiosauroid, though as pointed out in Brown and Cruickshank (1994), on-going research into Early Jurassic plesiosaurs "is almost certain to overthrow the present superfamily and family divisions in the Plesiosauria." Persson (1960) recognized the family Cimoliasauridae for robust plesiosauroids that have necks intermediate in length with cervical vertebrae that are broader than long; until better material for the enigmatic and poorly known "cimoliasaurs" comes to light, however, most other researchers consider the group inadequately defined when based on such scrappy material. The Late Cretaceous plesiosauroids Aristonectes and Morturneria have a dense arrangement of small, thin teeth in their jaws and thus resemble cryptoclidids, though some authors have classified them as elasmosaurs, or even "cimoliasaurs."
Members: Plesiosauridae, Elasmosauridae, Cryptoclididae, Polycotylidae; Attenborosaurus,
Thalassiodracon, Sthenarosaurus, "Plesiosaurus" macrocephalus
(to be redescribed by Brown and
Plesiosaurus De la Beche & Conybeare 1821 "near lizard" ("approximate to the Saurians"*)
(Gr. plesios "near to, approaching" + Gr. sauros
"lizard" + -us)* (m) a name "expressing its near approach
to the order Lacerta." As explained by
Plesiosaurus is distinguished from other genera by the small size of its head, as well as by the relative shortness of its skull in front of the orbit and in the temporal region. The snout is fairly broad and has a pointed tip. The pineal opening is large. The teeth are uniform in shape: long, slender, pointed, round in cross-section, with vertical striations but no carinae. The internal nostrils on the palate are placed almost directly under the external nostrils, and so do not appear to be designed for underwater olfaction, unlike in plesiosaurs such as Cryptoclidus and Rhomalaeosaurus that have the internal nares shifted forward, apparently to allow water to pass through the roof of the mouth and up and out the animal's nose as it swam.
The genus Plesiosaurus has a long and complex taxonomic history,
complicated by use of the name as a "wastebasket" genus for various
scrappy finds--most proposed species of Plesiosaurus from outside
In the most recent review of Plesiosaurus, Glenn Storrs (1997, in
Ancient Marine Reptiles:145-190) only recognizes two currently definable
species: (1) the type species Plesiosaurus dolichodeirus from the
Sinemurian (Lower Lias) of Britain; and (2) Plesiosaurus guilelmiimperatoris
from the later Toarcian (Upper Lias) of Southern Germany, distinguished by
"a more delicate skull and a more robust, straighter humerus" than in P.
A number of Jurassic species originally classified in Plesiosaurus and based on good type material have been redescribed as new genera: Archaeonectrus, Attenborosaurus, Eretmosaurus, Eurycleidus, Microcleidus, Peloneustes, Rhomaleosaurus, Thalassiodracon. "Plesiosaurus" propinquus (sometimes classified as a species of Rhomaleosaurus) and "Plesiosaurus" longirostris (currently classified as a species of Macroplata) may also be revised as new genera. Dave Brown and Glenn Storrs are currently revising the species "Plesiosaurus" macrocephalus "large-headed" Conybeare in Buckland 1836 (Type: BMNH R1336) (synonym: "Plesiosaurus" brachycephalus Owen 1840) from the Lias (Sinemurian) of England; known from nearly complete skeletons (up to 3.2 m. (10.5 ft.) long) that combine a neck consisting of 29-30 relatively long, plesiosaurid-type vertebrae with a comparatively large, broad triangular skull ending in an elongated blunt snout, the neck being about twice as long as the head. A specimen of "Plesiosaurus" macrocephalus in the Manchester Museum preserves "the apparent remains of the skin indicating the former existence of a posterior extension of the fin unsupported by bone" (Watson 1911); this soft-tissue outline appears less extensive than the controversial impression around the right forefin of the type specimen of Plesiosaurus guilelmiimperatoris (see comments below).
The derivation of the name Plesiosaurus continues to cause confusion. Some recent books indicate incorrectly that Plesiosaurus means "ribbon lizard," supposedly for the ribbon- like appearance of the neural spines along its backbone. There is NO basis in Greek or Latin for such a reading--nor in Conybeare's own comments! Conybeare originally proposed the name based on incomplete material (vertebrae, paddles, ribs) that permitted only an imperfect notion of what the entire animal looked like. Mary Anning's discovery in 1823 of a nearly complete specimen (BMNH 22656, now the holotype) prompted Conybeare to revise his thinking about his choice of name. He stated in 1824 that: "The name I have originally given to this animal, Plesiosaurus (approximate to the Saurians), may appear rather vague in this stage of our knowledge, and an appellation derived from its peculiar length of neck might be preferred; but for the present I shall retain the old generic name, adding for specific distinction the well-known Homeric epithet Dolichodeirus ["long- necked"], as characterizing the most striking peculiarity of its osteology." The derivation of Plesiosaurus is now typically simplified to "near lizard" (a noun), though Conybeare (1824) explained that he formed the name as a substantivized adjective by analogy with classical Greek adjectives such as isodendros (isos "equal to" + dendron "tree" + -os) "tree-like"--some of Conybeare's Greek-savvy colleagues originally objected to the proposed name Plesiosaurus on philological grounds.
Vertebrae: 37-42 cervicals / 4-5 pectorals / 21 dorsals / 3 sacrals /
Length: up to 3.5 m. (12 ft.); skull: 16-19 cm. (6.3-7.8 in.); mandible: 21-24 cm. (9-10.5 in.)
