Sphaeorthoceratidae is an extinct family of

orthocone An orthocone is an unusually long straight shell of a nautiloid cephalopod.; During the 18th and 19th centuries, all shells of this type were named ''Orthoceras'', creating a wastebasket taxon, but it is now known that many groups of nautiloids d ...

cephalopods that lived in the Paleozoic Era. They were similar to the nautiloid ''

Michelinoceras ''Michelinoceras'' is the oldest known genus of the Michelinocerida, more commonly known as the Orthocerida, characterized by long, slender, nearly cylindrical orthocones with a circular cross section, long camerae, very long body chambers, and a ...

'' in the apex, but had shorter necks to their septa that were orthochoanitic or suborthochoanitic. The sphaerorthoceratids were significant in cephalopod evolution because they may have given rise to the

bactritid The Bactritida are a small order of more or less straight-shelled (orthoconic) cephalopods that first appeared during the Emsian stage of the Devonian period (407 million years ago) with questionable origins in Pragian stage before 409 million ye ...

s, which in turn were the ancestors of

ammonoid Ammonoids are a group of extinct marine mollusc animals in the subclass Ammonoidea of the class Cephalopoda. These molluscs, commonly referred to as ammonites, are more closely related to living coleoids (i.e., octopuses, squid and cuttlefish) ...

s and coleoids. The family lived in the middle Paleozoic, ranging from the Sheinwoodian age of 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 ...

Period to the Famennian age of the

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 ...

Period, or about 428 to 361 Ma.

References

{{Taxonbar, from=Q7576563 Orthocerida Cephalopod families