Marine turtles from the Western Interior Sea
Copyright © 2004-2014 by
Last updated 03/02/2014
LEFT: A five-foot-long Hesperornis regalis swims over the top of a giant Protostega gigas turtle in the middle of the Western Interior Sea during the early Campanian. RIGHT: Brachauchenius takes a turtle out for lunch. Paintings copyright © 2005 by Dan Varner and may not be reproduced in any form without the express written permission of Dan Varner and Mike Everhart.
There were two major groups of marine turtles that lived in the Western Interior Sea during the Late Cretaceous; the Toxochelyids and the Protostegids. These turtles probably ate seaweed and jellyfish, or may have scavenged floating carcasses, much the same as modern turtles. Although their remains are found in the middle of the sea, the females must have periodically migrated hundreds of miles to the east or west to find sandy shorelines where they could lay their eggs above the high tide mark. Turtle bone found in the Smoky Hill Chalk is dense and very finely grained, and is readily differentiated from mosasaur or plesiosaur bone.
|Did mosasaurs eat turtles?
Well, according to most authors, including me, "Yes, they did." Do we have proof of that? Well, maybe.... In 1887, Louis Dollo, a respected Belgian naturalist published a paper in which he wrote (page 520), "Quoi qu'il en soit, le Hainosaure se nourrissait assurément de tortues marines, car nous en avons trouvé des restes dans sa carcasse."
Translated, he said, "However, Hainosaurus undoubtedly fed upon marine tortoises, because their remains have been found in its carcass."
Unfortunately he did not identify which specimens or where they were housed. Since Dollo's work is certainly well respected, most of us simply took his word for it. Recently I began asking questions about the whereabouts of the specimens that he was describing. While none have been located as of today (January, 2011), the search is on.
This crushing injury on a turtle shell fragment in the Teylers Museum in Haarlem, The Netherlands appears to indicate that it was bitten by something very large and powerful. It is likely that turtles in the Western Interior Sea were also eaten by the larger mosasaurs, initially by Tylosaurus and then by Mosasaurus and Prognathodon nearer the end of the Cretaceous.
REFERENCE: Dollo, L. 1887. Le hainosaure et les nouveaux vertébrés fossiles du Musée de Bruxelles. Revue des Questions Scienfiques XXI 504-539. (April 1887)
|In 2010, I became interested in finding the correct source of the family name
(Toxochelyidae) or this group of extinct marine turtles, which led me in circles for several hours
fruitless searching the Internet. There are many hits for “Baur 1895, emended by Zangerl (1953)” .... which goes exactly nowhere, since few papers I found actually
provide the full citation for Baur (1895).
However, my friend, the late Betsy Nicholls (1988) did cite “Baur, G. 1895. Ueber die Morphologie des Unterkiefers der Reptilien [On the morphology of the lower jaw of reptiles]. Anatomischer Anzeiger 11:410-415.” Unfortunately, that article by Baur turned out to be published in 1896, not 1895, and discusses the comparative anatomy of lower jaw of reptiles… and while Baur does illustrate a turtle dentary, he does not mention Toxochelyidae.
So far as I can determine, the family name Toxochelyidae was first used by Baur in another 1896 paper. The correct citation is:
Baur, G. 1896. Bemerkungen über die Phylogenie der Schildkröten
[Remarks on the phylogeny of turtles]. Anatomischer Anzeiger 12:561-570. The term “Toxochelyidae”
first occurs in print on page 564.
Hay, O.P. 1903. A revision of the species of the family of fossil turtles called Toxochelyidae, with descriptions of two new species of Toxochelys and a new species of Porthochelys. Bulletin of the American Museum of Natural History 21(10):177-185.
However, Hay(1908, p. 164) credits Baur as the source of the name, but again, provides no citation:
Hay, O. P. 1908. The fossil turtles of North America.
Carnegie Institution of Washington, Publication No. 75, 568 pp, 113 pl.
Zangerl, R. 1953. The vertebrate fauna of the Selma formation of Alabama, Part IV, The turtles of the family Toxochelyidae. Fieldiana, Geology Memoirs 3(4):
Baur (1896, p. 564) should be cited as the original source of the
family name Toxochelyidae.
Toxochelys latiremis Cope is the most common species of marine turtle found in the Smoky Hill Chalk in western Kansas.
|Toxochelyids - Toxochelys was a small to medium sized
turtle (up to 2 m (6 ft) in length) that is found throughout the chalk. This turtle was
similar in outward appearance to a modern leatherback turtle (i.e. the Green Turtle, Dermochelys coriacea) but is not closely related. Common fossils
include shell, limb and skull material. Several species have been described from the chalk
but T. latiremis is the most common.
LEFT: The type specimen (AMNH 2362) was described by Cope(1873) and figured in his 1875 Vertebrata (Plate VIII). It consists of a partial lower jaw (1 and 1a) and a coracoid bone (2), and was most likely collected from the Pierre Shale, and not the Smoky Hill Chalk as originally reported (See Nicholls, 1988).
|LEFT: The first complete skull of Toxochelys latiremis,
found by B. F. Mudge about 1876 (From Hay, 1908). It is interesting to note that skull and
limb material is found far more often than the carapace and plastron that covered the
turtle's body. Composed of thin bone under a leathery covering, it is likely that the
bodies of these turtles were quite edible to sharks, large fish, and mosasaurs.
RIGHT: Drawing of the skull of Toxochelys latiremis Cope - Dorsal view, from Williston, 1901). Click to enlarge. This figure is drawn from KUVP 1203 and KUVP 1212. KUVP 1203 is currently on exhibit (and difficult to photograph!)
|LEFT and RIGHT: Dorsal and ventral views of a small Toxochelys latiremis skull (VP -13449) that I collected in Gove County, Kansas in 1988. The skull was found lying upside down on top of the chalk, where it had recently eroded out, in one piece, and with the lower jaw still in place. Click here for a ventral view of the skull without the lower jaw; and here for a view of lower jaw. Parts of the anterior portion of the turtle's shell, neck vertebrae and front limbs were also found. It appeared that the skull, neck and front part of the shell had been severed by the bite of something fairly large... perhaps a Ginsu shark (Cretoxyrhina mantelli).|
|LEFT: Some of the limb bones of a medium sized Toxochelys
latiremis (FHSM VP-700) in the collection of the Sternberg Museum of Natural
History. The specimen was collected by M.C. Bonner in 1956 along Twin Butte Creek in
eastern Logan County. See Konuki 2008 for more information on this
RIGHT: The left humerus of FHSM VP-700 in dorsal and ventral views. (Adapted from Konuki 2008)
|LEFT: The left side of the pelvis and left rear limb
(minus foot) of FHSM VP-700. (Adapted from Konuki 2008)
RIGHT: The pectoral girdle and left front limb of FHSM VP-700. (Adapted from Konuki 2008)
|LEFT: The disarticulated shell and limb bones of a juvenile Toxochelys
latiremis (KUVP 1244) from the Smoky Hill Chalk.
RIGHT: A dorsal view of the skull of Toxochelys "brachyrhina" (KUVP 1215). This specimen was collected by E. P. West in Gove County sometime before 1898. See type specimen below.
|LEFT: Dorsal view of the type specimen of Toxochelys "brachyrhina"
Williston (KUVP 1212). Discovered in 1891 by S.W. Williston in the Smoky Hill Chalk
of Gove County, KS. Toxochelys "brachyrhina" is a junior synonym
of T. latiremis Cope.