Type Species: Plesiosaurus dolichodeirus [DOL-ik-o-DIE-ruhs] Conybeare 1824 "long-necked" Holotype: BMNH 22656. Known from a number of complete specimens. (Synonyms: Plesiosaurus macromus Owen 1840.)
Additional Species: Plesiosaurus guilelmiimperatoris [gwi-LEL-
mie-IM-per-ay-TOH-ris] Dames 1895: "of Emperor Wilhelm"--to honor
Kaiser Wilhelm II, Emperor of Germany, (1859-1941), who authorized funds for the
purchase of the specimen for the
Pliosauridae Seeley 1874 "Pliosaurus [near-saurian] family"
PLIE-o-SAWR-i-dee (masc. plural) Many authors use the family Pliosauridae as a synonym of the superfamily Pliosauroidea, to embrace all short-necked plesiosaurs. If the "classic" large pliosauroids of the Middle Jurassic through early Late Cretaceous are separated out, the Pliosauridae might be used in a more restricted sense to include advanced pliosauroids with necks containing 17 to 20 vertebrae; advanced pliosauroids with necks containing only 12 to 13 vertebrae are sometimes separated out as the Brachaucheniidae. Early short-necked plesiosaurs such as Rhomaleosaurus and Macroplata, often included in the Pliosauridae, may be a distinct group but more study is needed (Hampe 1992; Gasparini 1997). For purposes of this guide, Pliosauridae is used only for genera that appear more closely related to Pliosaurus than to Rhomaleosaurus. The superfamily Pliosauroidea is used in this guide for other short-necked forms that might be reclassified in the future. See additional comments under Pliosauroidea.
Members: Pliosaurus (type), Peloneustes, Liopleurodon, Plesiopleurodon, Polyptychodon, ?Simolestes, (?Maresaurus)
Pliosauroidea Welles 1943 "Pliosaurus [near-saurian] super- family"
PLIE-o-saw-ROY-dee-uh (neuter plural) Many authors have grouped all plesiosaurs with short necks and proportionately large heads in the single family Pliosauridae, making it synonymous with the superfamily Pliosauroidea. Recent analyses indicate that the real evolutionary picture may be more complex, and that the short-necked "pliosaur" body-plan may have evolved more than once in different groups of plesiosaurs. Taylor and Cruickshank (1993) characterize pliosauroids as "markedly more plesiomorphic than plesiosauroids," with skulls "retaining lacrimals, prefrontals, prearticulars, and coronoids, all presumably present in the common ancestor of plesiosaurs and lost in plesiosauroids." Brown and Cruickshank (1994) cite features of the cheek structure for separating the Pliosauroidea (Pliosauridae) as the sister group of the Plesiosauroidea, but caution that "an ongoing review of Lower Jurassic genera involving several workers...is almost certain to overthrow the present superfamily and family divisions in the Plesiosauria."
At present, no broad consensus exists about how to reclassify all the proposed members of the catch-all version of the family Pliosauridae. In the very strictest sense, the Pliosauridae proper could include the long-snouted Late Jurassic Pliosaurus, Peloneustes, Liopleurodon (and probably the short-snouted Simolestes), plus the long-snouted Cretaceous Plesiopleurodon and Polyptychodon. Recently published research shows that the distinction between "pliosauroid" and "plesiosauroid" is much more difficult to characterize for very early plesiosaurians (Cruickshank, 1997)--a short or a long neck may not be automatically diagnostic. Some authors have referred forms with shortened skulls and spoon-shaped snouts (Rhomaleosaurus, Macroplata, etc.) to the family Rhomaleosauridae, but the spatulate symphysis may be a convergent character resulting from similar feeding habits (bite, twist and tear), and a new analysis appears needed (Hampe 1992; Gasparini 1997). A few authors (Hampe 1992; Carpenter 1996) have used the family Brachaucheniidae for Brachauchenius and Kronosaurus, based in part on the animals' extremely short necks compared to other pliosauroids. The clearest case for separate family status has been made for the Polycotylidae, which Carpenter (1996, 1997) classifies as a family of short-necked plesiosauroids, and thus not "pliosaurs" at all; for now, a range of other researchers still treat polycotylids as true pliosauroids. White (1940) proposed the family Leptocleididae for Leptocleidus, Rhomaleosaurus and Eurycleidus, based on features of the limb girdles that are no longer considered of major diagnostic importance.
Members: Pliosaurus (type); Liopleurodon, Peloneustes, Plesiopleurodon, Polyptychodon; Simolestes, Maresaurus; Megalneusaurus; Strongylokrotaphus; Archaeonectrus, Bishanopliosaurus, Eurycleidus, Macroplata, Rhomaleosaurus, Yuzhoupliosaurus; Leptocleidus; Pachycostasaurus; Brachauchenius, Kronosaurus Undescribed Members: the "Richmond pliosaur" from Australia and the Adams Museum pliosaur from South Dakota appear to be primitive polycotylids.
