The Plectoceratidae is a family of
tarphycerids in the suborder
Barrandeocerina established as a place for the genus ''
Plectoceras''; defined (Sweet 1964) simply as coiled, costate barrandeocerids with subcentral adult
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 ...
.
According to Sweet, in the original ''
Treatise
A treatise is a formal and systematic written discourse on some subject, generally longer and treating it in greater depth than an essay, and more concerned with investigating or exposing the principles of the subject and its conclusions."Treat ...
'' Part K, the Plectoceratidae included only ''Plectoceras''. Flower, 1984, however added six other genera, two new and four removed from both the
Barrandeoceratidae and
Apsidoceratidae
The Apsidoceratidae is a family of Middle and Upper Ordovician Barrandeocerina, (a suborder of tarphycerids), characterized by curved or coiled, smooth, transversely marked, or laterally costate shells, with a conspicuous hyponomic sinus. Early wh ...
. Genera according to Flower, 1984 are:
''
Plectoceras'' Hyatt -type genus
''
Avilionella'' -removed from Barradeoceratidae
''
Bodeiceras'', Flower 1984. added
''
Chidleyenoceras'' - removed from the Apsidoceratidae
''
Metaplectoceras'', Flower (?synonym for Plectoceras)
''
Laureloceras'' Flower 1957, removed from Barrandeoceratidae
''
Laurelplecoceras'' Flower 1984 -added
According to Flower, 1984, ''Plectoceras'', and therefore the Plectoceratidae, is derived from the Tarphyceratid genus ''
Campbelloceras'' while ''
Barrandeoceras'', and therefore the Barrandeoceratidae, is derived from ''
Centrotarphyceras''. The inclusion of ''Laureloceras'' expands the range of the Plectoceratidae into the Middle
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 the Upper Ordovician when it had been with only ''Plectoceras''
References
*Walter C Sweet, 1964. Nautiloidea-Barrandeocerida; Treatise on Invertebrate Paleontology Part K Mollusca 3. Geological Society of America and University of Kansas Press
*Rousseau H. Flower, 1984. ''Bodeiceras''; a New Mohawkian Oxycone, with Revision of the Older Barrandeocerida and Discussion of the Status of the Order. Journal of Paleontology v. 58, no.6, pp 1372–1379, Nov. 1984.
{{Taxonbar, from=Q7204384
Tarphycerida
Ordovician cephalopods
Cephalopod families