RIGHT: Ventral view of the type specimen of Toxochelys "brachyrhina" Williston (KUVP 1212), including the lower jaw.
|LEFT: A well preserved skull of Toxochelys latiremis in dorsal
view... found as stomach contents of a shark (Squalicorax falcatus) in Logan
County, Kansas (see Druckenmiller, et al.,
1993) for more information. (University of Wisconsin-Madison, Museum of Geology)
RIGHT: Another view of the same specimen, showing other turtle bones and a fish vertebra (Ichthyodectes). The lower jaw had been separated from the skull and is shown here (upper right).
|Three views of a large toxochelyid skull (CMC VP-6947) from the Pierre Shale of Logan Co., KS. Donated by Pete Bussen to the Cincinnati Museum Center.|
|LEFT: Dorsal and ventral views of a smaller Toxochelyid skull (CMC VP-6948) from the Sharon Springs Member of the Pierre Shale of Logan Co., KS. Donated by Pete Bussen to the Cincinnati Museum Center. Note poor preservation due to the intrusion of calcite crystals into the bone. This a common problem in all vertebrate remains from the Pierre Shale in Kansas. It is of some interest to note that the type specimen of Toxochelys latiremis (AMNH 2362) was actually collected from the Pierre Shale by B. F. Mudge near McAllaster Butte in Logan County, and not in the Smoky Hill Chalk as is often assumed (see Cope 1875; Nicholls, 1988).|
|LEFT: PR 123 - Right and left humeri of Toxochelys latiremis
collected by George F. Sternberg from Logan County in the collection of the Field Museum,
RIGHT: PR 123 - Cervical vertebrae from the same specimen (Toxochelys latiremis).
|LEFT: A fragmentary specimen of Toxochelys latiremis (UNSM 50040) collected by George Sternberg in 1955 (GFS 103-55) from the Smoky Hill Chalk of Gove County, southeast of Oakley, Kansas, between Hackberry Creek and the Smoky Hill River. The specimen was purchased by the University of Nebraska State Museum.|
|LEFT: The lower jaw of a Toxochelys turtle
(FHSM VP-2006) collected by George Sternberg in 1949 from Gove County.
RIGHT: (FHSM VP-1344) The anterior portion of a lower jaw (right and left dentarys) of a large Toxochelys turtle collected from the upper Smoky Hill Chalk (MU 17) of Logan County.
|LEFT: Clockwise, dorso left-lateral view, ventral right-lateral
view and dorsal view of a slightly crushed cervical (?) vertebra from a Toxochelys
latiremis (FHSM VP-17432) specimen discovered in 2005.
RIGHT: We finally were able to recover the turtle remains in 2009 (The original site had been "lost" after a heavy rain in the summer of 2005)... Here are additional photos of the vertebrae from the neck, body and tail. (scale = cm)
|LEFT: The hyoplastron, hypoplastron and xiphiplastron of the FHSM
VP-17432, bones making up the left half of the turtle's lower shell (plastron). See
RIGHT: The broken right humerus of FHSM VP-17432. Based on a comparison with the humerus of FHSM VP-13449 (see skull above), these two specimens would have been about the same size.
|LEFT: Field shot of the hyoplastron of FHSM VP-17432.
RIGHT: The dig site where FHSM VP-17432 was discovered. Hattin's marker unit 7 was about 5 cm below the turtle bones...
LEFT: The fragmentary remains of a small toxochelyid (?) turtle (FHSM VP-17464) that I collected in 1991 from southeastern Gove County. Pieces of the carapace / plastron had eroded out earlier and were scattered over a wide area.
RIGHT: (FHSM VP-17018) A fragment (peripheral or marginal bone) from the carapace of a large turtle, probably Toxochelys, found in Gove County (Late Coniacian). Note the bite marks from a large shark (Cretoxyrhina) on the right side of the fragment in the lower frame. This piece was the only part found of the turtle. The thin shells of even the largest turtles were no match for the strong jaws and sharp teeth of predators. Go here for a photo of a modern Loggerhead turtle bitten by a large shark, most likely a Great White. (Photo by Adam McKinnon, used with permission).
|LEFT: Keith Ewell and I collected fragments of an even smaller
individual (FHSM VP-17572) in July, 2009....Probably newly hatched, this little one didn't live very
long. Shell was less than 4 inches long.
RIGHT: The remains of a very small (hatchling) turtle (FHSM VP-17466) discovered by Keith Ewell in the lower chalk of western Trego County in July, 2009. Although the remains are too fragmentary for a positive identification, they are most likely from a baby Toxochelys latiremis.
|LEFT: A cast of a small but complete specimen of Toxochelys
latiremis in dorsal view. Another view is HERE.
The upper shell is called the carapace.
RIGHT: The same cast of a small but complete specimen of Toxochelys latiremis in ventral view. The lower shell is called the plastron. Cast by Triebold Paleontology, Inc.
Note that Gudger (1949) reported the remains of marine turtles in the stomachs of 5 out of 5 Tiger sharks (Galeocerdo tigrinus) that were caught near Key West, Florida. It appears that things haven't improved much for turtles in 85 million years.
|The type specimen of Toxochelys bauri (YPM 1786)
was collected by Charles H. Sternberg about 1904 from the Smoky Hill Chalk
in western Gove County, Kansas. It was subsequently described by Wieland
in 1905, who published these figures and
a photograph of the reconstructed carapace. The actual
bones present are shown here. The carapace is a 39 cm (15 in) by 23 cm
(14 in). It was named in honor of Georg Baur (1859-1898).
FAR LEFT: Reconstructed dorsal view of the carapace of Toxochelys bauri (neurals, ribs and marginals / peripherals).
LEFT: Left lateral view of same specimen.
RIGHT: Ventral view of same specimen, showing the components of the plastron. (Abbreviations: en - entoplastron; h - hyoplastron; hp - hypoplastron; x - xiphiplastron.
Chelospargis advena - The type specimen of Protostega advena (KUVP 1219) was described by Hay (1908). It was collected by S.W. Williston in 1891, probably from Gove County. While showing some protostegid characters, it is a relatively small individual with only a little cranial or limb material present in the specimen. The genus name was changed to Chelosphargis by Zangerl in 1953.
|LEFT: The type specimen of Chelospargis advena
in the collection at the University of Kansas.
RIGHT: Figures 256-259 from Hay (1908) of the type specimen. Zangerl (1953, fig. 21) figured the skull, mandible and hyoid.
|LEFT: The peripherals (marginals) of a partial carapace of a
very small Chelospargis advena turtle that
I discovered in 1996 in Gove County, between MU 6 and MU7. The shell would have been about 3 inches wide and less than 6 inches
long. The Western Interior Sea would not have been a good place to be for a turtle this
size! The remains indicate that it was probably bitten in two by a larger predator,
probably a shark.
RIGHT: A similar sized specimen of Chelospargis advena (KUVP 1258) showing the distinctive shape of the peripheral bones that make up the rim of the carapace. Another specimen in the Yale Peabody collection (YPM 3601) is shown here.
|LEFT: The remains of another small Chelospargis turtle (FHSM
VP-17463) collected in 1989 (EPC 1989-31) from the Smoky Hill Chalk in southern Gove
County. The remains show evidence of scavenging (serrated bite marks) by Squalicorax
and it appears that both front paddles had been bitten off.
RIGHT: The severed humeri of FHSM VP-17463, possibly evidence of predation / scavenging by a larger shark like Cretoxyrhina.
|LEFT: The type specimen of Prionochelys galeotergum
(CMNH PR125) from the Smoky Hill Chalk of Gove County, Kansas, collected
by G.F. Sternberg in 1931 and sold to the Chicago Museum of Natural
History (Specimen is now in the Field Museum). The genus and species were
described by Zangerl (1953).