Pliosaurus Owen 1841 "more saurian"
PLIE-o-SAWR-uhs (Gr. pleion "more" + Gr. sauros "lizard") (m) named to indicate a reptile that was supposedly even more like a crocodile in its anatomical organization than Plesiosaurus was according to the chain-of-being-type classification still widely accepted in England in the 1840s. In Owen's words (1842), "The Enaliosaurs are immediately connected with the Crocodilian reptiles by an extinct genus, represented by species of gigantic size...The Reptile in question is essentially a modified Plesiosaurus, but its modifications appear to entitle it to be regarded as a distinct genus, which, as it is more closely allied to the true Sauria, I have proposed to call Pliosaurus." Owen (1841) cited the "more crocodilian proportion of the teeth" in particular. The genus is now known from a number of complete skulls and lower jaws, and partial skeletons.
Some authors do not recognize a distinction between Pliosaurus and Liopleurodon. Tarlo (1960) argued that the two genera should be separated based on their skulls and teeth. Pliosaurus has a long, relatively deep skull that narrows into an extended blunt snout in front of the nostrils. The lower jaw (mandible) has a long joined tip (symphysis), bearing 10-12 pairs of teeth, the first 5-6 being large and canine-shaped. There are 30-38 teeth in each branch of the jaws. The teeth are trihedral (three-sided) in cross-section, in contrast to the typically conical teeth of Liopleurodon.
Vertebrae: 20 cervicals
Length: (estimated) 10-12 m. (33-40 ft.); skull: 1.5-2 m. (5-6.6 ft.)
Type Species: Pliosaurus brachydeirus [brak-ee-DIE-ruhs]
"short- necked" Owen 1841; "the vertebrae of the neck are so
modified that the peculiarly elongated proportion of this part of the spine,
which characterizes the typical Pleisosauri, is exchanged for one that much more
nearly approaches the oppposite condition of the cervical region in the
Ichthyosauri" (Owen 1841). (Holotype: J.9245 A, B;
Additional species: Pliosaurus brachyspondylus [brak-ee-SPON-dil- uhs] (Owen 1839) "short vertebra". "The most striking peculiarity of this species is that the anterior cervical vertebrae are even more compressed in the antero-posterior direction than the posterior cervical vertebra...hence we may conclude that the neck was shorter in the Pl. brachyspondylus than in the other Plesiosauri, and it may be inferred that it had a large and heavy head." (Owen 1840) Tarlo distinguished this species based in part on the centra of the neck vertebrae, which have a strip of finely sculptured rugose bone in a ring near each end, with a smooth area in-between.
Pliosaurus andrewsi [AN-droo-zie] Tarlo 1960: for Charles William Andrews (1866-1924), British paleontologist; a large form from the Oxford Clay (Callovian); teeth circular in cross-section; possibly a large form of Peloneustes (Martill 1991).
NOTE: Pliosaurus macromerus [mak-ro-MEER-uhs] "long femur"
Phillips 1871. Tarlo (1959) created a new genus Stretosaurus for Pliosaurus
macromerus Phillips 1871, based on the supposedly unusual form of the
scapula. Halstead [= Tarlo] (1989) reidentified the "scapula" as an
ilium after a more complete specimen was found, and transferred the species to Liopleurodon.
However, Tarlo's 1960 definition mentions teeth that are trihedral in
cross-section, a feature more characteristic of Pliosaurus. Hampe (1992)
disputed Halstead's (1989) placement of this species in the genus Liopleurodon,
and restored it to Pliosaurus. The species is also identified from
Polycotylidae Cope 1869 "Polycotylus [deep-cup] family"
POL-ee-ko-TIL-i-dee (masc. plural) Polycotylids share a set of distinctive features that set them apart from other short-necked plesiosaurs, including a relatively long neck (19-26 vertebrae) with single-headed ribs, short and wide propodials (humerus and femur) and a skull with large orbits, a high sagittal crest, and a very narrow, elongated snout. The jaws have relatively small, uniform conical teeth and lack the powerful canine teeth found at the tip of the snout in other "pliosaurs." Polycotylid skulls show a strong superficial resemblance to those of ichthyosaurs. Since polycotylids are known primarily from the Late Cretaceous after the extinction of ichthyosaurs, they appear to have replaced the "fish lizards" as fast-swimming marine predators that preyed on cephalopods and small fish. Preserved stomach contents include ammonite beak parts.
Traditionally, these small short-necked, large-headed plesiosaurs have been
considered "pliosaurs," and classified either in the family
Pliosauridae itself or as a distinct family (Polycotylidae) in the superfamily
Pliosauroidea. New research questions this assumption. Ken Carpenter (1996,
1997) interprets polycotylids as a group of short-neck plesiosauroids, closely
related to elasmosaurids based on common features in the skull; Nathalie Bardet
(1998) has supported this reclassification. By contrast, Robert Bakker (1993)
has argued that polycotylids are true pliosauroids and that long-necked
Cretaceous elasmosaurs such as Brancasaurus, etc., evolved not from
long-necked Jurassic plesiosauroids but from small pliosauroids that were
ancestral to Leptocleidus and polycotylids. Important new evidence may
help trace the origin of polycotylids--the "
Currently, polycotylids are best known from partial and complete skeletons
and skulls discovered in Late Cretaceous marine beds in
Synonyms: Dolichorhynchopidae Welles 1962, Trinacromeridae Novozhilov 1964 (ex Trinacromerinae Nopsca 1923)
Members: Polycotylus (type), Trinacromerum, Dolichorhynchops,
Georgiasaurus Undescribed Members: "
Polycotylus Cope 1869 "deep cup (vertebrae)"
(Gr. polys "much, many, very" + Gr. kotyle
"cup" + -us) (m) named for "deeply biconcave
vertebrae"; Cope lists: "Depth of cup of vertebrae .63 Inches."
