''Triendoceras'' is a genus of fairly large

endocerid Endocerida, from Ancient Greek ἔνδον (''éndon''), meaning "inside", and κέρας (''kéras''), meaning "horn", is an extinct nautiloid order, a group of cephalopods from the Lower Paleozoic with cone-like deposits in their siphuncle. End ...

named by Flower (1958), included in the

Endoceratidae Endoceratidae, from Ancient Greek ἔνδον (''éndon''), meaning "inside", and κέρας (''kéras''), meaning "horn", is a family of large to very large straight-shelled Nautiloidea, nautiloid cephalopods belonging to the order Endocerida th ...

by Teichert (1964), characterized by a holochoanitic ventral siphuncle in which the cross section through the endocones has an opening in the shape of an isosceles triangle with a sharp apex (corner) pointing down. ''Triendoceras'' is found in the upper Lower Ordovician of Quebec and New York in North America and possibly in Ohio, and in eastern Europe. The

type species In International_Code_of_Zoological_Nomenclature, zoological nomenclature, a type species (''species typica'') is the species name with which the name of a genus or subgenus is considered to be permanently taxonomically associated, i.e., the spe ...

is ''T. montrealense''.

References

*Flower, R. H 1958, Some Chazyan and Mohawkian Endoceratida, Jour Paleon V 32, No 2, pp 433–458, May 1858 *Teichert, Curt 1964. Endoceratoidea;

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 ...

, Part K Mollusca 3; Geol Soc of America and University of Kansas Press {{Taxonbar, from=Q7841436 Endoceratidae Prehistoric nautiloid genera Paleozoic life of Quebec Fossil taxa described in 1958