RIGHT: Figure 114 from Zangerl (1953) showing a comparison of the "saw-back" dorsal keel of Prionochelys in lateral view among the three known species. Prionochelys nauta and P. matulino are found in Late Cretaceous Gulf Coast deposits.
HERE is a model of Prionochelys nauta reconstructed by the Rocky Mountain Dinosaur Resource Center (Triebold Paleontology, Inc.)
|BELOW: Note that, contrary to some
Internet web pages that credit the name to Sternberg (1904), this species
was actually named by two other authors in 1905. Charles Sternberg never
named a species of anything that he collected and in
1907 credits Wieland with the name.
Ctenochelys stenopora (Yale Peabody Museum collection; YPM-1786) was collected by C. H. Sternberg on December 14, 1904, near Monument Rocks in western Gove County, Kansas. It was originally named Toxochelys bauri Wieland (1905), AND Toxochelys stenoporus by Hay (1905). Apparently Hay's name had precedence and Hay (1908) changed the species name to stenopora. Zangerl (1953, p. 227) assigned the species to a new genus (Ctenochelys) and used Hays 1908 revision of the species name. Matzke (2007) referred back to Hay's original species name.
LEFT: A nearly complete carapace and plastron of Ctenochelys stenopora in the University of Wisconsin-Madison collection.
|LEFT: The skull of Ctenochelys stenoporus in
dorsal and ventral views as figured originally by Case (1898).
RIGHT: A partial carapace of the type specimen of Ctenochelys stenoporus as figured by Case (1898).
|Originally described as Toxochelys stenoporus by
E.C. Case in 1898, it was recognized as a new genus by Hay (1905)
LEFT: Skull of the type specimen at the University of Kansas Museum of Natural History as figured by Hay (1905).
RIGHT: Lower jaw of the type specimen at the University of Kansas Museum of Natural History as figured by Hay (1905).
LEFT: The carapace and lower jaw of a small Ctenochelys stenopora turtle in the collection of the Keystone Gallery. The carapace is about 8 inches long. See Sternberg (1907) for a brief description of this turtle. See Matzke 2007 for comments on nearly complete specimen (USNM 357166).
RIGHT: A detail from a mural painted by Charles Bonner (Keystone Gallery) showing what these small turtles might have looked like when they were living in the Western Interior Sea.
Cynocercus incisus - The second turtle to be described from the Smoky Hill Chalk.
|While Cope was collecting fossils in western Kansas in 1871, one of the
Army personnel (Sgt. William Gardner) assigned to escort him found two
caudal vertebrae of a
small turtle "two or three hundred yards" from the type locality of Protostega
gigas, southeast of Fort Wallace. Although the remains were very
limited, Cope (1872)
described and named the species Cynocercus incisus in an article read before the
American Philosophical Society on January 19, 1872. Lane (1946) considered them to be very
similar to Toxochelys, and if so, the name would have precedence by date.
LEFT: Two caudal vertebrae of Cynocercus incisus (AMNH FR1583), in left lateral, ventral, anterior and posterior views; republished by Williston (1898) from Cope (1875, Plate VIII). A metapodial (3.4 cm in length) is also included with the specimen.
Porthochelys laticeps Williston 1901 - Holotype
|Porthochelys laticeps (KUVP 1204) is a one-of-a-kind specimen...
the only one collected so far.
LEFT: The reconstructed carapace, skull and right humerus of the holotype specimen of Porthochelys laticeps (KUVP 1204). The specimen was collected by E. H. Sellards and J. T. Shearer from the Smoky Hill Chalk near the Saline River in Trego County, KS. The shell is about 60% complete and is 30 in. long by 29 in wide. It is unusual for a Late Cretaceous marine turtle because of its solid construction (most modern marine turtles, however, have solid shells). The specimen was described and named by Williston in 1900 and is on exhibit at the University of Kansas Museum of Natural History.
RIGHT: A left oblique view of Porthochelys laticeps (KUVP 1204). Small bone at lower right is the right humerus, in ventral view.
|LEFT: The skull of KUVP 1204 measures 4.5 in (11 cm ) long by 4.5 in
(11cm) wide across the quadrates.
RIGHT: Drawings of the distinctive skull and lower jaw of Porthochelys laticeps as published in Williston, 1901. More of Williston's original illustrations are here: Plate XIX, Figure 1 (Lower jaw, dorsal view); Plate XIX, Figure 2 (Skull, dorsal view) Williston provided figure showing the skull of Toxochelys latiremis for comparison.; Plate XX (Skull, ventral view); Plate XXI (Carapace, dorsal view); Plate XXII (Humerus and plastron, dorsal view).
Based on the rareness of Porthochelys remains in the Western Interior Sea, it seems likely that this species lived somewhere else (possibly near shore / fresh water).
Desmatochelys lowi Williston 1894
Desmatochelys lowi Williston 1894 (KUVP 1200) is probably the oldest marine turtle yet described from the Midwest. Fragmentary turtle remains have been reported by Beamon, 1999, from the Kiowa Shale (Early Cretaceous, Albian) of McPherson County, KS, but they are otherwise unidentifiable. The fairly complete specimen of Desmatochelys lowi was collected from the "Benton Cretaceous" near the town of Fairbury in Jefferson County, Nebraska in 1893. This locality is just north of the Kansas-Nebraska state line and other remains (KUVP 32401 and 32405) of this species have been found in Kansas. From the excellent, 3-dimensional preservation of the skull (below), it is likely the remains came from the Fairport Chalk Member of the Carlile Shale and are Middle Turonian in age. Right lateral, dorsal and ventral views of the skull of the type specimen (KUVP 1200) are shown below. A photograph of the lower jaw is HERE. The photographs were taken in January, 2004.
NEW - See the dig of the first Desmatochelys skull found in Kansas.... September, 2008
|LEFT: A right lateral view of the skull of Desmatochelys
RIGHT: A dorsal view of the skull of Desmatochelys lowii
|LEFT: A ventral view of the skull of Desmatochelys lowii. Note
that the round hole visible at the back of the palate was drilled there for mounting
purposes when it was originally on exhibit.
RIGHT: Drawings of the skull of Desmatochelys lowii adapted from Hay, 1908.
|LEFT: A new specimen of Desmatochelys lowii
(FHSM VP-17470) from the
Smoky Hill Chalk of Mitchell County, KS. The specimen was
discovered in 2008 by Gail Pearson.
RIGHT: The left front paddle of the new turtle specimen.
|LEFT: (May, 2010) - Here is the ventral side of the
skull and lower jaws after additional preparation and cleaning by Dennis
Roth at the Sternberg Museum of Natural History. (Photo by Dennis
Roth) The specimen was
discovered in 2008 by Gail Pearson.
RIGHT: (May, 2010) - This is the first view of the dorsal side of the skull (FHSM VP-17470) since we put the plaster and burlap jacket on it in September, 2008 (Additional preparation and photograph by Dennis Roth, Sternberg Museum of Natural History, Hays, Kansas). Note that while this skull is badly crushed and not as photogenic as KUVP 1200, it is more complete, and is certainly the best (and only) skull of Desmatochelys lowii ever collected in Kansas.
The only turtle remains known from the Greenhorn Limestone in Kansas
|Turtle remains are very rare in the Greenhorn Formation.
LEFT: A single turtle caudal vertebra (FHSM VP-17571) from the basal Lincoln Limestone Member of the Greenhorn Formation in Russell County, Kansas.