Cope's type material (USNM 27678) was scrappy and the genus now is based mainly
on a Yale specimen (YPM 1125) collected by O.C. Marsh and briefly described by
Williston in 1906. The concave vertebrae appear to be diagnostic. With a neck
longer than in Dolichorhynchops and Trinacromerum, differing also
in the placement of tail chevrons and a posteriorly curved ilium. The teeth are
robust with coarse striations. Schumacher & Martin 1995 attribute a nearly
complete skeleton from
Vertebrae: 26 cervicals / 3 pectorals / 25 dorsals / 2-3 sacrals / ?25
Length: (estimated) 5 m. (17 ft.); skull: 94 cm. (3 ft.); mandible: 98 cm. (3.1 ft.)
Type Species: Polycotylus latipinnus [lat-i-PIN-uhs] Cope 1869 "broad fin": "from the great relative stoutness of the paddle" based on a rather poorly preserved podial bones. Plesiosauroidea Polycotylidae Late Cretaceous (Santonian) NA.
Polyptychodon Owen 1841 "many ridged tooth"*
(Gr. polys "much, many" + Gr. ptykhos "fold,
wrinkle, ridge" + Gr. odon "tooth") (m) named for
large conical striated teeth: "the longitudinal ridges of the enamel are
set close all round the crown, whence the name of the genus." Polyptychodon
has had a confusing history until recently, and was known at first only from
teeth. Owen (1840, 1841) was unsure if the characteristic teeth belonged to a
kind of crocodile, a plesiosaur, or to another, unknown type of reptile. He
later attributed large bones found at
Polyptychodon is of particular interest since it represents survival
into the early Late Cretaceous (Cenomanian-Turonian) of the conical-toothed line
of giant pliosaurids that flourished in the Late Jurassic and Early Cretaceous.
Possible Polyptychodon material has also been found in
Length: (P. interruptus) (estimated) 10-11 meters (33-35 ft.); skull: (estimated) 170 cm. (5.6 ft.); mandible (estimated): 195 cm. (6.5 ft.)
Type Species: Polyptychodon interruptus [in-ter-RUP-tuhs] Owen 1851 "interrupted (enamel)"; for large conical teeth on which the "enamelled striated coat terminates by an abrupt and well-defined border."
Additional species: Polyptychodon hudsoni [HUHD-so-nie] Welles & Slaughter 1963 (for V.L. Hudson, Jr., who collected the type specimen) Pliosauroidea Pliosauridae Late Cretaceous (Cenomanian-Turonian) Eur., NA., ?EEur. [corrected 7/2000]
Rhomaleosauridae Kuhn 1961 (ex Rhomaleosaurinae Nopsca 1928) "Rhomaleosaurus [robust-lizard] family"
roh-MAY-lee-o-SAWR-i-dee (masc. plural) Proposed for short-necked plesiosaurs with spoon-shaped snouts. "Rhomaleosaurids" have relatively large skulls (about 1/8th to 1/6th the total length of the body) with comparatively short snouts ending in an expanded tip equipped with large canine-type teeth, a feature likely used to tear off flesh by biting, then twisting the entire body the way modern crocodiles do. The fairly inflexible neck was about 1.5 to 2 times the length of the skull and made up of short, compact centra. Similarities in the shape of the skull of proposed "rhomaleosaurids" such as Rhomaleosaurus, Macroplata, Simolestes and Leptocleidus may be the result of convergence because of similar diets and hunting techniques rather than a feature that defines a group of plesiosaurs that are closely related by evolutionary history through a common ancestor. As a result, most current scholars do not recognize the Rhomaleosauridae has a phylogenetically based group, though the term "rhomaleosaurid" sometimes is used informally to indicate plesiosaurs with a particular body and skull design.
Rhomaleosaurus Seeley 1874 "robust lizard"
roh-MAY-lee-o-SAWR-uhs (Gr. rhomaleos "strong, robust" + Gr. sauros "lizard") (m) referring to the robust trunk and limbs typical of plesiosaurs; originally proposed for "Plesiosaurus" cramptoni Carte & Bailey 1863 (Holotype: NMING F8785). Rhomaleosaurus is known from complete skeletons and skulls, and typifies a distinct group of short-necked plesiosaurs sometimes placed in the separate family Rhomaleosauridae (see Rhomaleosauridae). Rhomaleosaurus itself has a subtriangular skull about 15% of its overall length, with 30 circular-in-cross- section teeth in each ramus of the lower jaw. The skull has a short snouts ending in an expanded tip equipped with large canine-type teeth, a feature likely used to tear off flesh by biting, then twisting the entire body the way modern crocodiles do. The fairly inflexible neck is composed of about 28 short, rather compact vertebrae, and is about 1.5 times the length of the skull.
