Bassleroceras
Encyclopedia
Bassleroceras is an elongate upwardly curved, exogastric, genus with the venter on the under side more sharply rouned than the dorsum on the upper. The suphuncle is ventral, composed of thick-walled tubular segments in which connection rings thicken in towardly as in both the Ellesmerocerida
and primitive Tarphycerida
.
Bassleroceras is the type genus of the Bassleroceratidae
which Furnish and Glenister (1964) included in the Ellesmerocerida, but which Flower (1967) placed in the Tarphycerida. Bassleroceras gave rise to the Tarphycerida (sensu Furnish and Glenister, 1964) by evolving genera with tighter and tighter curvatures until becoming gyroconic, a character of the Estonioceratidae, a family of early tarphycerids.
Bassleroceras is found widespread in North America, e.g. New Mexico and New York, and in W. Australia.
Ellesmerocerida
The Ellesmerocerida is a order of primitive cephalopods belonging to the subclass Nautiloidea with a widespread distribution that lived during the Late Cambrian and Ordovician.-Morphology:...
and primitive Tarphycerida
Tarphycerida
The Tarphycerida were the first of the coiled cephalopods. They are found in marine sediments from the Lower Ordovician to the Middle Devonian. Some like Aphetoceras and Estonioceras are loosely coiled, gyroconic, others like Campbelloceras, Tarphyceras, and Trocholites are tightly coiled, but...
.
Bassleroceras is the type genus of the Bassleroceratidae
Bassleroceratidae
The Bassleroceratidae is a family of gradually expanding, smooth ellesmerocerids with a slight to moderate exogastric curvature, subcircular to strongly compressed cross section, and ventral orthochaonitc siphuncle. The ventral side is typically more sharply rounded than the dorsal side and septa...
which Furnish and Glenister (1964) included in the Ellesmerocerida, but which Flower (1967) placed in the Tarphycerida. Bassleroceras gave rise to the Tarphycerida (sensu Furnish and Glenister, 1964) by evolving genera with tighter and tighter curvatures until becoming gyroconic, a character of the Estonioceratidae, a family of early tarphycerids.
Bassleroceras is found widespread in North America, e.g. New Mexico and New York, and in W. Australia.
References
- Flower, Rousseau H. 1976. Ordovician Cephalopod Faunas and Their Role in Correlation, in Bassett, M.C. (Ed); The Ordovician System: Proceedings of a Paleontological Association Symposium; Birmingham, Eng. 1974; Univ of Wales and Welsh Nat’l Mus Press
- W. M. Furnish & Glenister, Brian F. 1964. Nautiloidea - Ellesmerocerida Treatise on invertebrate Paleontology, Part K. Teichert and Moore, eds.
- W. M. Furnish & Glenister, Brian F. 1964. Nautiloidea - Tarphycerida. ibid