RIGHT: The edge of the plastron (marginal or peripheral), the proximal end of a rib and a part of the skull of a toxochelyid turtle from the basal Greenhorn of Lincoln County, KS. Collected by Keith Ewell in June, 2005.
The endocast of a possible marine turtle from the Dakota Sandstone of Republic County, Kansas
|LEFT: Dorsal view of the endocast (from the inside the shell) of a
possible marine turtle from the Middle Cenomanian Dakota Sandstone of Republic County,
Kansas. The specimen is housed in the Republic County Historical Society Museum,
RIGHT: Ventral view of the endocast (from the inside the shell) of a possible marine turtle from the Middle Cenomanian Dakota Sandstone of Republic County, Kansas. A side view is HERE.
A marine (?) turtle from the Kiowa Shale (Albian, Early Cretaceous)
|LEFT: The carapace (upper shell) of a medium sized turtle (KUVP 16370)
found in the Kiowa Shale of Kiowa County, Kansas. The specimen was discovered by
Orville Bonner in June, 1969 and was tentatively identified as Glyptops sp.
It is possible that Glyptops was not a fully marine species. However, the specimen
was found in off-shore marine sediments. Anterior is to the left.
RIGHT: The plastron (lower shell) of the same specimen. This is probably one of the oldest turtle specimens known from Kansas, but it is as yet unreported. Anterior is to the left in both photos.
|LEFT: Dorsal and ventral views of a large turtle shell fragment
(FHSM VP-13551) from the Kiowa Shale (Albian, Early Cretaceous) of
McPherson County, KS. The same deposit also includes crocodile remains and it is possible
that these crocodiles fed upon the turtles, and/or that their shells were simply battered
apart by waves in the high-energy, near shore environment.
RIGHT: A collection of turtle shell fragments from large, early Cretaceous turtles in the Kiowa Shale of McPherson County, KS.
Protostega gigas and Archelon ischyros were giant (Volkswagen-sized!) sea turtles that are found in Cretaceous deposits.
Note that the first known Protostega specimen (YPM 1408) was collected on July 4 by the 1871 Yale College Scientific Expedition, eight miles east of Fort Wallace, almost 5 months before Cope arrived in Kansas. However, it has never been described.
|E. D. Cope found and collected the type specimen of Protostega
gigas during his only trip to the Kansas chalk in 1871. He wrote about his
experiences, including the discovery of Protostega, in a
letter dated October 9, 1871 to Professor Lesley of the American Philosophical
"On another occasion, we detected unusually attenuated bones projecting from the side of a low bluff of yellow chalk, and some pains were taken to uncover them. They were found to belong to a singular reptile, of affinities probably to the Testudinata, this point remaining uncertain. Instead of being expanded into a carapace, the ribs are slender and flat. The tubercular portion is expanded into a transverse shield to beyond the capitular articulation, which thus projects as it were in the midst of a flat plate. These plates have radiating lines of growth to the circumference, which is dentate. Above each rib was a large flat ossification of much tenuity, and digitate on the margins, which appears to represent the dermo-ossification of the Tortoises. Two of these bones were recovered, each two feet across. The femur resembles in some measure that ascribed by Leidy to Platecarpus tympaniticus, while the phalanges are of great size. Those of one series measured eight inches and a half in length, and are very stout, indicating a length of limb of seven feet at least. The whole expanse would thus be twenty feet if estimated on a Chelonian basis. The proper reference of this species cannot now be made, but both it and the genus are clearly new to science, and its affinities not very near to those known. Not the least of its peculiarities is the great tenuity of all the bones. It may be called Protostega gigas." E. D. Cope, 1871
LEFT: A reconstruction of the skeleton of Protostega gigas (USNM 11651) in the exhibit at the Smithsonian Institution, Washington, D.C. This reconstruction is based on a specimen purchased from G.F. Sternberg.
(1872, p. 433) described the discovery and recovery of the type specimen:
LEFT: Cope (1875, Plate
XIII) – “Two dermal bones of Protostega
gigas” - Portions of the plastron of the type specimen of Protostega
gigas (AMNH FR 1503) mis-identified by Cope as part of the carapace.
They were later correctly identified by Baur (1886) and Hay (1895).
RIGHT: The left humerus of the type specimen of Protostega gigas (Cope, 1875, Plate XII). Cope (1872) noted that it was one foot (0.3 m) in length.
Cope (1872) estimated the head to tail length of the animal at 12.8 feet; Hay (1895) disagreed with Cope's assumptions, but arrived at the same overall length:-3.9 m
Hay (1908, p. 191) wrote: "The specimen of this species which
Cope originally described was found by him in 1871, in Niobrara deposits,
near Butte Creek, south of
As stated by Cope, the remains preserved include many parts of the skull; 5 vertebræ,
From his study of his materials Cope arrived at the conclusion that Protostega was a
|LEFT: The left plastron from the type specimen of Protostega
gigas Cope 1872 as published on Plate IV by Hay, 1895. It measures 1.2 m (almost 4 ft)
from left to right and came from a turtle that measured about 3.0 m (10 ft) long (from
nose the end of the tail). The specimen is curated in the American Museum of Natural History as
FR 1503. (Anterior to the left). "This plate represents the hyoplastron
and hypoplastron of the left side of Protostega gigas seen from below. A view is
also given of the nuchal bone." (Hay, 1895). Hay stated that the
combined length of the hyoplastron and hypoplastron (at left) was 1.2 m (4
RIGHT: Plate V from Hay 1895: “A
partial restoration of the plastron of Protostega,
to show the relative positions of the bones and the size of the fontanelle.
Only the bases of the epiplastra and of the xiphiplastra are shown.”
|LEFT: The skull of the type specimen of Protostega
gigas (AMNH 1503) in left lateral view from Hay, 1908, fig. 247. Hay
(1908) noted that : "Cope
had considerable portions of the skull and most of these he figured. The
writer has studied these bones and has found that in most cases Cope's
determinations were incorrect. Baur had also examined these cranial bones
and accepted Cope's determinations (American Naturalist, xxiv, 1890, p.
247 represents these bones, each having its name indicated. Cope's
determinations are indicated in parentheses."
RIGHT: The carapace of CMNH 1421 in ventral view from Wieland (1906, fig. 2), showing the dorsal vertebrae and the very limited extent of the costal plates (less than 1/3 the length of the ribs).
|LEFT: Protostega gigas - a detail from a mural
painted by Charles Bonner in the Keystone Gallery (© Charles Bonner, Keystone
RIGHT: Archelon ischyros (adapted from Berry, 1929). Of the two, only Protostega is found in the chalk and generally only in the upper chalk. Somewhat like modern leather back sea turtles in overall appearance, they still retain a portion of their original bony shell. The Protostegids may have migrated in and out of the Western Interior Sea. Fossilized remains are relatively rare, but nearly complete skeletons from the Kansas chalk are found in many museums.
|LEFT: Four views of the upper (proximal) end of a small
protostegid humerus, probably severed and partially digested by a large shark, found in
the Late Coniacian chalk of Gove County by Pam Everhart in 1990. This may be an unusually
early occurrence of this genus. (FHSM VP-17557)
RIGHT: Figure 3 from Wieland (1906) showing the right humerus of Protostega gigas (CMNH 1421) in dorsal view. The bone is 34 cm (13.4 in) long.
|BELOW: Left: Pam Everhart works on the partial remains of a Protostega gigas that she discovered in July, 1994 in Logan County, Kansas. Center - Most of the left half of the turtle's plastron (lower shell) is exposed here in dorsal view. Right: Removed from the chalk, the 'spiky' look of the plastron (ventral view) is very apparent. We donated this specimen to the Sternberg Museum in 1997 where it is curated as FHSM VP-13448 (Our EPC 1994-42). About 30 inches in maximum length, anterior to the left. See a photo of a composite Protostega plastron here.|
|LEFT and RIGHT: Close up views of damaged areas that are visible on the anterior and posterior lobes of this plastron (More recent photo here) in ventral view. These appear to abrasions that might have resulted as a large, heavy female turtle dragged herself across a sand beach to lay her eggs. (added October 28, 2006)|
|LEFT: The partial carapace and plastron on a large Protostega
gigas collected and prepared by George F. Sternberg (4886-A) and later acquired by
the United States National Museum (Smithsonian). Sternberg noted that the specimen
was found without limbs or skull. It is likely that this specimen served as the basis for
the reconstruction above.