Research by Cruickshank, Small and
The genus has a complex taxonomic and nomenclatural history. Seeley proposed the name Rhomaleosaurus for "Plesiosaurus" cramptoni Carte & Baily 1863. Cruickshank (1996) synonymized the species Rhomaleosaurus cramptoni with the earlier name "Plesiosaurus" zetlandicus Phillips 1854, making Rhomaleosaurus zetlandicus the type species; Cruickshank (1996) also made the species Rhomaleosaurus thorntoni Andrews 1922 a junior synonym of the type species. Currently a number of other distinct species are included in the genus by many researchers, including (1) the 5 m. (16.3 ft.) long "Plesiosaurus" megacephalus Stutchbury 1846, which has a longer snout and different dentition from Rhomalesoaurus zetlandicus, and (2) the 3.44 m. (11.5 ft.) long "Thaumatosaurus" victor Fraas 1910, from southern Germany, which has much larger paddles, a smaller skull and a proportionately longer neck than other species. "Plesiosaurus" propinquus Tate & Blake 1876 is sometimes included in Rhomaleosaurus, but additional study may justify making it a new genus.
Older sources (including Romer 1956) commonly used the name Thaumatosaurus for the genus now called Rhomaleosaurus. The generic name Thaumatosaurus was originally proposed by von Meyer in 1841 based on fragmentary plesiosaur material that cannot be diagnosed in a scientifically useful way. Perhaps motivated by personal animosity toward H. G. Seeley, Richard Lydekker (1889) nonetheless used von Meyer's older name Thaumatosaurus in place of Seeley's Rhomaleosaurus for the British shortnecked species "Plesiosaurus" cramptoni, zetlandicus and propinquus. Eberhard Fraas (1910) also used the name Thaumatosaurus for his new species Thaumatosaurus victor from the Lias of Germany. In 1960, Tarlo rejected use of Thaumatosaurus because of the indeterminate nature of von Meyer's type specimen and restored Seeley's Rhomaleosaurus as the valid name, a usage now accepted by nearly all researchers.
Vertebrae: 25-32 cervicals / 4 pectorals / 26 dorsals / 4 sacrals /
Length: 3.3-7 m. (11-23 ft.); skull: 1.1+ m. (3.3+ ft.)
Type Species: Romaleosaurus zetlandicus [zet-LAND-i-kus]
(Phillips 1854) "from Zetland (
Additional species: Rhomaleosaurus megacephalus [meg-a-SEF-a-lus]
(Stutchbury 1846) "big-headed"; earlier (Hettangian) than Rhomaleosaurus
zetlandicus, with a more gracile skull; the type specimen (Plesiosaurus
megacephalus Stutchbury 1846) in the
Rhomaleosaurus victor [VIK-tor] (E. Fraas 1910) "conqueror,"
named to characterize the excellent type specimen ("surpassing in beauty
all previous discoveries") and for Viktor Fraas (brother of Eberhart Fraas),
who helped secure the fossil for the
Rhomaleosaurus propinquus [pro-PING-kwuhs] (Blake 1876) "near"; the lower jaw is different from that of other species of Rhomaleosaurus, and may justify reclassification as a new genus after additional study. Pliosauroidea Early Jurassic (Hettangian-Toarcian) Eur.
Scanisaurus Persson 1959 "Scania (
(Scania, a province of southern Sweden + Gr. sauros
"lizard") (m) named to indicate a form found in the province of Scania,
in the Baltic region of southern Sweden; for Cimoliasaurus nazarowi
Bogolubov 1911, based on a posterior cervical vertebra that is very short and
broad, found on the banks of the Volga River in Chkalov oblast, Russia. Persson
(1959) attributed additional fragmentary material (striated teeth, limb
material, vertebrae) from Scania in
Seeleyosaurus White 1940 "Seeley's lizard"
(Seeley + Gr. sauros "lizard") (m) named to honor Harry
Govier Seeley (1839-1909), British vertebrate paleontologist: "who laid the
foundation for our understanding of the Plesiosauria." Proposed for a
specimen (SMNS 12039) from the Holzmaden of southern
Type Species: Seeleyosaurus holzmadensis [holtz-ma-DEN-sis]
White 1940 "from Holzmaden (
Simolestes Andrews 1909 "snub-nosed robber"
(Gr. simos "snub-nosed" + Gr. lestes
"robber") (m) named for the shape of the skull: "the head is
short and broad, the snout not being elongated as in Pliosaurus and Peloneustes."
Type species is known from a nearly complete skeleton with skull (BMNH R.3319)
and a smaller juvenile (BMNH R.3170); additional material has been found in
Vertebrae: 20 cervicals / 30-32 dorsals /18+ caudals
Length: (estimated) 6 m. (20 ft.); skull: 73 cm. (2.7 ft.)); mandible 97 cm. (3.2 ft.))
