''Yinoceras'' is a genus of middle Permian goniatitid ammonite, the type genus for the subfamily

Yinoceratinae Yinoceratinae is one of three subfamilies of the goniatitid ammonoid family Pseudohaloritidae Pseudohaloritidae is the larger of two families that form the goniatitid superfamily Pseudohaloritoidea, the other being the monogenerc Maximitid ...

of the family

Pseudohaloritidae Pseudohaloritidae is the larger of two families that form the goniatitid superfamily Pseudohaloritoidea, the other being the monogenerc Maximitidae. They are part of the vast array of shelled cephalopods known as ammonoids that are more closel ...

. The shell of ''Yinoceras'' is involute, small to intermediate in size, subglobular or thickly discoidal with a very small umbilicus, convex flanks, and rounded venter. The surface is usually marked by weak constrictions and is characterized at maturity by coarse transverse ribs that bifurcate or sometimes trifurcate. The siphuncle is proportionally large and retrochoanitic (meaning the septal necks point toward the beginning of the shell); ventro-marginal in the first whorl but then migrates rapidly to become dorsal. The suture is goniatitic. The retrochoanitic siphuncle is more usual for earlier,

Devonian The Devonian ( ) is a geologic period and system of the Paleozoic era, spanning 60.3 million years from the end of the Silurian, million years ago (Mya), to the beginning of the Carboniferous, Mya. It is named after Devon, England, whe ...

, ammonoids and is a characteristic of the Nautiloidea. The dorsal siphuncle, characteristic of the Upper Devonian

Clymeniida Clymeniida is an order of ammonoid cephalopods from the Upper Devonian characterized by having an unusual dorsal siphuncle. They measured about in diameter and are restricted to Europe, North Africa, and possibly Australia. Morphologic charac ...

may say something about the orientation of ''Yinoceras'' during life.

References

* T.J. Frest, Brian F Glenister,& W.M. Furnish, 1981. Pennsylvanian-Permian Cheilceratacian Ammonoid Families Maximitidae and Pseudohaloritidae. Memoir 11. Journal of Paleontology V.55, Supplement to no.3, May 1981. * GONIAT Onlin

Pseudohaloritidae Goniatitida genera Permian ammonites {{Goniatitida-stub