''Parasphaerorthoceras'' is an extinct

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 ...

genus, a nautiloid cephalopod, that lived in what would be Europe and north Africa during the

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 ...

from 422.9—418.1

mya Mya may refer to: Brands and product names * Mya (program), an intelligent personal assistant created by Motorola * Mya (TV channel), an Italian Television channel * Midwest Young Artists, a comprehensive youth music program Codes * Burmese ...

, having existed for approximately .

Taxonomy

''Parasphaerorthoceras'' was named by Ristedt in 1968, who placed it in the

Sphaerorthoceratidae Sphaeorthoceratidae is an extinct family of orthocone cephalopods that lived in the Paleozoic Era. They were similar to the nautiloid ''Michelinoceras'' in the apex, but had shorter necks to their septa that were orthochoanitic or suborthochoa ...

, which he also named. ''Parasphaerorthoceras'' is listed in Jack Sepkoski's (2002) list of Cephalopod genera under

Orthocerida 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 ...

J. J. Sepkoski. 2002. A compendium of fossil marine animal genera. Bulletins of American Paleontology 363:1-560 It is also classified and described in some detail in Björn Kröger's 2008 paper on Silurian and Devonian nautiloids from MoroccoBjörn Kröger, 2008. Nautiloids Before and During the Origin of Ammmonoids in a Siluro-Devonian Section of the Tafilalt, Anti-atlas, Morocco. Special Papers in Palaeontology; the Palaentology Association, London.

Morphology

The shell of ''Parasphaerorthoceras'' is generally straight, (" orthoconic") with a circular cross section. The initial chamber is spheroidal, followed by a distinct constriction. The apical part of the shell is wavy but becomes striated, then smooth in later growth stages. The siphuncle is central or subcentral. Septal necks suborthochoanitic. Sutures are straight. In life, these animals may have been similar to the modern

squid True squid are molluscs with an elongated soft body, large eyes, eight arms, and two tentacles in the superorder Decapodiformes, though many other molluscs within the broader Neocoleoidea are also called squid despite not strictly fitting t ...

, except for the long shell.

Fossil distribution

''Parasphaerothoceras'' species have been found in Austria, Italy, Sardinia, and Morocco.

References

{{Taxonbar, from=Q7135990 Prehistoric nautiloid genera Silurian animals Prehistoric animals of Europe