Type Species: Simolestes vorax [VOR-aks] Andrews 1909 "voracious" after its large teeth (Callovian of Europe)
Additional Species: Simolestes indicus [IN-di-kus]
(Lydekker 1877) "from
Simolestes keileni Godefroit 1994, based on a fragmentary skeleton
from the Upper Bajocian from
NOTE: According to Bardet & Hua (1996), the supposed African species
"Simolestes" nowackianus is based on part of a jaw
belonging to the teleosaurid crocodile Machimosaurus. Pliosauroidea
?Pliosauridae Late Jurassic (Bajocian-Tithonian)
Sinopliosaurus Young 1944 "Chinese pliosaur"
(New Lat. sino- (Gr. Sinai (Lat. Sinae))
"Chinese" + Pliosaurus (Gr. pleion
"more" + Gr. sauros "lizard")) (m) named to
indicate a pliosaur from Weiyuan,
Spondylosaurus Fischer 1845 "vertebra lizard"
SPON-di-lo-SAWR-uhs (Gr. spondylos "vertebra" + Gr. sauros "lizard")) (m) a form based on an isolated fossil vertebra (anterior cervical centrum) from Kimmeridge Clay of the Moscow Basin, Russia [= Pliosaurus]
Sthenarosaurus Watson 1909 "strong lizard"
STHEN-a-ro-SAWR-uhs (Gr. sthenaros "strong" + Gr. sauros "lizard")) (m) named to indicate a robustly built plesiosaur, known from an incomplete skeleton, lacking a skull. The coracoids are "short and thick," while the pelvis is "remarkably broad and sturdy"; the dorsal vertebrae have very short centra, but are very broad and high, with thick slanting neural spines. The 18 preserved neck vertebrae differ greatly in size so that the largest is nearly twice the depth, width and length of the smallest. If the entire neck was only somewhat more than 18 vertebrae long, it would be more strongly tapered for its length than in other known plesiosaur. Sthenarosaurus shares some features of the scapulae and coracoids, propodials and neck vertebrae with early short-necked forms such as Archaeonectrus, though its individual neck vertebrae are proportionately longer. It may represent a distinct category of plesiosauroid, and is currently classified as Plesiosauroidea incertae sedis (uncertain placement).
Vertebrae: 18+ cervicals
Length: (estimated) 2.8-3 m. (9-10 ft.)
Type Species: Sthenarosaurus dawkinsi [DAW-kin-zie]
Watson 1909: "for Prof. William Boyd Dawkins". (Holotype:
Streptosauria Cope 1869 "reversed lizards"
(Gr. streptos "turned, reversed" + Gr. sauros
"lizard" + -ia) (neuter plural) Following one of the most
notorius blunders in the history of vertebrate paleontology, E. D. Cope proposed
the name Streptosauria for "a group of high rank among the Reptiles, which
is allied to the Sauropterygia," diagnosed based on the "articular
processes of the vertebrae" which were "reversed in their direction,
viz., the anterior looking downwards, the posterior upwards." Cope
explained: "The characters of the order are altogether peculiar. They are
largely derived from an almost complete specimen of Elasmosaurus platyurus
Cope in the Museum of the
Stretosaurus Tarlo 1959 "Stretham (
(Stret(ham) + Gr. sauros "lizard") (m) named for
Stretham, near where the fossil was found in the Kimmeridge Clay of
Strongylokrotaphus Novozhilov 1964 "rounded temples"
STRON-jil-o-KROT-a-fuhs (Gr. stroggylos "round" + Gr. krotaphos "temple (of the head)") (m) alluding to the large "semicircular" temporal openings in the skull; for "Peloneustes" irgisensis Novozhilov 1948, found near the town of Pugachev, in the Saratov Oblast, Moscow Basin, Russia. Based on an incomplete skull, preserving the back of the skull up to the orbits and the pointed tip of the snout with "skull comparatively short, for which the length exceeds the width not more than twice"; a long, narrow paddle is also attributed to the genus. Novozhilov (1964) classified Strongylokrotaphus as a member of the "Trinacromeridae," though Tarlo (1960) thought the specimen was closely related to Pliosaurus; a revision of the taxon is needed.
Length: (estimated) 5-6 m. (17-20 ft.); skull: (estimated) 95 cm. (3.2 ft.))
Type Species: Strongylokrotaphus irgisensis [eer-gee-SEN-sis]
(Novozhilov 1948): "from the
Styxosaurus Welles 1943 "Hell Creek (
STIK-so-SAWR-uhs (Styx, mythical river in Hades + Gr. sauros "lizard") (m) alluding to the type locality at Hell Creek, Logan County, Kansas; proposed for "Cimoliasaurus" snowii Williston 1890, based on a skull and anterior neck vertebrae from the Niobrara (Holotype: KUMNH 1301). Carpenter (1999: Paludicola 2(2)) revised Styxosaurus snowii, confirming its status as a distinct and diagnosable taxon (contrary to Welles 1962); Carpenter also included material previously classified as species of Alzadasaurus (A. pembertoni (based on a nearly complete skeleton (SDSM 451)) and A. kansasensis) as junior synonyms of Styxosaurus snowii, but made the proposed second species "Styxosaurus browni" Welles 1952 a junior synonym of Hydralmosaurus serpentinus. Styxosaurus as redefined has 62 neck vertebrae, external nares positioned over maxillary tooth 6-7, and a long and low atlas-axis centrum.
Vertebrae: 62 cervicals / 3 pectorals / 19 dorsals / 4 sacrals /
Length: 9+ m. (30+ ft.); skull: 42 cm. (21 in.)
Type Species: Styxosaurus snowii [SNOH-ee-ie] (Williston 1890):
for Francis Huntington Snow (1840-1908), naturalist at the
Sulcusuchus Gasparini & Spalletti 1990 "furrow (jaw) crocodile"
suhl-kuh-SOOK-uhs (Lat. sulcus "furrow" + Gr. soukhos "crocodile") (m) named for the deep furrows along the outerside of the rostrum of a supposed dyrosaurid crocodile: additional research and new fossil material have shown that the taxon is a late-surviving polycotylid plesiosaur instead (Gasparini & de la Fuente, 2000). Sulcusuchus is known from a fragment of a rostrum (Holotype: MLP 88-IV-10-1 (Museo de la Plata)) found in the Late Cretaceous (early-middle Maastrichtian) Coli Toro Formation near Jacobacci, Rio Negro Province, Argentina; plus a partial skull and mandible (MPEF 650 (Museo Paleontologico 'Eigidio Feruglio,' Chubut)) found in the Late Cretaceous (late Campanian-early Maastrichtian) La Colonia Formation at Cerro Bosta, Chubut Province, Argentina. Sulcusuchus is an extremely longirostrine (long-snouted) polycotylid, with deep furrows on the outer side of the upper and lower jaws (maxilla and dentary), and pterygoids fused to form a plate; it was probably similar in size to Dolichorhynchops (around 3-4 m (10-13 ft) long), but more derived, with a longer snout and shorter spaces between the alveoli for its teeth.
