A shell-crushing shark from the Late Cretaceous of western Kansas.
Copyright © 2000-2012 by Mike Everhart
Last updated 12/10/2012
LEFT: FHSM VP-14785 - an upside down upper Ptychodus mortoni jaw plate as found, Smoky Hill Chalk, Gove County, Kansas.
|Ptychodus is a genus of durophagous (shell-crushing)
sharks from the Late Cretaceous. Their teeth are often found as fossils around the
world. They are also fairly common occurrences in the sediments deposited in the Western Interior Sea of North America.
They became extinct in the Western Interior Sea during the Santonian, about 85 million years ago.
LEFT and RIGHT: Associated upper and lower jaw plates of Ptychodus mortoni collected from middle Smoky Hill Chalk Gove Co., Kansas, and prepared by Dennis Olson.
When Ptychodus remains were first discovered in England, they were generally recognized as being the “palates of fish.” One of the first references that I can find, pages 408-409 in Urban, S. (ed., August, 1755) mentions "specimens of fossil palates of fishes, collected from under the northern cliffs of Shepey Island.” The illustrations accompanying the note do not appear to represent Ptychodus teeth, but the terminology seems to begin about that time. Bright, (1817) in describing the geology near Bristol, England, wrote “16. A thin bed of limestone breccia containing rounded pebbles, and organized substances resembling palates of fish.” Conybeare and Phillips (1822) describe the “Vertebrae of fish, Sharks teeth, and many singular palatal tritores, and the radius of a Balistes, exhibit proofs of the existence of vertebral animals in this formation.”
|LEFT: Some of the first illustrations of Ptychodus
teeth (as yet unnamed at the time) was in Mantell (1822). On page 231,
Mantell remarked, “But the fossil teeth
are sometimes found in considerable numbers, and of various sizes,
forming a tesselated surface of
several square inches; and so regularly disposed, the smaller palates
being adapted to the intervals between the larger ones, that no doubt can
exist of this having been the mode in which they were placed in the
original. Hence, instead of each specimen being. a distinct palate, like
the corresponding teeth of the Diodon, they appear to have
constituted the covering of the entire roof and base of the mouth.
These teeth are termed by Mr. Miller, dentes tritores: "they differ from the molares, in not being affixed to the jaws." He supposes them "to have been attached to the palate bones, os hyoides, &c. of fish of the genera Diodon, and Balistes. It was their office to crush the food, fishes generally having teeth of detention in their maxillæ."
Mantell (1829, page 207) wrote “the palates resemble those of Diodon
Histrix; but from the numbers often found grouped together, the mouth
of the original appears to have been paved with them.”
|LEFT: Mantell (1833): The
fossil palate teeth have hitherto been considered as belonging to a fish
related to the Diodon; they are more or less of a quadrangular shape,
having the outer surface convex, and composed of an exceedingly hard
enamel, which in the centre is formed into sharp and slightly curved
ridges; these are surrounded by a border of obtuse papillae. The Diodon
histrix has one tooth of this kind affixed to the os hyoides, and
another to the palate or roof of the mouth. But the fossil teeth are
sometimes found in considerable numbers, and of various sizes, forming a
tesselated surface of several square inches; and so regularly disposed,
the smaller palates being adapted to the intervals between the larger
ones, that no doubt can exist of this having been the mode in which they
were placed in the original. Hence, instead of each specimen being a
distinct palate, like the corresponding teeth of the Diodon, they appear
to have constituted the covering of the entire roof and base of the mouth.
|Morton (1834, p. 30) wrote: "In the Academy of Natural Sciences, and in
private collections in this city, are some interesting remains which
have belonged to Saurian animals. I possess some singular specimens
figured on pl. xviii., figs. 1 and 2. At first I supposed them to be
dermal bones, allied to those of the Hylæosaurus,
as figured by Mr. Mantell; but as they possess a distinct enamel, and as
some specimens are worn by attrition on the apex, they may have been the palate
bones of some marine animal."