RIGHT: The skull, lower jaw and other fragments from another Protostega specimen that was collected by George Sternberg in the 1920s and sent to the University of Nebraska State Museum. It is probably the same specimen as shown below. Both photos from Sternberg archives, Forsyth Library, Fort Hays State University.
|LEFT: A wall-mounted reconstruction of the partial remains of a
Protostega gigas turtle in ventral view at the University of Nebraska State Museum.
Collected by George F. Sternberg (GFS 103-31)
RIGHT: The skull of the turtle shown at left in right lateral view. Note that Protostega lacks the large bony extension of the beak (premaxilla) found in Archelon.
|LEFT: The exhibit specimen of Protostega gigas in the
Denver Museum of Nature and Science. This specimen was collected by George F. Sternberg in
late 1945 (GFS 10145) from Logan County.
RIGHT: Left lateral view of the skull of the exhibit specimen in the Denver Museum of Science and Nature. Click here for an original photo of the skull.
|LEFT: Photograph (circa 1945) by George F. Sternberg of the above
Denver Museum Protostega gigas in dorsal view. As described by Sternberg, this
was probably a juvenile turtle with a shell that is about 3'8" wide... and a length
of about 5 feet from tip of beak to the back edge of the carapace
RIGHT: Right lateral view of the same specimen as prepared and photographed by G.F. Sternberg about 1945. Sternberg's field number on this specimen was 10145 (the 101st specimen he collected in 1945). The specimen is about 5 feet in length, with a maximum shell width of 44 inches. Sternberg also noted that the skull was 16 inches long.
|LEFT: An early photo by C.H. Sternberg of Protostega gigas
from the chalk of western Kansas. The specimen is actually a composite of two
specimens (CMNH #1420 and #1421), both discovered by Sternberg about "three miles
northwest of Monument Rock" in western Gove County in 1903 and acquired by the Carnegie Museum of Natural
History in Pittsburgh, PA in 1904. Sternberg (1906) noted that this specimen
measured 10 feet (3 m) across the front paddles. A more recent picture is HERE.
RIGHT: A dorsal view of a Protostega gigas (FHSM VP-79) carapace and plastron on exhibit at the Sternberg Museum of Natural History. This specimen was collected by George Sternberg. (about 4 ft x 4 ft). Side view
| In 1897, E.C. Case described two Protostega
specimens in an article in the Journal of Morphology. Although Case does
not identify the specimens by number, it is likely they were in the
collection of the Field Museum in Chicago, IL.
LEFT: A medial view of the mandible of Protostega gigas.
RIGHT: Plate V from Case, 1897: Fig. 1. Supraoccipital. The badly crushed petrosal and paroccipital are not shown; Fig. 2. Exoccipital. Right side; Fig. 3. Basioccipital. a, from above; b, from below; Fig. 4. Petrosal. a, from within; b, from without; Fig. 5. Paroccipital. Right side; Fig. 6. Quadrate, pterygoid, and palatine. Right side; Fig. 7. Quadrate-jugal. Right side; Fig. 8. Lower jaw. [Dorsal view]; Fig. 9. Xiphiplastron. Left side, showing attachment with hypoplastron and xiphiplastron of right side; Fig. 10. Nuchal plate; Fig. 11. Fifth and sixth peripherals. Left side.
|LEFT: Plate IV from Case, 1897. Photograph
of plastron with nuchal plate and peripherals. (Dorsal view)
RIGHT: Plate VI from Case 181917. Fig. 12. Humerus. Right side; Fig. 13. Scapula. (See PR127); Right side; Fig. 14. Coracoid. Right side. Fig. 15. Pubis. Right side; Fig. 16. Ischium. Right side; Fig. 17. Ilium. Right side (taken from smaller specimen); Fig. 18. Femur. Left side; Fig. 19. Rib head. (Taken from smaller specimen).
|LEFT: UR 79 - A nearly complete left half of the plastron of a
large Protostega gigas in the collection of the Field Museum, Chicago, IL. This
specimen was described and figured by O.P. Hay (1895).
RIGHT: UR 90 - The anterior portion of the left plastron of a large Protostega gigas in the collection of the Field Museum, Chicago, IL. Note the bite marks at the upper right. These were probably the result of scavenging by a large shark (Cretoxyrhina mantelli). Click HERE for a closer view.
|LEFT: A fragment of a Protostega plastron collected from
Graham County that preserves large and deep bite marks, probably from a Ginsu shark (Cretoxyrhina
RIGHT: The proximal end of a large Protostega gigas humerus (UW-M VP1503-57) from the upper chalk of western Logan County with deep gouges from the teeth of a large shark.
|LEFT: The right front limb and shoulder of Protostega gigas,
adapted from Hay (1908).
RIGHT: The right half of the pelvis and right hind limb of Protostega gigas, adapted from Hay (1908).
| LEFT: The skull and right front limb of the
Carnegie Museum No. 1421 Protostega gigas, collected by Charles H.
Sternberg from the Smoky Hill Chalk along Hackberry Creek in Gove County,
Kansas (Adapted from Wieland 1906, Figure 1).
RIGHT: The right front limb of No. 1421 reconstructed by Wieland (1906, fig. 4)
|LEFT: The right hind limb of a large Protostega gigas turtle
(KUVP 1201) in the University of Kansas Museum of Natural History. It was collected by
Charles Sternberg in 1900 somewhere west of Russell Springs in Logan County. This specimen
was one of the first examples of the rear limb of this giant turtle ever found, and was
the subject of a paper by S. W. Williston in 1902. See a
colorized version of his Text-Figure 1 here. The femur (upper leg bone) is
cm (14 in) long. The entire limb would have been about 4 feet long.
RIGHT: The right hind limb of Protostega gigas as reconstructed by Wieland (1906, fig.5).
|In the summer of 1903, Charles Sternberg collected a
fairly complete specimen of a turtle that he identified as Protostega
gigas. Later that year he noted that it would take another year to
finish the preparation of this remains. His oral report at the annual
meeting of the Kansas Academy of Science wasn't published until 1905. The
paper included two photographs of the specimen during preparation. The
specimen was sold to the Carnegie Museum of Natural History and is
designated as #1420.
Sternberg, C. H. 1905. Protostega gigas and other Cretaceous reptiles and fishes from the Kansas chalk. Kansas Academy Science, Transactions 19:123-128.
LEFT: Plate XVIII shows the vertebral column from neck to tail, including the ribs.
RIGHT: Plate XIX shows the pelvis and hind limb, part of the shoulder and one front limb.
|As described by H.F. Osborn (1904) in Science:
skeleton lay on its dorsal surface with the fore limbs stretched out at
right angles to the median line of the carapace, measuring six feet
between the ungual phalanges; the hind limbs were parallel with the neural
arch, and stretched out behind.