Type Species: Sulcusuchus erraini [e-RIE-nie] Gasparini & Spalletti 1990: "for Errain" Plesiosauroidea Polycotylidae Late Cretaceous (Maastrichtian) SA [added 6-2002]
Taphrosaurus Cope 1870 "pit (vertebra) lizard"
TAF-ro-SAWR-uhs (Gr. taphros "pit, trench" + Gr. sauros "lizard")) (m) referring to the vertebrae: "the sutural attachment [of the centrum and arch] is the surface of a sub-round pit..." Pliosauroidea Late Cretaceous NA. [nomen dubium]
Thalassiodracon Storrs & Taylor 1996 "sea dragon"
(Gr. thalassa "sea" + Gr. drakon
"dragon")* (m) a name "alluding to the colloquial designation
['sea dragon'] given the Street marine reptile fauna found by [Thomas]
Length: 1.5-2 m. (5-6.5 ft); skull: 17-20 cm. (7-8.2 in.); mandible: (estimated) 21-26 cm. (8.2-10.3 in.)
Type Species: Thalassiodracon hawkinsi [HAW-kin-zie] (named to
honor Thomas Hawkins (1810-1889), English fossil collector "as a sincerely
offered though inadequate tribute of admiration of the indefatigable labour and
rare skill with which its remains have been disencumbered of their earthy
shroud" (Owen 1840)). Seeley respelled Owen's species name Plesiosaurus
hawkinsi, although under the International Code of Zoological Nomenclature
(Art. 31) Owen's original spelling hawkinsii should have been preserved.
Under the Fourth Edition of the ICZN (effective in 2000),
Thalassiosaurus Welles 1943 "marine lizard"
tha-LAS-ee-o-SAWR-uhs (Gr. thalassios "belonging to the sea" + Gr. sauros "lizard") (m) named to indicate a sea-going reptile; for Polycotylus ischiadicus Williston 1903, based on a juvenile specimen. Welles (1952) attributed additional material but (1962) transferred the species to Elasmosaurus, judging the material undiagnostic.
Vertebrae: 38+ cervicals / 3-4 pectorals / 15-20 dorsals / 3-6 sacrals / 30 caudals
Type species: Thalassiosaurus ischiadicus [ish-ee-AD-i-kus] (Williston 1903) "sciatic," in reference to the ischia, which differ from those in Dolichorhynchops. Plesiosauroidea Elasmosauridae Late Cretaceous NA. [nomen dubium]
Thalassomedon Welles 1943 "sea lord" or "lord of the sea"*
or tha-LAS-o-MEE-don (Gr. thalassa "sea" + Gr. medon
"lord, ruler") (m) named to indicate a giant sea-going elasmosaur;
based on a complete skeleton with skull (Holotype: DMNH 1588) found in the
Graneros Shale (Lower Cenomanian) in
Vertebrae: 62 cervicals / 3 pectorals / 25 dorsals / 3 sacrals / 21
Length: 12 m (40 ft.); skull: 47 cm. (18.7 in.)
Type Species: Thalassomedon haningtoni [han-ing-TOE-nie] Welles 1943: for Charles H. Hanington, president of the Colorado Museum of Natural History. (Holotype: DMNH 1588) (Synonyms: Alzadasaurus riggsi).
Thalassonomosaurus Welles 1943 "sea-living lizard"
THAL-a-SON-o-mo-SAWR-uhs (Gr. thalassonomos "living in or deriving nourishment from the sea" + Gr. sauros "lizard")* (m) named to indicate a sea-going reptile; for "Elasmosaurus" marshi Williston 1906. A juvenile specimen "too distinct to be included in any known genera" based on its scapulae and humerus. Plesiosauroidea Elasmosauridae Late Cretaceous NA. [nomen dubium]
Thaumatosaurus von Meyer 1841 "wonder lizard"
(Gr. thaumato- (thauma) "wonder" + Gr. sauros
"lizard") (m) named for its large size. Von Meyer characterized Thaumatosaurus
as an animal of the colossal size of a dinosaur, but with solid limb bones,
indicating a swimming form. The rough appearance of a jaw bone fragment
suggested an armored animal, and von Meyer originally proposed that his saurian
was related to crocodiles. However, in a later, more detailed description
(1856), he concluded correctly that Thaumatosaurus was related to Pliosaurus.