LEFT: The first illustration of a Ptychodus mortoni tooth was published by Morton (1834) but was not further identified in the caption other than "The palate bones of a Fish?"
|The same specimen was later sent to Dr. Mantell in England for
identification. It was subsequently named by Mantell - "I have named it
Ptychodus Mortoni" (1836, p. 27). The
specimen is now in the British Museum of Natural History (Mantell
Collection - BMNH 28394)
According to Morton (1842, p. 215), the first tooth of Ptychodus mortoni was found by "Mr. Conrad in the older cretaceous strata at Prairie Bluff, Alabama." (Manning (Pers. comm, 2002) indicated that is more likely that the tooth was from the Mooreville Chalk near Erie, Alabama). Morton also noted that “I subsequently sent specimens of them to my distinguished friend, Dr. Mantell, who returned me three beautiful drawings (which are accurately copied on the annexed plate), with the name Ptychodus Mortoni appended. Dr. Mantell, however, has not informed my in what work the descriptions is published.”
Mantell apparently sent Agassiz’s drawing to Morton without
informing Morton of his 1836 publication, or the source of the drawings.
LEFT: Ptychodus mortoni described and figured by
Agassiz (1836, Vol. 3, p. 158, pl. 25, fig. 1-3). The original description by Agassiz is
included below. Roughly translated, Agassiz wrote: I
saw in the collection of Mr. Mantell a very similar tooth in form to those of Ptychodus
in general but in which differs by the provision of the folds of its surface. Instead of
large simple transverse wrinkles, the crown presents large ramified folds being born from
the most projecting part of the tooth (fig. 3), and attenuating imperceptibly towards the
horizontal pad which separates the crown from the root (fig. 1 and 2). Having seen up to
now only one tooth of this species, I cannot affirm if the provision of its folds, the
height of its crown and the width of its base are specific characters, or if these details
vary in different positions in the mouth. This tooth comes from the green sand of the
The plate published by Agassiz (below) a year later was color):
VI.PTYCHODUS MORTONI Ag.
Vol. 3, Tab. 25, fig. 1, 2 et
Jai vu dans la collection de M.
Mantell une dent très-semblable, par sa
forme, à celles des Ptychodus en général
mais qui en deffère par la disposition des plis de sa surface. Au lieu de grosses rides tranversales simples, la couronne
présente de gros plis ramifiés, naissant de la partie la plus saillante de
la dent fig. 3, et satténuant insensiblement
vers le bourrelet horizontal qui sépare la
couronne de la ricine, fig. 1 et 2. Nayant vu jusquici quune seule dent de cette espèce, je
ne puis affirmer si la disposition de ses plis, la hauteur
de sa couronne et la largeur
de sa base sont des caractères spécifiques, ou si
ces détails varient sur différens points de la gueule.
|In a note on Ptychodus (1873 p. 295), Leidy wrote, "The
extinct genus of cestraciont fishes above named was inferred by Agassiz, from isolated
teeth, the only parts yet found which can be with any certainty referred to the same
animal. A number of species have been indicated, mostly by the same authority, from the
specimens found in the Cretaceous formations of Europe and America."
Teeth of Ptychodus Mortoni have been discovered in the Cretaceous deposits of Alabama, Mississippi, and Kansas, but I have seen none from the corresponding formation of New Jersey or elsewhere. "
LEFT: Jean Louis Rudolph Agassiz (1807-1873) - Swiss born scientist and paleontologist and one of the founders of the Museum of Comparative Zoology at Harvard, Agassiz described and named most of the species of fossil sharks that we are familiar with today. (Agassiz, J. L. R. 1833-1844. Recherches sur les Poissons Fossiles. 3: pp. vii + 390 + 32, Neuchàtel and Soleure)
|LEFT: I was fortunate enough to find an articulated specimen of this species of "shell-crushing" shark (Ptychodus mortoni) while collecting mosasaur remains in December of 1991 in Gove County, Kansas. It consists of more than 100 (mostly) articulated teeth. As shown above, the upper jaw was lying on the surface of the chalk, crown-side down when discovered. The specimen was in the process of coming apart as it eroded out. The jaw plate was found between Hattin's (1982) Marker Unit 4 and Marker Unit 5, and are late Coniacian in age (about 86 mya). This specimen was been donated (2002) to the Sternberg Museum of Natural History and is curated as FHSM VP-14785. The specimen is fully described in Shimada 2012.|
|LEFT: An artist's conception of what Ptychodus mortoni may have looked like... based on the modern Port Jackson Shark (Heterodontus -See Systematic Paleontology section below). This painting is part of a mural at the Sternberg Museum of Natural History in Hays, Kansas. .|
Ptychodus mortoni is one of four ptychodontid species documented from the Smoky Hill Chalk Member of the Niobrara Chalk Formation (P. anonymous (now P. rugosus per Hamm, 2010), P. latissimus, P. polygyrus and P. martini are the other four). From the number of single teeth and other remains that have been found, P. mortoni apparently was the most common species at this time, and probably the last species of Ptychodus to be found in the Western Interior Sea. P. mortoni became extinct in the Western Interior Sea about the 85 million years ago in the middle Santonian. No one is quite sure what they looked like, but from the shark-like vertebrae associated with several specimens, it appears that they may have been more shark-like in body form than ray-like. Judging from the size of some isolated teeth and this specimen of 539 associated teeth (KUVP 55270) in the University of Kansas Museum of Natural History collection, these fish probably grew to lengths of 4-5 meters (See Shimada, et al. 2010 for an even larger estimate). Here are some representative (and very worn) teeth from a specimen in the Sternberg Museum of Natural History that includes over 870 teeth (FHSM VP-335).
