''Grypoceras'' is a coiled nautiloid

cephalopod A cephalopod is any member of the molluscan Taxonomic rank, class Cephalopoda (Greek language, Greek plural , ; "head-feet") such as a squid, octopus, cuttlefish, or nautilus. These exclusively marine animals are characterized by bilateral symm ...

from the

Triassic The Triassic ( ; sometimes symbolized 🝈) is a geologic period and system which spans 50.5 million years from the end of the Permian Period 251.902 million years ago ( Mya), to the beginning of the Jurassic Period 201.4 Mya. The Triassic is t ...

of western North America, southern Asia, and Europe that belongs to the nautilid family

Grypoceratidae Grypoceratidae is the longest-lived family of the Trigonoceratoidea, or of the near equivalent Centroceratina; members of the Nautilida from the Upper Paleozoic and Triassic.Kummel,B. 1964. Nautiloidea-Nautilida, Treatise on Invertebrate Paleont ...

. Named by

Alpheus Hyatt Alpheus Hyatt (April 5, 1838 – January 15, 1902) was an American zoologist and palaeontologist. Hyatt served as the founding president of the American Society of Naturalists from 1883 to 1884 and was the founding editor of the journal '' T ...

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