Tornoceratina is one of two

suborder Order ( la, ordo) is one of the eight major hierarchical taxonomic ranks in Linnaean taxonomy. It is classified between family and class. In biological classification, the order is a taxonomic rank used in the classification of organisms and ...

s included in the

Goniatitida Goniatids, informally goniatites, are Ammonoidea, ammonoid cephalopods that form the order Goniatitida, derived from the more primitive Agoniatitida during the Middle Devonian some 390 million years ago (around Eifelian stage). Goniatites (goniat ...

, characterized by generally involute, subdiscoidal shells and by sutures in which the ventral ones are undivided. Sutural lobes increase in number during the course of life of the individual, typically developed from the internal and external saddles. The

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 ...

is prochoanitic, with septal necks projecting forward. Derivation is from the

Anarcestida Agoniatitida, also known as the Anarcestida, is the ancestral order within the cephalopod subclass Ammonoidea originating from bactritoid nautiloids, that lived in what would become Africa, Asia, Australia, Europe, and North America during t ...

in the middle Devonian.

References

* Miller, Furnish, and Schindewolf, 1957. Paleozoic Ammonoidea. Treastise on Invertebrate Paleontology, Part L. Geological Society of America. * Tornoceratina i
Goniat
on line, Mar. 5, 2015
The Paleobiology Database
Oct.1, 2007 Goniatitida Middle Devonian first appearances Guadalupian extinctions {{Goniatitida-stub