Dr. G.M. Sternberg and Professor B.F. Mudge) were among the first to collect Ptychodus teeth from the Smoky Hill Chalk. Mudge's contribution was acknowledged by Cope (1874) while Sternberg was credited by Leidy (1873), including several specimens that he illustrated. In regard to the Ptychodus mortoni teeth, Leidy noted that. "The Smithsonian Institution has submitted to my examination a collection of fourteen specimens of teeth obtained by Dr. George M. Sternberg, United States Army, from the banks of Chalk Bluff Creek, a branch of Smoky Hill River, about sixty miles east of Fort Wallace, Kansas. The specimens were found in two parcels, each together, as if pertaining to two individuals." The figures published by Leidy are shown below:
|Ptychodus mortoni Agassiz 1836, from two individuals,
collected by Dr. George M. Sternberg in 1867.
Leidy, Joseph, 1873. Contributions to the extinct vertebrate fauna of the western interior territories. Rept., U.S. Geol. Surv. Terr. (Hayden) 1:358 pp., 37 pls.
|LEFT: A reconstruction of the lower jaws (Meckel's cartilages) of a young Ptychodus decurrens specimen from the English Chalk by A.S. Woodward (1904).|
|LEFT: Three of 876 Ptychodus mortoni teeth from a single
specimen (FHSM VP-335). Collected from Hells Bar Canyon in southwest Gove County in 1952.
Note the wear facet on the large tooth at far left.
RIGHT: Three of 112 teeth of a single specimen of Ptychodus mortoni (FHSM VP-336) from the same locality as above. This locality represents the last occurrence of Ptychodus in the Smoky Hill Chalk (Just below Hattin's Marker Unit 10, Middle Santonian).
Below are pictures of the Ptychodus mortoni specimen (FHSM VP-14785) that I collected and donated to the Sternberg Museum of Natural History:
|Crown view of the FHSM VP-14785 Ptychodus mortoni tooth
sets (old EPC 1991-106). The round object at the lower left
is a small Platyceramus sp. shell that
is probably within the size range of prey preferred by ptychodontid sharks.
Here is a view of a partial tooth plate in the Sternberg Museum of Natural History (FHSM VP-2238). Note that this picture shows the probably full width of the jaw plate sets. The anterior and posterior portions are missing.
