A new specimen of Ptychodus
Copyright © 2011-2013 by Mike Everhart
Created 10/27/2010 - Last updated 08/19/2013
LEFT: Some of the more than 550 teeth Ptychodus mortoni (FHSM VP-17606) teeth collected in October, 2010, along with calcified cartilage, vertebrae and dermal denticles.
Ptychodus is a extinct genus of durophagous (shell-crushing) sharks from the Late Cretaceous. Their isolated teeth have been collected on all continents, including Australia, but their associated teeth and jaw plates occur most often in the Smoky Hill Chalk deposited in the Western Interior Sea of North America. As a group, Ptychodontids became extinct during the middle Santonian of the Western Interior Sea around 85 million years ago, but they persisted along the Gulf Coast and elsewhere into the early Campanian.
|In October, 2010, I was contacted by Steve Mense, an amateur
collector who had discovered a large number of Ptychodus mortoni
teeth near the Smoky Hill River in eastern Logan County, Kansas. He had
already collected over 300 teeth but needed help in recovering the rest of
the specimen, so we made arrangements to meet at the locality. When I
arrived, he took me to the site and showed me where the teeth were
emerging from the edge of a gully.
LEFT: This is the edge of the excavation before we started. Some teeth are barely visible in the center of the picture.
RIGHT: After we removed some of the overburden and loose teeth around the edges, we reached an area where the teeth were all jumbled together... and noticed some pieces of cartilage (dark brown). Everything was covered with root mats and powdery gypsum, plus the unusually hard gray chalk was badly fractured... not a good recipe for taking it out in a jacket.
This layer of chalk between Hattin's Marker Unit 8 and 9 is difficult to work with because it is harder than normal and does not come up in nice, flat layers. After trying for a half hour or so to trench around the specimen to get ready it ready for a jacket, it became apparent that all were were doing was damaging it. Although I would have rather put a secure jacket around it, we finally decided to take it up carefully in pieces. As it turned out, nearly all of the large chunks of cartilage came up without breaking. Not pretty but at least we weren't taking the risk of having it fall out of the jacket in pieces when we turned it.
|LEFT: One of the first things I noticed when
I started cleaning up the specimen was the "gritty" feel of just
about everything. On closer look, I could see a mixture of denticles
and cartilage prisms covering many of the teeth, including a portion of
the crown of this medium sized tooth.
RIGHT: This close-up shows a mixture of cartilage prisms and denticles partially covering the crown of the tooth. The denticles are circled. ...There is also a tiny fish vertebra on the far right edge of the photo.
|LEFT: Several micro-photographs of the
denticles discovered on the teeth. Denticles are about 0.5 to 1.5 mm in
RIGHT: These are the most common of the denticles... they are probably "dermal" denticles from the skin of the shark... called shagreen, it is what makes shark skin feel like sand paper.
|LEFT: A close-up of an oral denticles. These
larger denticles line the mouth and throat of the shark and help protect
it from sharp items in the shark's food.
RIGHT: The oral denticles are the largest of the ones that I have found so far, but not nearly as numerous as the dermal denticles.
|LEFT: There were only two vertebrae found in
the remains so far. The smaller one would have come from somewhere near
the tail. These vertebrae are very similar to those of Cretoxyrhina
and Squalicorax in appearance.
RIGHT: Two of the four large pieces of calcified cartilage that were recovered. These are probably parts of the upper jaw or palatoquadrate.
|LEFT: Another large piece of calcified
cartilage. This piece was colonized briefly by an oyster (Pseudoperna
congesta - circle). While it may have been living in a rich
environment for a while when the shark's carcass was decomposing, the
oyster was probably smothered when it was covered up with silt.
RIGHT: A close-up of the oyster spat, surrounded by denticles (black) and bits of cartilage (amber).
|LEFT: A group photo of most the teeth that I
collected. These teeth probably come from the upper jaw. As of the end of
the initial clean-up and preparation, we had collected an additional 200
RIGHT: These are replacement teeth that were in the process of being formed when the shark died. In sharks, the enameloid crown forms first and then the root is formed under it. There were about 50 replacement teeth recovered with the specimen
|LEFT: Once I started sorting the smaller
teeth, I discovered more than 30 of these mesial teeth (center row of the
upper jaw)... This made the identification complete... we were working
with a single upper jaw of the shark... with about 550 teeth in
total. (Note that my conclusion has been questioned by other more knowledgeable
RIGHT: A group of posterior lateral teeth that were preserved in articulation. The crowns of the teeth are interlocked and arranged like shingles on a roof... In this case, the teeth were at the back edge of the upper jaw.
|LEFT: My initial arrangement the teeth in the
upper jaw of this Ptychodus specimen. There are about 390 teeth in
the arranged portion with two groups of 50 posterior laterals on each
side. In life, there would be no spaces between the teeth in the jaw
plate... and the little mesial teeth in the center row would not be
visible (buried in gum tissue between the two rows of larger teeth.
RIGHT: My reconstruction of the upper jaw (palatoquadrate) with an
articulated jaw plate, in ventral view, and it's relationship to a
model of Ptychodus mortoni, based on: 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
The specimen has been donated to the Sternberg Museum of Natural History (FHSM VP-17606). Work on the site in June, 2011 did not recover any additional remains.
Suggested references on Ptychodus in Kansas and around the world:
More here on Ptychodus from the English Chalk
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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.
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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.
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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.
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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. 2013.The Palate Bones of a Fish?” – The First Specimen of Ptychodus mortoni (Chondrichthyes; Elasmobranchii) from Alabama. Bulletin of the Alabama Museum of Natural History 31(1):98-104.
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.
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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.
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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.
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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.
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LINKS: 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
Fort Hays Ptychodus mortoni - Earliest record of this species in Kansas - Early Coniacian
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