''Domatoceras'' is a

nautiloid Nautiloids are a group of cephalopods (Mollusca) which originated in the Late Cambrian and are represented today by the living ''Nautilus'' and ''Allonautilus''. Fossil nautiloids are diverse and species rich, with over 2,500 recorded species. Th ...

genus and member of the

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 ...

from the

Pennsylvanian Pennsylvanian may refer to: * A person or thing from Pennsylvania * Pennsylvanian (geology) The Pennsylvanian ( , also known as Upper Carboniferous or Late Carboniferous) is, on the International Commission on Stratigraphy, ICS geologic timesc ...

and

Permian The Permian ( ) is a geologic period and System (stratigraphy), stratigraphic system which spans 47 million years, from the end of the Carboniferous Period million years ago (Mya), to the beginning of the Triassic Period 251.902 Mya. It is the s ...

with a wide spread distribution. The shell of ''Domatoceras'' is

evolute In the differential geometry of curves, the evolute of a curve is the locus (mathematics), locus of all its Center of curvature, centers of curvature. That is to say that when the center of curvature of each point on a curve is drawn, the result ...

, coiled with

whorls A whorl ( or ) is an individual circle, oval, volution or equivalent in a whorled pattern, which consists of a spiral or multiple concentric objects (including circles, ovals and arcs). In nature File:Photograph and axial plane floral diagram ...

touching but not overlapping, some growing to be moderately large. Whorl section subquadrate, higher than wide. Sides essentially straight to slightly bowed and slightly convergent on a broad slightly arched

venter Venter or Venters is an Afrikaans (and rarely, Jewish) surname, and may refer to: Venter * AJ Venter (b. 1973), South African rugby union footballer * Al J Venter (b. 1938), author * André Venter (b. 1970), South African rugby union footballer * ...

on the outer rim. Shoulder are narrow but rounded. Chambers are short but lengthen slightly before the mature living chamber,

septa SEPTA, the Southeastern Pennsylvania Transportation Authority, is a regional public transportation authority that operates bus, rapid transit, commuter rail, light rail, and electric trolleybus services for nearly four million people througho ...

close spaced, sutures form broad shallow

lateral Lateral is a geometric term of location which may also refer to: Biology and healthcare * Lateral (anatomy), a term of location meaning "towards the side" * Lateral cricoarytenoid muscle, an intrinsic muscle of the larynx * Lateral release ( ...

and

ventral Standard anatomical terms of location are used to describe unambiguously the anatomy of humans and other animals. The terms, typically derived from Latin or Greek roots, describe something in its standard anatomical position. This position prov ...

lobes and sharp ventro-lateral saddles. The dorsum in slightly impressed (indented) where it rides over the previous whorl. The

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

is subventral, located between the center and the ventral margin and, where known, slightly expanded so as to be longitudinally spindle shaped.

References

* Bernhard Kummel 1964. Nautiloidea-Nautilida

Treatise on Invertebrate Paleontology The ''Treatise on Invertebrate Paleontology,'' published from 1953–2007 by the Geological Society of America and the University of Kansas, then 2009–present by the University of Kansas Paleontological Institute, is a definitive multi-authore ...

. Geological Society of America and University of Kansas Press. {{Taxonbar, from=Q18352212 Nautiloids Pennsylvanian first appearances Permian genus extinctions