|Root view of the above specimen. Note the row of small symphysial teeth between the two medial tooth rows. Ptychodus teeth are found at the same stratigraphic levels as compacted masses of crushed, very thin (less than .3 mm) Inoceramid shells..... Are these Ptychodus coprolites?... I think so. It is more likely that even the larger ptychodontid sharks preferred the small, thin-shelled juvenile inoceramids to the much larger, thicker shelled adults.|
|A close-up of several of the teeth in one of the FHSM VP-14785 tooth sets, showing wear on the apex of each tooth that might be expected if they were used to crush hard objects.|
|Another close-up, from an angle.|
|Another close-up. Note that, unlike most Ptychodus teeth, the ridges radiate from a center point in Ptychodus mortoni, not like the parallel ridges in P. anonymus or P. martini.|
|A picture of 20 articulated teeth near the center of the FHSM VP-14785 specimen.|
|A view of the medial rows of teeth, showing portions of the tops of the symphysial teeth (small teeth between the larger top and middle rows).|
|One of the unusual features of this specimen is the 'roll-over' of teeth at the back of the right side of the jaw plate... In the case of Ptychodus, the new teeth were formed under the back of the jaw plate and moved over the edge as the roots were added. There are five teeth in the process of being formed under the jaw plate in this area.|
|This is a picture of the lower or root side of the jaw plate, showing the incomplete root of a single forming (bud) tooth that had been preserved below the articulated teeth in the tooth plate.|
Class Chondrichthyes Huxley, 1880
Subclass Elasmobranchii Bonaparte, 1838
Cohort Euselachii Hay, 1902
Subcohort Neoselachii Compagno 1977
Order incertae sedis
Family Ptychodontidae Jaekel, 1898
Genus Ptychodus Agassiz, 1835
Ptychodus mortoni Agassiz 1836
"Woodward (1887, p. 128) noted that the dentition of Ptychodus is that of a true Ray, and does not bear the slightest resemblance to that of the Cestraciont Sharks. While the Family Ptychodontidae has more recently been included in the Superfamily Hybodontoidea Zangerl, 1981 (Cappetta, 1987; Welton and Farish, 1993, and others), Stewart (1980) suggested that that all living sharks and rays (including Heterodontus) are members of the monophyletic Neoselachii, united by synapomorphies including the presence of calcified centra. Since Ptychodus shares this derived state, it must be regarded as a neoselachian and not as a hybodont
Stewarts conclusion was based on calcified centra found in a relatively complete specimen Ptychodus mortoni which is now in the University of Kansas collection (KUVP 59041). Cappetta (1987, p. 37) acknowledged Stewarts comments, but noted that it cannot be excluded that calcified centra appeared parallely in very specialized hybodonts like Ptychodus.
Unfortunately, KUVP 59041 has not been described further. Stewarts (1980) suggestion is followed here while the authors note that additional refinement is necessary regarding the placement of the Family Ptychodontidae within the Neoselachii." (From Everhart and Caggiano 2004)
A recent discovery..................On June 1, 2003, while we were surveying a new locality, my wife (Pam) found another Ptychodus mortoni specimen coming out from under a small bush. The specimen was donated to the Sternberg Museum and is curated as FHSM VP-15532.
|We could see about 20 teeth lying on the surface, some of which were obviously scattered away from the main area. It had rained recently and it was apparent that a lot of water and surface debris had flowed across the specimen. I picked up about 10 teeth in a small gully below the place where the teeth had eroded out, and looked around to see if there were any more. Once I had bagged the loose teeth, I began to try to locate the source. I soon found that most of the teeth were still in the chalk. The count was up to about 150 by the time I finished digging around the bush. I collected the matrix and then water-washed it after we returned home. There were about 55 more teeth still in the matrix, mostly very small laterals , giving a total count of about 205 for this specimen.|
|LEFT: A 2009 reconstruction of the VP-15532 jaw plate by
Shawn Hamm. It turned out to portions of both the upper and lower
RIGHT: A new (2010) upper jaw plate from the Smoky Hill Chalk of Logan County, KS. This specimen (FHSM VP-17606), discovered by Steve Mense, included more than 550 teeth, pieces of the upper jaw (palatoquadrate), two vertebrae, and hundreds of tiny dermal and oral denticles. The jaw plate, as reconstructed at right, measures 20 inches wide by 22 inches long, but would have been somewhat smaller in life.
Suggested references on Ptychodus in Kansas and around the world:
Agassiz. L. 1835. Feuilleton additionel sur les Recherches sur les Poissons fossiles.
Agassiz, L. 1836. Recherches sur les Poissons Fossiles. 3: pp. vii + 390 + 32, Neuchàtel.
Applegate, S. P. 1970. The vertebrate fauna of the Selma Formation of Alabama; Part VIII, The Fishes. Fieldiana Geology Memoirs 3(8):383-433, text figs. 174-204.
Bright, R. 1817. VIII. On the Strata in the Neighourhood of Bristol. Transactions of the Geological Society 4:193-205. (Read 15 November, 1811).
Cappetta, H. 1973. Selachians from the Carlile Shale (Turonian) of South Dakota. Journal of Paleontology 47(3):504-514.
Cappetta, H. 1987. Chondrichthyes II - Mesozoic and Cenozoic Elasmobranchii. Gustav Fischer Verlag, Stuttgart and New York. 193 p., 148 fig.
Case, G. R. and D. R. Schwimmer. 1988. Late Cretaceous fish from the Blufftown Formation (Campanian) in western Georgia. Journal of Paleontology 62(2):290-301.