LEFT: Plate 31 from Wieland (1906): a)
Right and left shoulder girdles, with right front flipper and the proximal
half of the left humerus; b) Pelvic girdle with both hind flippers; c) The
RIGHT: Plate 32 from Wieland (1906): Enlarged views of the
forearm and hand (right photograph) and the foot (left photograph).
| Click here for the dig
of the newest (2011) Protostega gigas specimen from the Smoky Hill
LEFT: The cast of FHSM VP-17979, courtesy of Anthony Maltese, Triebold Paleontology, Inc.
Microstega (Protostega) Copei - The type specimen of Protostega copei (YPM VP 1787) was collected by Charles Sternberg from along Hackberry Creek in Gove County, Kansas. It was named and first described by Wieland in 1909. Later, Zangerl (1953) changed the genus name to Archelon, and Hooks (1998) redescribed it again as Microstega.
|LEFT: The reconstructed skull of Protostega copei (YPM
VP 1787) in right lateral view as figured by Wieland in 1909. The
specimen was collected in the summer of 1905 by Charles H. Sternberg from
the Smoky Hill Chalk along Hackberry Creek in southern Gove County, KS.
The specimen was subsequently referred to the genus Archelon by
Zangerl (1953) and later described as a new genus (Microstega) by
RIGHT: The pectoral and pelvic girdles of Protostega copei in dorsal view as figured by Wieland in 1909.
|LEFT: The carapace of Protostega copei (YPM
VP 1787) in dorsal
view as figured by Wieland in 1909. Wieland reported that the carapace was
on exhibit in the Yale Peabody Museum in 1909, but I did not see it in
RIGHT: The plastron of Protostega copei in dorsal view as figured by Wieland in 1909.
The following information was provided by Dr. Kraig Derstler of the University of New Orleans. Kraig is one of the few people currently studying protostegid turtles.
"Very little is written about Protostegids, other than the descriptive stuff by Wieland and his colleagues in the 1890's and earliest 1900's. Protostega is a huge-headed sea turtle. The species are pretty poorly defined at present. Specimens come from the Niobrara of Kansas, the Pierre of Kansas, Colorado, Wyoming, and South Dakota, the Mooreville, Demopolis, and Eutaw formations of Alabama and Mississippi, and the Campanian - Santonian marls of Texas. Possible scraps also come from other Santonian-lowermost Maastrichtian deposits around the world. Other Protostegids (Calcarichelys, Chelosphargis, and a couple of unnamed things) range from the Albian through the latest Maastrichtian worldwide.Archelon ischyros has a normal-sized skull, proportionally much smaller than Protostega. However, it has that distinctive hooked snout. It is so far confirmed only from the upper half Pierre in South Dakota. (Reports from Colorado and elsewhere are pretty unbelievable.)
I've never seen any Niobrara Protostega material from an animal that was more than about 2-2.5 m long. Niobrara giants may have existed, but I haven't seen any evidence. And, I've never seen any signs of Archelon in the Niobrara. However, there are lots of small to medium-size Chelosphargis specimens and possibly some pieces of the "thorny Protostegid" Calcarichelys". ( Dr. Kraig Derstler )
Concerning size, the largest Protostega is a 3.4 m beast in the Dallas Museum of Natural History. I was consultant for this exhibit and I'm pretty confident of the identification as well as the size. The Yale Archelon is 3.0-3.1 m, but another I've studied is 4.6 m long! It is virtually perfect and articulated. As a result, the size and the identification are both solid.
RIGHT: The right front limb of a Protostega gigas turtle discovered in the Cretaceous of Greene County, Alabama in 1933 (from Renger 1935). The humerus is 42 cm long and came from an animal with a shell length of 150 cm (5 ft). Renger estimated that the animal when alive would have weighed 2.5 to 3 tons.
Archelon ischyros (Go here for another website about Archelon)
|Williston made an interesting comment regarding the stratigraphic occurrence of various Late Cretaceous genera that is worth repeating here. He (1902, p. 270) noted that the characters separating Archelon Wieland from Protostega Cope, while not very important, would seem sufficient. Nevertheless, one can derive little justification from the different geological horizons in which the forms are found. The relations between the Niobrara and Fort Pierre vertebrates are for the most part very close. I have recognized in both horizons Tylosaurus, Platecarpus and Mosasaurus (Clidastes), as well as Pteranodon and Hesperornis, all very typical of the Niobrara deposits, and the existence of Claosaurus [Marshs dinosaur discovery in Kansas] has been recently affirmed in the Fort Pierre. On lithological grounds, there is nothing separating the two groups of deposits and I protest against the names Colorado and Montana, as perpetuating a wrong impression. On paleontological and lithological grounds, there would be much better reasons for uniting the Niobrara with the Fort Pierre than with the Fort Benton.|
LEFT: Two views of "Archelon ischyros, a gigantic sea-turtle from the Upper Cretaceous of South Dakota" by S. W. Williston, 1914 (Fig. 126).
|LEFT: A right lateral view of the skull of Archelon ischyros,
adapted from Hay (1908) from the original in Wieland (1900). Note the distinctive hooked
premaxilla which was covered with a horny beak in life, similar to what is seen in modern
RIGHT: The cast of a very large Archelon ischyros skull from South Dakota (Vienna specimen- below). Scale is 10 cm (about 4 inches). A dorsal view of the skull is HERE
|LEFT: A cast of the "Vienna Archelon" recently on display at the Sternberg Museum of Natural History, Hays, KS. The original specimen was found in 1976 in the upper Pierre Shale of South Dakota and is on exhibit in the National Natural History Museum in Vienna, Austria. It measures about 15 feet from the tip of the beak to the tip of the tail... and about 16.5 feet across the outstretched front paddles. More information HERE.|
LEFT (Dorsal) AND RIGHT (Ventral): Old pictures of the type specimen of the protostegid Archelon ischyros (YPM-3000) in the Yale Peabody Museum. It was collected from the upper Pierre Formation of South Dakota in 1895 by Dr. G. R. Wieland, and described by him in 1896. While very similar to Protostega, it is much larger and lived several million years after the Smoky Hill Chalk species. (Click on LEFT photo to enlarge) .... A larger view is HERE
|LEFT and RIGHT: Large photos of the type specimen of Archelon
ischyros published Wieland in 1909. I hadn't seen these photos
before... not sure if they have ever been reproduced or not.
|BELOW, left to right -- Drawings from Wieland (1909) of the same skeleton of Archelon: 1) From above; 2) From below without plastron; and, 3) From below, with plastron. Note the missing right rear limb. Wieland (1909) explained that the right tibia and fibula had been "cleanly severed" at sometime before the turtle died. The right femur is intact.|
|Archelon ischyros, adapted from Wieland, 1909. (CLICK TO
FAR LEFT: Dorsal view
LEFT: Ventral view
RIGHT: Ventral view, plastron removed.
|LEFT: The carapace and ribs of Archelon ischyros (adapted
from Wieland, 1896)
RIGHT: The plastron (lower shell) of Archelon ischyros (adapted from Hay (1908), originally from Wieland (1898)). Note that Wieland was unsure that Archelon was a separate genus in the Protostegidae, and briefly renamed his A. ischyros as Protostega ischyra in order to include it within that genus. The revision was brief and was not accepted. (head is to the top)
LARGE MARINE TURTLES FROM EUROPE - THE NETHERLANDS (Maastrichtian Age)
|LEFT: The very well preserved skull of Allopleuron hoffmanni,
associated with a large part of the skeleton in exhibits of the Maastricht Museum of
Natural History, Maastricht, The Netherlands.
