Ptychodus mortoni   A shell-crushing shark from the Late Cretaceous of western Kansas. Copyright © 2000-2098 by Mike Everhart Last updated 09/07/2009           LEFT: FHSM VP-14785 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, but most often in the sediments deposited in the Western Interior Sea of North America. They became extinct 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.

LEFT: The first illustration of a Ptychodus mortoni tooth was published by Morton (1834) but was not further identified than "The palate bones of a Fish?"

The same specimen was later sent to Dr. Mantell in England for identification. According to Morton (1842), 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. LEFT: Although Morton was the first to publish the name, he did so without a description of the tooth, assuming that Mantell had already done so. The species was officially described and named P. mortoni by Agassiz in 1839 (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 United States, and was communicated to Mr. Mantell by Doctor Morton.” The plate published by Agassiz a year later was color (below):

VI.   PTYCHODUS   MORTONI   Ag. Vol. 3, Tab. 25, fig. 1, 2 et 3.     " J’ai 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 s’atténuant insensiblement vers le bourrelet horizontal qui sépare la couronne de la ricine, fig. 1 et 2. N’ayant vu jusqu’ici qu’une 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.      Cette dent provient du grès vert des États-Unis, et a été communiquée a M. Mantell par le docteur Morton."

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)

I was fortunate enough to find an articulated specimen of this "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 tooth sets were 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 tooth set was found between Hattin's (1982) Marker Unit 4 and Marker Unit 5, and are late Coniacian in age (about 86 mya). This specimen has been donated (2002) to the Sternberg Museum of Natural History and is curated as FHSM VP-14785.

Ptychodus mortoni is one of four ptychodontid species documented from the Smoky Hill Chalk Member of the Niobrara Chalk Formation (P. anonymus, P. latissimus, P. polygyrus and P. martini are the other four). From the number of single teeth and other remains that have been found, it was apparently 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 86 million years ago, near the boundary between the Coniacian and Santonian stages.  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. 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 1839, 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: 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 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).  Here is a view of another pair (partial) of tooth sets in the Sternberg Museum of Natural History (FHSM VP-2238).   Note that this picture shows the probably full width of the tooth sets.  The anterior and posterior portions appear to be missing. 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.
	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 the top 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... apparently the teeth were attached to a surface that was somewhat flexible, at least after the death of the shark, and were folded under the rest of the jaw plate prior to fossilization.   There are five teeth under the jaw plate in this area.
	This is a picture of the lower or root side of the jaw plate, showing the weathered root of a single loose tooth that had been preserved on top of the articulated teeth.

Our newest discovery..................On June 1, 2003, while we were surveying a new locality, my wife (Pam) found another Ptychodus mortoni jaw plate 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.

Suggested references on Ptychodus in Kansas and around the world:

Agassiz, J. L. R. 1833-1844. Recherches sur les Poissons Fossiles. 3: pp. vii + 390 + 32, Neuchàtel and Soleure.

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.

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.

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.

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.

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.

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 d’une 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, 39^th Field Conference 143-167.

Williston, S. W. 1900. Cretaceous fishes [of Kansas]. Selachians and Pycnodonts. University Geological Survey Kansas VI pp. 237-256, with pls.