Case, G. R., T. T. Tokaryk and D. Baird. 1990. Selachians from the Niobrara Formation of the Upper Cretaceous (Coniacian) of Carrot River, Saskatchewan, Canada. Canadian Journal of Earth Sciences 27:1084-1094.
ON LINE: Cicimurri, D. 2001. Cretaceous elasmobranchs of the Greenhorn Formation (Middle Cenomanian-Middle Turonian), western South Dakota. p. 27-43 in V. L. Santucci and L. McClelland (eds.), Proceedings of the Sixth Fossil Resource Conference, Geologic Resources Division Technical Report, NPS/NRGRD/GRDTR-01/01.
Cicimurri, D. J. 2004. Late Cretaceous chondrichthyans from the Carlile Shale (Middle Turonian to Early Coniacian) of the Black Hills region, South Dakota and Wyoming. The Mountain Geologist 41(1):1-16.
Conybeare, W.D. and Phillips, W. 1822. Outlines of the Geology of England and Wales. Book III, Chapter I. Section IV. Carboniferious or Mountain Limestone. Page 356
Cope, E. D. 1874. Review of the Vertebrata of the Cretaceous period found west of the Mississippi River. U. S. Geological and Geographical Survey of the Territories, Bulletin 1(2):3-48.
Cope, E. D. 1875. The Vertebrata of the Cretaceous formations of the West. Report of the U. S. Geological Survey of the Territories (Hayden). 2:302 pp., 57 pls.
David, M.L. 1996. Dental histology of Ptychodus and its implications in the phylogeny of the Ptychodontidae, Journal of Vertebrate Paleontology 16(suppl. to 3):30A.
David, M.L. 1999. A histological and mechanical description of Ptychodus. M.S. thesis, Fort Hays State University, Hays, Kansas, 44 pp.
DeKay, J.E. 1842. Part IV, Fishes, 415 pp, Pl. LXXIX, (Ptychodus mortoni Mantell, p. 386)
Dibley, G. E. 1911. On the teeth of Ptychodus and their distribution the English Chalk. Quarterly Journal of the Geological Society of London 67:263-277, pls. 17-22.
Dixon, F. 1850. The geology and fossils of the Tertiary and Cretaceous formations of Sussex.
Everhart, M. J. 2003. First records of plesiosaurs from the lower Smoky Hill Chalk Member (Upper Coniacian) of the Niobrara Formation of western Kansas. Kansas Academy of Science, Transactions 106(3-4):139-148.
Everhart, M. J. and Caggiano, T. 2004. An associated dentition and calcified vertebral centra of the Late Cretaceous elasmobranch, Ptychodus anonymus Williston 1900. Paludicola 4(4), p. 125-136.
Everhart, M. J., T. Caggiano, and K. Shimada. 2003. Note on the occurrence of five species of ptychodontid sharks from a single locality in the Smoky Hill Chalk (Late Cretaceous) of western Kansas. (Abstract) Kansas Academy of Science, Transactions 22:29.
Everhart, M. J. and Darnell. M.K. 2004. Occurrence of Ptychodus mammillaris (Elasmobranchii) in the Fairport Chalk Member of the Carlile Shale (Upper Cretaceous) of Ellis County, Kansas. Kansas Academy of Science, Transactions 107(3-4):126-130.
Evetts, M. J. 1979. Upper Cretaceous sharks from the Black Hills region, Wyoming and South Dakota. The Mountain Geologist, 16(2):59-66.
Gibbes, R. W., 1848. Monograph of the fossil Squalidae of the United States. Jour. Acad. Nat. Sci. Phila. Vol. 1, 2nd Ser., pt. 2, art. 12:139-147. pls. 18-21 (Ptychodus polygyrus).
Hamm, S. A. and M. J. Everhart. 1999. The occurrence of a rare ptychodid shark from the Smoky Hill Chalk (Upper Cretaceous) of western Kansas. Kansas Academy of Science, Transactions (Abstracts) 18:34.
Hamm, S. A. and K. Shimada. 2002. Associated tooth set of the Late Cretaceous lamniform shark, Scapanorhynchus raphiodon (Mitsukurinidae), from the Niobrara Chalk of western Kansas. Kansas Academy of Science, Transactions 105(1-2):18-26. Hattin, D. E. 1982. Stratigraphy and depositional environment of the Smoky Hill Chalk Member, Niobrara Chalk (Upper Cretaceous) of the type area, western Kansas. Kansas Geological Survey Bulletin 225:108 pp.
