The genus Ptychodus is represented in the fossil records of Asia, Europe, Africa and the Americas. In North America, a dozen species are generally recognized from the Gulf, Texas and the Western Interior Seaway. Welton & Farish (1993) included ten tooth-designs from the Cretaceous of Texas, but some have subsequently been reassigned. Recent papers by Hamm (2010a,b) have resulted in the need to reassign some specimens.

Reported NA taxa include:

  • Ptychodus anonymus WILLISTON 1900 (M. Cenomanian-M. Turonian); Hamm 2010a reassigned younger reports of this taxon to P. rugosus.
  • P. atcoensis HAMM & CICIMURRI (2011) erected for Early Coniacian specimens from the Atco Formation of Texas.
  • P. connellyi MACLEOD & LAUGHTER 1980 (Campanian, TX): Hamm & Shimada (2004) synonymized the single specimen attributed to this species with P. martini and raised issues regarding the the specimen's actual age.
  • P. decurrens AGASSIZ 1843 (Albian-Cenomanian),
  • P. latissimus AGASSIZ 1843 (Coniacian-Campanian),
  • P. mammillaris AGASSIZ 1835 (Coniacian),
  • P. marginalis AGASSIZ 1839 (M. Cenomanian to M. Turonian); Hamm 2010b reassigned to this taxon some younger reports of P. polygyrus.
  • P. martini WILLISTON 1898 (Coniacian).
  • P. mortoni AGASSIZ 1839 ( Coniacian-Santonian),
  • P. occidentalis LEIDY 1868 (Cenomanian-Turonian),
  • P. polygyrus AGASSIZ 1839. (L. Santonian-E. Campanian; see Hamm 2010b),
  • P. rugosus DIXON 1850 (L. Coniacian - Santonian); Hamm 2010a reassigned to this taxon some younger reports of P. anonymus.
  • P. whipplei MARCOU 1858 (Turonian-Coniacian)

    Ptychodontid sharks have been a puzzle since they were first described in the mid-1880s and it is still uncertain whether they are more closely related to sharks or rays. Generally, they are known only from isolated teeth in late Cretaceous (Albian through Campanian) deposits. Several more or less complete jaw plates, consisting of a hundred or more teeth, have also been found. In a few cases, the teeth are associated with vertebrae and dermal scales that are very similar to those of Squalicorax. It was thought that the family Ptychodontidae was closely related to hybodontid sharks; however, Hamm (2008) argued they should be placed in a distinct order — Ptychodontiformes.

    The teeth of Ptychodus are arranged in parallel, interlocking rows which form a broad crushing surface on both the upper and lower jaws. The largest teeth are found in the upper medial tooth row. The crown of the tooth ranges from nearly flat in some species, to a strongly developed cusp in others. The crown is expanded to cover the weakly bilobate root on all faces and always bears a series of distinctively radiating or transverse enameloid ridges surrounded by a marginal area of varying width. Species of Ptychodus are defined on the basis of crown shape and cusp development. According to Cappetta (1987), the flatter teeth of Ptychodus latissimus and P. polygyrus formed grindstone-like plates that were ideal for crushing benthic mollusks with thick shells. By elevating the cusp above the basal surface of the tooth, Ptychodus rugosus and P. mortoni may have been better equipped to attack less well protected prey such as ammonites. Wear patterns on P. mortoni teeth show that they were used to crush hard-shelled prey. Coprolite-like structures composed of the finely crushed shells of immature inoceramids in the Smoky Hill Chalk suggest that ptychodids may have preferred these small mollusks to the thicker shelled adults.


     

     

    For additional Ptychodus species, see the Ptychodids of the Tropic Shale webpage.

    For more information on Kansas ptychodids, visit the webpage on ptychodid dentitions or Tom Caggiano's page on a Ptychodus anonymus dentition from the chalk.

