''Lyecoceras'' is a gender of slender endogastrically curved

orthocerid Orthocerida is an order of extinct Orthoceratoid cephalopods also known as the Michelinocerida that lived from the Early Ordovician () possibly to the Late Triassic (). A fossil found in the Caucasus suggests they may even have survived until ...

s, so determined by identification of the hyponomic sinus on the concave side. The

siphuncle The siphuncle is a strand of tissue passing longitudinally through the shell of a cephalopod mollusk. Only cephalopods with chambered shells have siphuncles, such as the extinct ammonites and belemnites, and the living nautiluses, cuttlefish, and ...

is dorsal of the center, toward the convex side of the shell. The surface has faint longitudinal striae and is encircled by weak annulations. ''Lyecoceras'' was first found in the Middle

Silurian The Silurian ( ) is a geologic period and system spanning 24.6 million years from the end of the Ordovician Period, at million years ago ( Mya), to the beginning of the Devonian Period, Mya. The Silurian is the shortest period of the Paleozo ...

of Sweden, and since in the Silurian of Sochuan Provence, China.

References

* Walter C. Sweet, 1964. Nautiloidea - Orthocerida; Treatise on Invertebrate Paleontology, Part K. Geological Society of America Prehistoric nautiloid genera {{paleo-nautiloidea-stub