Herman, J. 1977. Les sélaciens des terrains néocrétacés et paléocenes de Belgique et des contrées limitrophes. Eléments dune biostratigraphique inter-continentale. Mémoires pour sérvir a l'explication des Cartes géologiques et miniéres de la Belgique. Service Géoligique de Belgique, Mémoire 15, 401 pp.
Kauffman, E. G. 1972. Ptychodus predation upon a Cretaceous Inoceramus. Journal of Paleontology 15(3):439-444.
Leidy, J. 1868. Notice of American species of Ptychodus. Proceedings of the Academy of Natural Sciences of Philadelphia 20:205-208.
Leidy, J. 1873. Contributions to the extinct vertebrate fauna of the western territories. Report of the U.S. Geological Survey of the Territories (Hayden), 1:358 pp., 37 pls.
Lucas, S. G., B. S. Kues, S. N. Hayden, B. D. Allen, K. K. Kietzke, T. E. Williamson, P. Sealy, and R. Pence. 1988. Cretaceous stratigraphy and biostratigraphy, Cookes Range, Luna County, New Mexico. New Mexico Geological Society Guidebook, 39th Field Conference 143-167.
MacLeod, N. and B. H. Slaughter. 1980. A new ptychodontid shark from the Upper Cretaceous of northeast Texas. The Texas Journal of Science 32(4):333-335.
MacLeod, N. 1982. The first North American occurrence of the Late Cretaceous elasmobranch Ptychodus rugosus Dixon with comments on the functional morphology of the dentition and dermal denticles. Journal of Paleontology 56(2): 520-524.
Manning, E. M. and D. T. Dockery III. 1992. A guide to the Frankstown vertebrate fossil locality (Upper Cretaceous), Prentiss County, Mississippi. Mississippi Department Environmental Quality, Office of Geology Circular 4:43 pp., 2 pl.
Mantell, G. 1822. Fossils of the South Downs, or, Illustrations of the geology of Sussex. Lupton Relfe, London, 320 pp., Plates I-XLII
Mantell, G.A. 1827. Illustrations of the Geology of Sussex. Lupton Reefe, London, 92 pp, 20 plates.
Mantell, G. 1829. A Tabular Arrangement of the Organic Remains of the County of Sussex. Transactions of the Geological Society of London 2-3:201-216. Page 207
Mantell, G. 1833. The Geology of the South-East of England. Longman, Rees, Orme, Brown & Longman, London, 415 pp., Pl. I-V, Map.
Mantell, G. 1836. A Descriptive Catalogue of the Objects of Geology, Natural History, and Antiquity (chiefly discovered in Sussex,) in the Museum attached to the Sussex Scientific and Literary Institution at Brighton. Relfe and Fletcher, London., 41 pp
Meyer, R. L. 1974. Late Cretaceous elasmobranchs from the Mississippi and east Texas embayments of the Gulf Coastal Plain. Unpublished doctoral dissertation, Southern Methodist University, Dallas, 400pp.
Morton, S. G., 1834. Synopsis of the organic remains of the Cretaceous group of the United States. Key and Biddle, Philadelphia, 88 pp., 19 pl.
Morton, S. G. 1842. Description of some new species of organic remains of the Cretaceous group of the United States; with a tabular view of the fossils hitherto discovered in this formation. Journal of the Academy of Natural Sciences of Philadelphia. 8:207-227, 2 pl.
Mudge, B. F. 1876. Notes on the Tertiary and Cretaceous periods of Kansas. Bulletin of the U. S. Geological Survey of the Territories (Hayden), 2(3):211-221.
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.
Parkin, J. A., K. Shimada, and B. A. Schumacher. 2002. Fossil fishes from the lowermost Greenhorn Limestone (Upper Cretaceous: Middle Cenomanian) in southeastern Colorado. Paper No. 187-15, Geological Society of American Annual Meeting.
Schwimmer, D. R., J. D. Stewart and G. D. Williams. 1997. Scavenging by sharks of the genus Squalicorax in the Late Cretaceous of North America. Palaios 12:71-83.
Shimada, K. 1993. Upper Cretaceous elasmobranchs from the Blue Hill Shale Member of the Carlile Shale, Western Kansas. Kansas Academy of Science, Transactions 12(78).