    Selected References

    Agassiz, L., 1833-1843 [1835, 1839, 1843]. Recherches sur les poissons fossiles [5 volumes]. Imprimerie de Patitpierre, Neuch‚tel, 1420 pp.
    Cappetta, H., 1987a. Handbook of Paleoichthyology, Vol. 3B: Chondrichthyes 2 - Mesozoic and Cenozoic Elasmobranchii. - 193 S., 148 Fig.; Stuttgart (Gustav Fischer Verlag).
    Dixon, F., 1850. The Geology and Fossils of the Tertiary and Cretaceous Formations of Sussex. Longman, Brown, Green, & Longman, London, 408 pp.
    Hamm, S.A. 2008. Systematic, Stratigraphic, Geographic and Paleoecological Distribution of the Late Cretaceous shark Genus Ptychodus within the Western Interior Seaway. Unpublished Masterís thesis, the University of Texas at Dallas, 434 p. (PDF 10.8mb)
    Hamm, S.A. 2010a. The Late Cretaceous shark, Ptychodus rugosus, (Ptychodontidae) in the Western Interior Sea. Kansas Academy of Science Transactions 113(1-2):44-55.
    Hamm, S.A. 2010b. The Late Cretaceous shark Ptychodus marginalis in the Western Interior Seaway, USA. Journal of Paleontology 84(3):538-548.
    Hamm, S.A. and D.J. Cicimurri, 2011. Early Coniacian (Late Cretaceous) selachian fauna from the basal Atco Formation, Lower Austin Group, north central Texas; Paludicola [Rochester Institute of Vertebrate Paleontology] 8(3):107-127.
    Hamm, S.A. and K. Shimada 2004. A Late Cretaceous durophagus shark, Ptychodus martini WILLISTON, from Texas. Texas Journal of Science 56(3):215-222.
    Jaekel, O., 1898. Die Selachier aus dem oberen Muschel kalk Lothringens. Abhandlungen Geologische Spezialk. Elasass-Lothringen, Series 3 4:273-332.
    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. Rept., U.S. Geol. Surv. Terrs. (Hayden), 1:358 p., 37 pls.
    Lucas, S. G., 2006. Type locality of the Late Cretaceous shark Ptychodus whipplei MARCOU, northern New Mexico. In: Lucas, S. G. and Sullivan, R.M., (eds.), Late Cretaceous vertebrates from the Western Interior. New Mexico Museum of Natural History and Science Bulletin 35: 157- 59.
    MacLeod, N., and B. H. Slaughter, 1980. A new ptychodontid shark from the Upper Cretaceous of northeast Texas. Texas Journal of Science 32:333-335.
    Marcou, J., 1858. Geology of North America, with two reports on the prairies of Arkansas and Texas, the Rocky Mountains of New Mexico, and the Sierra Nevada of California, originally made for the United States government: Zurich, ZŁrcher and Furrer, 144 pp.
    Shimada, K., S. H. Kim, and C. K. Rigsby. 2007. Partial skull of Late Cretaceous durophagous shark, Ptychodus anonymus (Ptychodontidae), from Nebraska. Journal of Vertebrate Paleontology 27 (Supplement to Number 3):145A.
    Stewart, J. D. 1980. Reevaluation of the phylogenetic position of the Ptychodontidae. Transactions of the Kansas Academy of Science 83:154.
    Stewart, J. D. 1988. Paleoecology and the first West Coast record of the shark genus Ptychodus. Journal of Vertebrate Paleontology 8:27A.
    Welton, B. J., and R. F. Farish. 1993. The Collectorís Guide to Fossil Sharks and Rays from the Cretaceous of Texas. Before Time, Lewisville, Texas, 204 pp.
    Williamson T. E., J. I. Kirkland, and S. G. Lucas. 1991. The Cretaceous elasmobranch Ptychodus decurrens Agassiz from North America. Geobios 24:595-599.
    Williston, S.W. 1900a. Some fish teeth from the Kansas Cretaceous. Kansas University Quarterly 9(1):27-42, pl. VI-XIV.
    Williston, S. W. 1900b. Cretaceous fishes: selachians and pycnodonts. Kansas University Geological Survey 4:237-256.
    Woodward, A. S. 1887. On the dentition and affinities of the selachian genus Ptychodus Agassiz. Quarterly Journal of the Geological Society, London 43:121-131. Zangerl, R. 1981. Chondrichthyes I, Paleozoic Elasmobranchii; pp. 1-115 in H.-P. Schultze (ed.), Handbook of Paleoichthyology. Volume 3A. Gustav Fischer Verlag, Stuttgart.