Tajaroceras
Encyclopedia
Tejaroceras is an extinct slender cephalopod from the uppermost Lower Ordovician of western North America, belonging to the Orthocerid
family Troedssonellidae
.
The shell of Tajaroceras is smooth and straight. The siphuncle
which is at least 0.35 the shell diameter is subcentral. Septal necks are short and the connecting rings are thin and homogenous. The distinguishing feature of Tajaroceras lies within its siphuncle. Along the ventral side, within the siphuncle, is a continuous rod, much like that found in a group known as rod-bearing Baltoceratidae
. On the dorsal sde, overlying within, are annular deposits that grow forward to form a continuous lining that ultimately rests against the ventral rod, leaving a small opening slightly above the center. The camerae contain deposits of organic calcite.
Tajaroceras, first described by Hook and Flower (1976), has been found in the Upper Cassinian Wahwah Limestone in Western Utah and in the equivalent Florida Mountains Formation in Southern New Mexico and is the probable ancestor of the Troedssonellidae, being followed in overlapping sequence by Buttsoceras. The type, Tajaroceras wardae, was found 55–65 ft above the base of the Wahwah Ls in the Ibex area of western Utah.
Tejaroceras is named for Jane Shaw Ward's character, the Tejar.
Orthocerida
Orthocerida is an order of extinct nautiloid cephalopods also known as the Michelinocerda that lived from the Early Ordovician possibly to the Late Triassic . A fossil found in the Caucasus suggests they may even have survived until the Early Cretaceous...
family Troedssonellidae
Troedssonellidae
Troedssonellidae is a family of orthoceroid cephalopods from the Ordovician, derived from rod-bearing Baltoceratidae, that have a continuous lining within the siphuncle that resembles very thin and slender endocones. Shells are generally slender and orthoconic. The siphuncle is central or...
.
The shell of Tajaroceras is smooth and straight. The siphuncle
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 Spirula...
which is at least 0.35 the shell diameter is subcentral. Septal necks are short and the connecting rings are thin and homogenous. The distinguishing feature of Tajaroceras lies within its siphuncle. Along the ventral side, within the siphuncle, is a continuous rod, much like that found in a group known as rod-bearing Baltoceratidae
Baltoceratidae
Baltoceratidae is an extinct family of orthoconic cephalopods belonging to the subclass Nautiloidea endemic to what would be Asia, Australia, Europe, North America, and South America during the Ordovician living from about 480–460 mya, existing for approximately .-Taxonomy:Baltoceratidae was...
. On the dorsal sde, overlying within, are annular deposits that grow forward to form a continuous lining that ultimately rests against the ventral rod, leaving a small opening slightly above the center. The camerae contain deposits of organic calcite.
Tajaroceras, first described by Hook and Flower (1976), has been found in the Upper Cassinian Wahwah Limestone in Western Utah and in the equivalent Florida Mountains Formation in Southern New Mexico and is the probable ancestor of the Troedssonellidae, being followed in overlapping sequence by Buttsoceras. The type, Tajaroceras wardae, was found 55–65 ft above the base of the Wahwah Ls in the Ibex area of western Utah.
Tejaroceras is named for Jane Shaw Ward's character, the Tejar.
References
- Hook,S.C.and Flower,R.H. 1976. Tajaroceras and the origin of the Troedssonellidae: Jour Paleotology v.50, p. 293-300
- Hook,S.C.and Flower,R.H. 1977. Late Canadian (Zones J,K) Cephalopod Faunas from Southwestern United States: Memoir 32, New Mexico Bureau of Mines and Mineral Resources.