Stratum.black
Ptychodus — Ptychodus decurrens infraphylum Gnathostomata Agassiz, 1839, Figured (NHMUK PV OR 32748)
Ptychodus decurrens infraphylum Gnathostomata Agassiz, 1839, Figured (NHMUK PV OR 32748) — © The Trustees of the Natural History Museum, London, Natural History Museum (London) Data Portal, CC BY 4.0

Shark / ray

Ptychodus

Shell-crushing shark

Ptychodus is the Cretaceous shark with pavement-like crushing teeth, each a rounded dome with transverse ridges, that fed on inoceramid clams in the Western Interior Seaway. Single teeth from the Niobrara Chalk, Greenhorn Limestone and Texas Eagle Ford are common and inexpensive; associated dentitions of hundreds of teeth are museum finds. Tooth size and ridge pattern separate the species (P. mortoni, P. whipplei, P. anonymus).

PhylumChordata
ClassChondrichthyes
FamilyPtychodontidae
GroupShark / ray
Rank (PBDB)genus· Paleobiology Database
AuthorAgassiz 1834· Paleobiology Database
Classification (PBDB)Chordata › Chondrichthyes › Lamniformes › Ptychodontidae· Paleobiology Database
Range (PBDB)165–66 Ma· Paleobiology Database
PBDB occurrences392· Paleobiology Database

Photographs

Ptychodus — Ptychodus decurrens infraphylum Gnathostomata Agassiz, 1839 (NHMUK PV P 61925)
Ptychodus decurrens infraphylum Gnathostomata Agassiz, 1839 (NHMUK PV P 61925) — © The Trustees of the Natural History Museum, London, Natural History Museum (London) Data Portal, CC BY 4.0
Ptychodus — Ptychodus latissimus infraphylum Gnathostomata Agassiz, 1843 (NHMUK PV P 11063 (1))
Ptychodus latissimus infraphylum Gnathostomata Agassiz, 1843 (NHMUK PV P 11063 (1)) — © The Trustees of the Natural History Museum, London, Natural History Museum (London) Data Portal, CC BY 4.0
Ptychodus — Ptychodus decurrens infraphylum Gnathostomata Agassiz, 1839 (NHMUK PV P 75509 (16))
Ptychodus decurrens infraphylum Gnathostomata Agassiz, 1839 (NHMUK PV P 75509 (16)) — © The Trustees of the Natural History Museum, London, Natural History Museum (London) Data Portal, CC BY 4.0

Age

Formations

Elsewhere

Cite this article

Stratum Study. "Ptychodus" (Taxon). Stratum Study pack 2026.09, as of 2026-09-19. https://stratum.black/study/taxa/ptychodus. Accessed 2026-09-20.

BibTeX · CSL-JSON

@misc{stratum-ptychodus,
  title        = {Ptychodus},
  author       = {{Stratum Study}},
  howpublished = {\url{https://stratum.black/study/taxa/ptychodus}},
  year         = {2026},
  note         = {Taxon article, Stratum Study pack 2026.09, as of 2026-09-19; sources: stratum, pbdb, wikidata, nhm. Accessed 2026-09-20.}
}

Citations carry the pack version and the article's as-of date so they resolve to the same text later. The facts themselves belong to the sources listed below; cite those for the science.