''Perimecoceras'' is a genus of
nothoceratids, nautilitoids in the order Oncocerida, with a slowly expanding, compressed, cyrtoconic shell, known from the Upper
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 central Europe.
''Perimecoceras'' is similar in general form to the
oncoceratid genus ''
Oonoceras'' from which it may have been derived, but differs in having a longer body chamber in proportion and in having concave segments to its
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 ...
. It as also the most likely ancestral nothoceratid, probably giving rise to ''
Blakeoceras'' and other Nothoceratidae.
''Perimecoceras'' probably lived on the sea floor, body chamber horizontal, phragmocone behind arched upward away from the bottom, using a combination of crawling and jet-swimming as it moved about.
References
* Sweet, W.C. 1964; Nautiloidea -Oncocerida;
Treatise on Invertebrate Paleontology
The ''Treatise on Invertebrate Paleontology'' (or ''TIP'') published by the Geological Society of America and the University of Kansas Press, is a definitive multi-authored work of some 50 volumes, written by more than 300 paleontologists, and co ...
, Part K; Geological Society of America and University of Kansas press; Teichert and Moore (eds)
''Perimecoceras''-Paleodb
Prehistoric nautiloid genera
Oncocerida
{{paleo-Nautiloidea-stub