Shimada, K. 1996. Selachians from the Fort Hays Limestone Member of the Niobrara Chalk (Upper Cretaceous), Ellis County, Kansas. Kansas Academy of Science, Transactions 99(1-2):1-15.
Shimada, K. 2012. Dentition of Late Cretaceous shark, Ptychodus mortoni (Elasmobranchii, Ptychodontidae). Journal of Vertebrate Paleontology 32:6:1271-1284.
Shimada, K. and M. J. Everhart. 2003. Ptychodus mammillaris (Elasmobranchii) and Enchodus cf. shumardi (Teleostei) from the Fort Hays Limestone Member of the Niobrara Chalk (Upper Cretaceous) in Ellis County, Kansas. Kansas Academy of Science, Transactions 106(3-4):171-176.
Shimada, K., Everhart,
M.J., Decker, R. and Decker P.D. 2010. A new skeletal remain of the durophagous
shark, Ptychodus mortoni, from the Upper Cretaceous of
Shimada, K. and D. J. Martin. 1993. Upper Cretaceous selachians from the basal Greenhorn Limestone in Russell Co., Kansas. Kansas Academy of Science, Transactions 12:78.
Skelton, L. H. 1996. A brief history of the Kansas Academy of Science. Kansas Academy of Science, Transactions 101(3-4):140-145.
Stewart, J. D. 1980. Reevaluation of the phylogenetic position of the Ptychodontidae. Abstracts of Papers, Kansas Academy of Science, Transactions 83(3):154.
Stewart, J. D. 1988. Paleoecology and the first North American west coast record of the shark genus Ptychodus. Journal of Vertebrate Paleontology, 8:27A.
Stewart, J. D. 1990. Niobrara Formation vertebrate stratigraphy. Pages 19-30, in S. C. Bennett, (ed.), Niobrara Chalk Excursion Guidebook. University of Kansas Museum of Natural History and Kansas Geological Survey.
Urban, S. (ed.). 1755 (August). The Gentleman's Magazine and Historical Chronicle. Volume XXV, pp. 408-409.
Welton, B. J. and R. F. Farish. 1993. The collectors guide to fossil sharks and rays from the Cretaceous of Texas. Horton Printing Company, Dallas, 204 pp.
Williamson, T. E., J. I. Kirkland and S. G. Lucas. 1993. Selachians from the Greenhorn cyclothem ("Middle" Cretaceous: Cenomanian-Turonian), Black Mesa, Arizona, and the paleogeographic distribution of Late Cretaceous selachians. Journal of Paleontology 67(3):447-474.
Williamson, T. E., S. G. Lucas and J. I. Kirkland. 1990. The Cretaceous elasmobranch Ptychodus decurrens Agassiz from North America. Geobios 24(5):595-599.
Williston, S. W. 1900. Cretaceous fishes [of Kansas]. Selachians and Pycnodonts. University Geological Survey Kansas VI pp. 237-256, with pls.
Woodward, A.S. 1887. On the dentition and affinities of the selachian genus Ptychodus Agassiz. Quarterly Journal of the Geological Society 43:121-131, 1 pl.
Woodward, A.S. 1889. Catalogue of the Fossil Fishes of the British Museum (Natural History), Part I containing the Elasmobranchii. London, 474 pp, Pl. I-XVII.
Woodward, A.S. 1904. On the jaws of Ptychodus from the chalk. Quarterly Journal Geological Society London 60:133-136, 1 fig., pl. XV.
LINKS: Ptychodus mortoni - Shell crushing shark from the Smoky Hill Chalk
Earliest Ptychodus mortoni - A shell crushing shark from the basal Fort Hays Limestone.
Sharks teeth by the hundreds - A nearly complete specimen of Ptychodus anonymus from Kansas
Ptychodus sharks teeth from around the world including Ptychodus teeth from the English chalk.
Jim Bourdon's Ptychodus pages - The Life and Times of Long Dead Sharks
NEW - Kansas Sharks - Kansas shark teeth from the Lower Permian through the Upper Cretaceous.
More here on Ptychodus from the English Chalk - Robert Randall's British Chalk Fossils web site
Credits: I thank Earl Manning for our continuing discussion of the history of paleontology in Kansas. and for his contribution of many papers and his notes, including Leidy (1873), and Morton's early papers (1834 / 1842) with the first figures of Ptychodus mortoni teeth.