Dimeroceratidae
Encyclopedia
Dimeroceratidae is one of three families in the Dimeroceratoidea , a goniatid superfamily included in the Ammonoidea, which are extinct shelled cephalopods with a greater affinity to modern coleods
than to shelled nautiliods.
The family Dimeroceratidae is based in the genus Dimeroceras which was previously included in the Cheiloceratidae
in the Treatise on Invertebrate Paleontology
, a family of gonitites in which sutures form 4 to 12 lobes and the ventral one is undivided. The Cheliceratidae, now redefined, is based on Cheiloceras
, a subglublar to thickly lentiuclar form with a closed umbilicus to which Dimeroceras is similar, except in Dimeroceras the umbilical lobe is outside the umbilucus and the lateral lobe is large.
The Dimeroceratidae are derived from the Cheiloceratid genus Torleyoceras through the ancestral Paradimeroceras which gave rise to Dimeroceras, according to Saunders et al 1999. Paratornoceras and Acrimeroceras
are included.
Dimeroceratids have been found in the Devonian of China and Australia.
Coleoidea
Subclass Coleoidea, or Dibranchiata, is the grouping of cephalopods containing all the primarily soft-bodied creatures. Unlike its sister group Nautiloidea, whose members have a rigid outer shell for protection, the coleoids have at most an internal bone or shell that is used for buoyancy or support...
than to shelled nautiliods.
The family Dimeroceratidae is based in the genus Dimeroceras which was previously included in the Cheiloceratidae
Cheiloceratidae
Cheiloceratidae is a family of ammonoid cephalopods included in the goniatitid suborder Tornoceratina in which the suture has 4 to 12 lobes, the ventral one undivided and those in the lateral areas originating as subdivisions of internal and external lateral saddles.-Taxonomy:The taxonomy of the...
in the Treatise on Invertebrate Paleontology
Treatise on Invertebrate Paleontology
The Treatise on Invertebrate Paleontology published by the Geological Society of America and the University of Kansas Press, is a definitive multi-authored work of some 50 volumes, written by more than 300 paleontologists, and covering every phylum, class, order, family, and genus of fossil and...
, a family of gonitites in which sutures form 4 to 12 lobes and the ventral one is undivided. The Cheliceratidae, now redefined, is based on Cheiloceras
Cheiloceras
Cheiloceras is a subglobular to thickly lenticular goniatite with a closed umbilicus from the Upper Devonian and type genus for the Cheiloceratidae....
, a subglublar to thickly lentiuclar form with a closed umbilicus to which Dimeroceras is similar, except in Dimeroceras the umbilical lobe is outside the umbilucus and the lateral lobe is large.
The Dimeroceratidae are derived from the Cheiloceratid genus Torleyoceras through the ancestral Paradimeroceras which gave rise to Dimeroceras, according to Saunders et al 1999. Paratornoceras and Acrimeroceras
Acrimeroceras
Acrimeroceras is an oxyconic Devonian gonitite and one of three genera included in the subfamily Paratornoceratinae. The others being Paratornoceras and Paratoceras or ex Polonites....
are included.
Dimeroceratids have been found in the Devonian of China and Australia.