The type material consists of fragments of teeth, jaws, ribs, and vertebrae from
the Oxfordian of Wuerttemberg in
Tremamesacleis White 1940 "perforated interclavicle"
trem-a-MES-a-klies (Gr. trema "hole" + Gr. mese "middle" (fem.) + Gr. kleis "key, clavicle") (f) named for the foramen (opening) in the interclavicle [= Muraenosaurus]
Tricleidus Andrews 1909 "triple clavicle"
trie-KLIE-duhs (Gr. tri- "three" + Gr. kleid- (kleis) "key, clavicle" + -us) (m) named for the "peculiar clavicular arch," with "a large interclavicle and a pair of well developed elongated clavicles" on the front limb girdle. No complete skeleton is known. Tricleidus probably resembled Cryptoclidus, but as described by Brown (1981), its skull was shorter in the snout region and higher at the back where the parietal and squamosal bones meet. It also had fewer teeth, which differed from those of Cryptoclidus in having dense longitudinal ridges. Tricleidus was a relatively small trap-feeder that probably preyed on soft-bodied cephalopods and crustaceans. Brown (1981) originally classified the genus as an elasmosaurid, but later (Brown 1993) identified Tricleidus as a cryptoclidid.
Vertebrae: 26+ cervicals
Length: (estimated) 2.5-3 m. (8-10 ft.); skull: 22 cm. (8.7 in.))
Type Species: Tricleidus seeleyi [SEEL-ee-ie] Andrews 1909: "after the late Professor H.G. Seeley [1839-1909], who wrote a number of papers on these Oxford Clay Reptilia". (Holotype: BMNH R.3539) Plesiosauroidea Cryptoclididae Late Jurassic (Callovian) Eur.
Trinacromerum Cragin 1888 "three-tipped femur"
(Gr. trin- (from Gr. treis) "three" + Gr.
Vertebrae: 20 cervicals / 3 pectorals / 23 dorsals / 2-3 sacrals /
Length: 3 m. (10 ft.); skull: 54 cm. (21 in.); mandible: 56 cm. (22 in.))
Type Species: Trinacromerum bentonianum [ben-tohn-ee-AY-num]
Cragin, 1888 "from the Benton Formation (
Additional Species: Trinacromerum kirki [KUHR-kie] Russell
1935: for Prof. Stuart Raiburn Kirk, who collected and prepared the bones
shortly before his premature death; Loris Russell finished the preparation for
NOTE: "Trinacromerum bonneri"
Tuarangisaurus Wiffen & Moisley 1986 "ancient lizard"
too-ah-RUHNG-ee-SAWR-uhs (Maori tuarangi "ancient" + Gr. sauros "lizard") (m) named to indicate a large elasmosaur found in New Zealand (North Island, Manghouanga Stream), home of the Maori people; known from a skull (NZGS, CD425), part of the mandible and seven neck vertebrae belonging to an adult, as well as attributed postcranial remains of a number of juveniles.
Length: (estimated) 8-9(?) m. (26-30(?) ft.); skull (estimated): 37 cm. (14.7 in.))
Type Species: Tuarangisaurus keyesi [KEEZ-ie] for Ian W. Keyes,
a paleontologist "in recognition of his assistance and patient review of
papers over 15 years association, and for his contribution to New
Turneria Chatterjee & Small 1989 "for Turner"
(Turner + -ia) (f) named to honor Dr. Mort D. Turner "for his keen
interest in the
Uronautes Cope 1876 "tailed mariner"
yoor-o-NAW-teez (Gr. oura "tail" + Gr. nautes "mariner, sailor") (m) named to indicate a "short-necked genus" based on fragmentary "cervical, dorsal, and caudal vertebrae, with portions of the limb and rib bones." Welles (1952) described the material as "juvenile and indeterminate." Plesiosauria Late Cretaceous NA. [nomen dubium]
Woolungasaurus Persson 1960 "Woolunga lizard"
woo-LUHNG-guh-SAWR-uhs (Woolunga + Gr. sauros "lizard") (m) named for the Woolunga, a reptile-like beast in Australian aboriginal mythology; to indicate a large but somewhat primitive elasmosaurid plesiosaur found in Australia. Based on an incomplete fragmentary skeleton with neck vertebrae that were longer than high, indicating a fairly long neck (an advanced feature), but with coracoids that were not separated posteriorly to form a round or heartshaped opening, a feature found in all other known Cretaceous elasmosaurids. The adjoining coracoids resembled those of the earlier plesiosauroids instead--Persson (1960) viewed Woolungasaurus as an example of "mosaic evolution." A skull described in 1982 (Persson) is attributed to the genus; further study (Thulborn & Turner 1993) found evidence the skull had been bitten by a kronosaur, proving the smaller elasmosaur was prey to the giant pliosaur.
Length: (estimated) 7.5-9 m (25-30 ft.); skull: (estimated) 42 cm. (17 in.)
Type Species: Woolungasaurus glendowerensis [glen-dow-er-EN-sis]
Persson 1960: from Glendower station, Prairie, North Central Queensland,
Yuzhoupliosaurus Zhang 1985 "Yuzhou (
yoo-joh-PLIE-o-SAWR-uhs (Yuzhou + Pliosaurus (Gr. pleion "more" + Gr. sauros "lizard")) (m) named for Yuzhou, a former name for Chongqing [Chungking], a major city on the Chang Jiang [Yangzte] River in Sichuan Province, China, the region where the fossil was found. Known from a mandible, 18 vertebrae and fragments of the pectoral girdle (with a narrow scapula) and hindlimbs; a freshwater form.
Length: (estimated) 4 m. (13 ft.)
Type Species: Yuzhoupliosaurus chengjiangensis [chuhng-jyahng-EN-
sis] Zhang 1985: "from the Chang Jiang [Yangzte] River" (