RIGHT: The crushed skull of Allopleuron hoffmanni in the exhibits of the Teylers Museum, Haarlem, The Netherlands.
|LEFT: A fragment of turtle bone showing bite marks in the exhibits
of the Teylers Museum, Haarlem, The Netherlands.
RIGHT: A fragment of a turtle carapace showing the results of a crushing bite by a large mosasaur, probably Prognathodon, in the exhibits of the Teylers Museum, Haarlem, The Netherlands.
LARGE MARINE TURTLE FROM MOROCCO (Upper Campanian - Maastrichtian AGE)
|LEFT: A large marine turtle from the phosphates of Morocco
RIGHT: A dorsal view of the shell of a large marine turtle from the phosphates of Morocco.
|This Oceans of Kansas Paleontology web page has been selected as a resource by the Encyclopedia Britannica (October 2006). Click here to search for more information on prehistoric and modern marine turtles:|
Agassiz, L. 1849. [Remarks on crocodiles of the Green sand of New Jersey and on Atlantochelys]. Proceedings of the Academy of Natural Sciences of Philadelphia. 4:169.
Baird, D. 1978. Pneumatoarthrus Cope, 1870, not a dinosaur but a sea-turtle. Proceedings of the Academy of Natural Sciences of Philadelphia 129(4):71-81.
Baird, D. 1984. Evidence of giant protostegid sea-turtles in the Cretaceous of New Jersey. The Mosasaur 2:135-140.
Baur, G. 1886. Osteologische Notizen uber Reptilien.
Zoologischer Anzeiger 9:685-690, 733-743.
Dermochelys Biologisches Zentralblatt, 9:
Baur, G. 1896. Ueber die Morphologie des Unterkiefers der
Reptilien. Anatomischer Anzeiger 11:410-415.
G. 1896. Bemerkungen über die Phylogenie der Schildkröten. Anatomischer
Beamon, J.C. 1999. Depositional environment and fossil biota of a thin clastic unit of the Kiowa Formation, Lower Cretaceous (Albian), McPherson County, Kansas. Unpublished MS Thesis, Fort Hays State University, Hays, KS, 97 p. (oldest reported Cretaceous turtle remains in Kansas)
Brinkman, D., Hart, M., Jamniczky, H., and Colbert, M. 2006. Nicholisemys baieri gen. et sp. nov, a primitive chelonioid turtle from the late Campanian of North America. Paludicola 5(4):111-124.
M.H. 2007. Taxonomic comparison and stratigraphic distribution of Toxochelys
(Testudines: Cheloniidae) of
Case, E.C. 1897. On the osteology and relationship of Protostega. Journal of Morphology 14:21-60, pl. 4-6.
Case, E.C. 1898. Toxochelys. The University Geological Survey of Kansas, Part IV. 4:370-385. pls. 79-84.
Cope, E.D. 1870. Observations on the Reptilia of the Triassic formations of the Atlantic regions of the United States. Proceedings of the American Philosophical Society 11(84):444-446. (includes the description of Pneumatoarthrus peloreus, senior synonym of Archelon, Wieland 1896)
Cope, E.D. 1872. [Sketch of an expedition in the valley of the Smoky Hill River in Kansas]. Proceedings of the American Philosophical Society 12(87):174-176. (meeting of October 20, 1871)
Cope, E.D. 1872. On a new Testudinate from the chalk of Kansas. Proceedings of the American Philosophical Society 12(88):308-310. (Cyanocercus incisus )
Cope, E.D. 1872. A description of the genus Protostega, a form of extinct Testudinata. Proceedings of the American Philosophical Society 12(88):422-433. (March 1, 1872)
Cope, E.D. 1872. On the geology and paleontology of the Cretaceous strata of Kansas. Annual Report of the U. S. Geological Survey of the Territories 5:318-349 (Report for 1871).
Cope, E.D. 1872. [On a species of Clidastes and Plesiosaurus gulo Cope]. Proceedings of the Academy of Natural Sciences of Philadelphia 29:127-124
Cope, E.D. 1873. [On Toxochelys latiremis]. Proceedings of the Academy of Natural Sciences of Philadelphia 25:10.
Cope, E.D. 1875. The Vertebrata of the Cretaceous formations of the West. Report, U. S. Geological Survey Territories (Hayden). 2:302 p, 57 pls.
Cope, E.D. 1877. On some new or little known reptiles and fishes of the Cretaceous of Kansas. Proceedings of the American Philosophical Society 17(100):176-181. (Toxochelys latiremis Cope: issue of May-Dec., 1877, printed Nov. 20, 1877)
Derstler, K. 1994. Evolutionary history of sea turtles. Journal of Vertebrate Paleontology 15(suppl. to no. 3):23A.
Derstler, K., A. D. Leitch, P. L. Larson, C. Finsley and L. Hill, 1993. The world's largest turtles - The Vienna Archelon (4.6 m) and the Dallas Protostega (4.2 m), upper Cretaceous of South Dakota and Texas. Journal of Vertebrate Paleont. 13(suppl. to no. 3):33A.
Dollo, L. 1887. Le hainosaure et les nouveaux vertébrés
fossiles du Musée de Bruxelles. Revue des Questions Scienfiques XXI 504-539.
Dollo, L. 1887. Le hainosaure et les nouveaux vertébrés fossiles du Musée de Bruxelles. Revue des Questions Scienfiques XXII 70-112. (July 1887)
Druckenmiller, P.S., Daun, A.J., Skulan, J.L. and Pladziewicz, J.C. 1993. Stomach contents in the upper Cretaceous shark Squalicorax falcatus. Journal of Vertebrate Paleontology. 13(supplement. to no. 3):33A.
D.K., Irby, G.V. and Hutchinson, J.H. 1997. Desmatochelys lowi, a marine
turtle from the Upper Cretaceous. pp. 243-258 in Callaway, J.M. and Nicholls,
E.L. (eds.). Ancient Marine Reptiles, Academic Press, San Diego.
Everhart, M.J. and Pearson, G. 2008. First report on a marine turtle from the Fairport Chalk Member of the Carlile Shale of Mitchell County, Kansas. Kansas Academy of Science, Transactions 112(1-2):138-139 (Abstract).
Gudger, E.W. 1949. Natural history notes on tiger sharks, Galeocerdo tigrinis, caught in Key West, Florida with emphasis on food and feeding habits. Copeia 1949: 39-47, pl. 1-2.
Hay, O.P. 1895. On certain portions of the skeleton of Protostega gigas Cope. Publications of the Field Columbian Museum, Zoological Series (later Fieldiana: Zoology) 1(2):57-62, pls. 4 & 5.
Hay, O.P. 1896. On the skeleton of Toxochelys latiremis. Publ. Field Columbian Museum, Zoological Ser. (later Fieldiana: Zoology), 1(5):101-106, pls. 14 &15.
Hay, O.P. 1905. A revision of the species of the family of the fossil turtles called Toxochelyidae with descriptions of two new species of Toxochelys and a new species of Porthochelys. American Museum of Natural History Bulletin 21(10):177-185.
Hay, O.P. 1908. The fossil turtles of North America. Carnegie Institution of Washington, Publication No. 75, 568 pp, 113 pl.
Hirayama, R. 1994. Phylogenetic systematics of chelonioid sea turtles. The Island Arc 3:270-284.
Hirayama, R. 1997. Distribution and diversity of Cretaceous cheloniids. pp. 225-241 in Callaway, J.M. and Nicholls, E.L. (eds.), Ancient Marine Reptiles, Academic Press, San Diego.
Holder, C.F. 1885.
