''Grypoceras'' is a coiled nautiloid cephalopod from the

Triassic The Triassic ( ) is a geologic period and system (stratigraphy), system which spans 50.6 million years from the end of the Permian Period 251.902 million years ago (Year#Abbreviations yr and ya, Mya), to the beginning of the Jurassic Period 201.36 ...

of western North America, southern Asia, and Europe that belongs to the nautilid family Grypoceratidae. Named by

Alpheus Hyatt Alpheus Hyatt (April 5, 1838 – January 15, 1902) was an American zoologist and palaeontologist. Biography Alpheus Hyatt II was born in Washington, D.C. to Alpheus Hyatt and Harriet Randolph (King) Hyatt. He briefly attended the Maryla ...

in 1883, the shell of ''Grypoceras'' is essentially involute with a subtriangular cross section, widest across the umbilical shoulders, with flanks fairing toward a narrow flattened venter. Sutures on flanks are with smooth, deep lobes and with shallow ventral lobes. The earlier, related '' Domatoceras'' is evolute, with a more quadrate whorl section. '' Gryponautilus'', from the Upper Triassic, is more strongly involute and has a sharply keeled venter.

References

* Bernhard Kummel, 1964, Nautiloidea-Nautilida. Treatise on Invertebrate Paleontology, Part K. Geological Society of America and University of Kansas Press.
Paleobiology Database ''Grypoceras'' entry
accessed 7 July 2012 Nautiloids {{paleo-cephalopod-stub