Gonioceras
Encyclopedia
Gonioceras is an actinocerid
with a broad, low shell; flattened ventrally, convexly rounded dorsally; top and bottom meeting at an acute angle along the sides. In most the shell is rather thin, especially along the lateral portion. The aperture is contracted. Sutures from broad ventral and dorsal lobes, more narrowly rounded ventro-lateral and dorso-lateral saddles, and sharp pointed lateral lobes; more complex than in later Lambeoceras
. The siphuncle is typically subcentral but may be closer to the venter; armenocerid
in form with short segments and very short brims and containing a straight endosiphuncular canal system.
Gonioceras is derived from Armenoceras
and is the sole representative of the Gonioceratidae. It is found in the Chazy and Blackriveran of the Middle Ordovician
in the Champlain region of eastern North America and at the Paquette Rapids of the Ottawa River in Ontario. The genotype, Gonioceras anceps was named by Hall in 1847
Gonioceras was surely a bottom dweller that spent most of its time settled on the sea floor where it may have filled some of the niche filled by modern sting rays. However with its stiff outer shell, Gonioceras would not have been as mobile.
Actinocerida
The Actinocerida comprise an order of generally straight, medium to large cephalopods that lived during the early and middle Paleozoic, distinguished by a siphuncle composed of expanded segments that extend into the adjacent chambers, in which deposits formed within contain a system of radial...
with a broad, low shell; flattened ventrally, convexly rounded dorsally; top and bottom meeting at an acute angle along the sides. In most the shell is rather thin, especially along the lateral portion. The aperture is contracted. Sutures from broad ventral and dorsal lobes, more narrowly rounded ventro-lateral and dorso-lateral saddles, and sharp pointed lateral lobes; more complex than in later Lambeoceras
Lambeoceras
Lambeoceras is a rather large actinocerid with a convexly lenticular cross section from the Upper Ordovician of North America, and the sole representative of the family Lambeoceratidae.-Morphological Description:...
. The siphuncle is typically subcentral but may be closer to the venter; armenocerid
Armenoceratidae
Armenoceratidae is a family of early Paleozoic nautiloid cephalopods belonging to the Order Actinocerida.The Armenoceratidae, established by Troedsson is characterized by large, straight or slightly curved shells and large siphuncles with strongly expanded segments between the septa. Septal necks...
in form with short segments and very short brims and containing a straight endosiphuncular canal system.
Gonioceras is derived from Armenoceras
Armenoceras
Armenoceras is the principal genus of the Armenoceratidae, ranging from the late Whiterockian Stage in the early Middle Ordovician, through the remainder of the period and on into the Upper Silurian....
and is the sole representative of the Gonioceratidae. It is found in the Chazy and Blackriveran of the Middle Ordovician
Ordovician
The Ordovician is a geologic period and system, the second of six of the Paleozoic Era, and covers the time between 488.3±1.7 to 443.7±1.5 million years ago . It follows the Cambrian Period and is followed by the Silurian Period...
in the Champlain region of eastern North America and at the Paquette Rapids of the Ottawa River in Ontario. The genotype, Gonioceras anceps was named by Hall in 1847
Gonioceras was surely a bottom dweller that spent most of its time settled on the sea floor where it may have filled some of the niche filled by modern sting rays. However with its stiff outer shell, Gonioceras would not have been as mobile.
Refs
- Flower R.H. 1957. Studies of the Actinoceratida, New Mexico Bureau of Mines and Mineral Resources Memoir 2, Socorro NM .
- Teichert, C, 1964; Actinoceratoidea in the Treatise on Invertebrate Paleontology, Vol K; Teichert and Moore, eds; pub GSA & Univ Kansas