Monster sea-turtle found in Kansas. Kansas City Review of Science and Industry
Hooks, G.E., III. 1998. Systematic revision of the Protostegidae, with a redescription of Carcarichelys gemma Zangerl, 1957. Journal of Vertebrate Paleontology, 18(1):85-98.
Kear, B.P. 2006.
First gut contents in a Cretaceous sea turtle. Biological Letters 2:113-115.
Konuki, R. 2008.
Biostratigraphy of sea turtles and possible bite marks on a Toxochelys (Testudine,
Chelonioidea) from the Niobrara Formation (Late Santonian),
Lane, H.H. 1946, A survey of the fossil vertebrates of Kansas, Part III, The Reptiles, Kansas Academy Science, Transactions 49(3):289-332, 7 figs.
Lehman, T.M. and Tomlinson, S.L. 2004. Terlinguachelys
fischbecki, a new species of sea turtle (Chelonioidea: Protostegidae) from
the Upper Cretaceous of Texas. Journal of Paleontology 78(6):1163-178.
Leidy, J. 1865. Cretaceous reptiles of the United States. Smithsonian Contributions to Knowledge 14(192):1-135, pls. 1-20.
Manning, E.M. 1994. Dr. William Spillman (1806-1886), pioneer paleontologist of Mississippi. Mississippi Geology. 15(4):64-69.
Matzke, A.T. 2007. An almost complete juvenile
specimen of the cheloniid turtle Ctenochelys stenoporus (Hay, 1905) from
the Upper Cretaceous Niobrara Formation of
Matzke, A.T. 2009. Osteology of the skull of Toxochelys (Testudines, Chelonioidea) (with 25 text-figures). Palaeontographica Abteilung A 288(4):93-150.
Moodie, R.L. 1908, The relationship of the turtles and plesiosaurs, Kansas University Science Bulletin, 4(15):319-32.
Mulder, E.W.A. 2003. On latest Cretaceous tetrapods from the Maastrichtian type area. Publicaties van het Natuurhistorisch Genootshap in Limburg, Reeks XLIV, aflevering 1.Stichting Natuurpublicaties Limburg, Maastricht.
Nicholls, E.L. 1988. New material of Toxochelys latiremis Cope, and a revision of the genus Toxochelys (Testudines, Chelonoidea). Journal of Vertebrate Paleontology, 8(2):181-187.
Nicholls, E.L. 1992. Note on the occurrence of the marine turtle Desmatochelys (Reptilia: Chelonioidea) from the Upper Cretaceous of Vancouver Island. Canadian Journal of Earth Sciences 29:377-380.
Nicholls, E.L., Tokaryk, T.T. and Hills, L.V. 1990. Cretaceous marine turtles from the Western Interior Seaway of Canada. Canadian Journal Earth Sciences 27:1288-1298.
H.F. 1904. Field expeditions during the past season. Science N.S. 19(470):35-36.
Parmenter, C.S. 1899. Fossil turtle cast from the Dakota epoch. Kansas Academy of Science, Transactions 16:67.
Parris, D.C., DeTample, C. and Benton, R.C. 1986. Osteological notes on the fossil turtle ?Dollochelys atlantica (Zangerl). The Mosasaur 3:97-108.
Renger, J.J. 1935. Excavation of Cretaceous reptiles in Alabama. Science Monthly 41:560-565.
Roth, D.D. and Everhart, M.J. 2012. Preparation of a protostegid turtle from the Fairport Chalk (Carlile Formation, Late Cretaceous). Kansas Academy of Science, Transactions 115(1-2):71-72.
Rothschild, B.M. 1987. Decompression syndrome in fossil marine turtles. Annals of Carnegie Museum 56(15):253-258.
Russell, D.A. 1993. Vertebrates in the Western Interior Sea. Pages 665-680 in Caldwell, W. G. E. and E. G. Kaufmann, eds., Evolution of the Western Interior Basin, Geological Association of Canada. Special Paper 39.
Shimada, K., Everhart, M.J. and Hooks, G.E. 2002. Ichthyodectid fish and protostegid turtle bitten by the Late Cretaceous lamniform shark, Cretoxyrhina mantelli. Journal of Vertebrate Paleontology 22(supplement. to 3):106A. (Abstract)
Sternberg, C.H. 1884. Directions for collecting vertebrate fossils. Kansas City Review of Science and Industry 8(4):219-221.
Sternberg, C.H. 1899. The first great roof. Popular Science News 33:126-127, 1 fig.
Sternberg, C.H. 1905. Protostega gigas and other Cretaceous reptiles and fishes from the Kansas chalk. Kansas Academy Science, Transactions 19:123-128.
Sternberg, C.H. 1906. Some animals discovered in the fossil beds of Kansas. Kansas Academy of Science, Transactions 20:122-124.
Sternberg, C.H. 1907. My expedition to the Kansas Chalk for 1907. Kansas Academy of Science, Transactions 21:111-114.
Stewart, J.D. 1978. Earliest record of the Toxochelyidae. Kansas Academy of Science, Transactions 81(2):178 (abstract).
Stewart, J.D. 1990. Niobrara Formation vertebrate stratigraphy, pages 19-30, In Bennett, S. C. (ed.), Niobrara Chalk Excursion Guidebook, The University of Kansas Museum of Natural History and the Kansas Geological Survey.
Wagner, G. 1898. On some turtle remains from the Fort Pierre. Kansas University Quarterly 7(4):201-203.
Wieland, G.R. 1896. Archelon ischyros: a new gigantic cryptodire testudinate from the Fort Pierre Cretaceous of South Dakota. American Journal of Science, 4th Series 2(12):399-412, pl. v.
Wieland, G.R. 1900. Some observations on certain well-marked stages in the evolution of the testudinate humerus. American Journal of Science, 4th Series, 9(54):413-424, with 23 text fig.
Wieland, G.R. 1902. Notes on the Cretaceous turtles, Toxochelys and Archelon, with a classification of the marine Testudinata. American Journal of Science, Series 4, 14:95-108, 2 text-figs.
Wieland, G.R. 1905. A new Niobrara Toxochelys. American Journal of Science 20(119):325-343, pl. X, 8 text-figs.
Wieland, G.R. 1906. The osteology of Protostega, Memoirs of the Carnegie Museum, 2(7):279-305.
Wieland, G.R. 1909. Revision of the Protostegidae. American Journal of Science, Series 4. 27(158):101-130, pls. II-IV, 12 text-figs.
Williston, S.W. 1894. A new turtle from the Benton Cretaceous. Kansas. University Quarterly 3(1):5-18, with pl. II-VI.
Williston, S. W. 1898. Turtles. The University Geological Survey of Kansas, Part VI. 4:349-369. pls. 73-78.
Williston, S.W. 1901. A new turtle from the Kansas Cretaceous. Kansas Academy Science, Transactions 17:195-199.
Williston, S.W. 1902. On the hind limb of Protostega. American Journal of Science, Series 4, 13(76):276-278, 1 fig.
Williston, S.W. 1914. Water reptiles of the past and present. Chicago University Press. 251 pp.
Zangerl, R. 1953. The vertebrate fauna of the Selma formation of Alabama, Part IV, the turtles of the family Toxochelyidae. Fieldiana (Geology Memoirs): 3(4): 137 - 277.
Zangerl, R. 1980. Patterns of phylogenic differentiation in the toxochelyid and chelonid sea turtles. American Zoologist 20:585-596.
Zangerl, R. and R.E. Sloan. 1960. A new description of Desmatochelys lowi (Williston). A primitive cheloniid sea turtle from the Cretaceous of South Dakota. Fieldiana, Geology Memoirs 14:7-40.