Pseudactinoceraidae is a family in the cephalopod order

Pseudorthocerida Pseudorthocerida is an order of generally straight longiconic orthoceratoids with a subcentral to marginal cyrtochoanitic siphuncle composed of variably expanded segments which may contain internal deposits that may develop into a continuous p ...

, known from the

Upper 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, wher ...

and Lower

Carboniferous The Carboniferous ( ) is a geologic period and system of the Paleozoic that spans 60 million years from the end of the Devonian Period million years ago ( Mya), to the beginning of the Permian Period, million years ago. The name ''Carbonifero ...

( Mississippian).Nautiloidea-Orthocerida by Walter C Sweet, Treatise on Invertebrate Paleontology Part K Mollusca 3, R.C Moore (ed) 1964 Pseuactinocerids are characterized by elongated, straight and gently curved shells with a subcentral

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 ...

composed of broadly expanded segments in the adult in which there are internal deposits pieced by two series of radial canals. Deposits form initially at the septal openings and grow mostly forward to connect with the next deposit in the anterior part of the next segment. The radial canals connect the interior of the segments with the ends of the connecting rings as they approach adjacent septa. Camerae, which are generally short, are commonly filled with organic deposits. Macroloxoceras, a Devonian Homeomorph of the Actinoceratida, part 2 Menoir 2, Studies of the Actinoceatidae by Roussaur H Flower. New Mexico Bureau of Mines and Mineral Resources, Socorro NM 1957 Flower preferred the term Macroloxoceratidae, (ex Macrolooxcerainae, a subfamily in the Pseuorthoceratidae) which he proposed; reasoning that since '' Macroloxoceras'' is based on an adult specimen and is better defined than '' Pseudactinoceras'' which is based on a juvenile portion of a phagmocone, it is a better choice by which the (sub)family should be named.

References

{{Taxonbar, from=Q7254144 Orthoceratoidea Late Devonian first appearances Late Devonian animals Mississippian extinctions