Allotrioceras
Encyclopedia
Allotrioceras is a tubular fossil from the middle Chazyan
(Middle Ordovician) of New York state
, collected by Rousseau H. Flower
and included by him in the Endocerida and placed in a new family, the Allotrioceratidae. Allotrioceras is characterized by a lateral pair of subequal endocones separated by a straight partition that extends more than half way across from either the dorsal or vental side, as perceived, and runs along the length. What remains is thought to represent the siphuncle
which ranges from about 8 millimetre (0.31496062992126 in) to about 15 millimetre (0.590551181102362 in) in diameter.
Some endocerids, derived from the Proterocameroceratidae
, Najaceras
, Cacheoceras, and Williamsoceras
, have a longitudinal dorsal or ventral process, or both about which the endocones are formed, which the partitian of Allotrioceras has somewhat of a resemblance. In the Chihliocreratidae, also derived from the Proterocameroceratidae, the main endocones are flanked by two smaller endocones, one on each side. Longitudinal partitions and multiple endocones are not unknown in the order. Simply on the basis of either, Allotrioceras can not be excluded.
The holotype
of Allotrioceras, Allotrioceras bifercatum Flower 1955, rests in the collection of the New Mexico Museum of Natural History and Science
in Albuquerque, New Mexico
.
Chazy Formation
The Chazy Reef Formation is a mid-Ordovician limestone deposit that consists of some of the oldest reef systems built by a community of organisms rather than the deposit of a limited range of similar organisms, such as Stromatolite mounds deposited by ancient cyanobacteria...
(Middle Ordovician) of New York state
New York
New York is a state in the Northeastern region of the United States. It is the nation's third most populous state. New York is bordered by New Jersey and Pennsylvania to the south, and by Connecticut, Massachusetts and Vermont to the east...
, collected by Rousseau H. Flower
Rousseau H. Flower
Rousseau Hayner Flower was an extremely prolific 20th century paleontologist, known for his eccentric personality.- Career :Although trained as an entomologist, and a specialist in dragonflies and orthopterans, Flower began studying paleontology in the middle of the 1930s...
and included by him in the Endocerida and placed in a new family, the Allotrioceratidae. Allotrioceras is characterized by a lateral pair of subequal endocones separated by a straight partition that extends more than half way across from either the dorsal or vental side, as perceived, and runs along the length. What remains is thought to represent 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 ranges from about 8 millimetre (0.31496062992126 in) to about 15 millimetre (0.590551181102362 in) in diameter.
Some endocerids, derived from the Proterocameroceratidae
Proterocameroceratidae
The Proterocameroceratidae were the first of the Endocerida. They began early in the Ordovician with Proendoceras or similar genus which had developed endocones, replacing the diaphragms of the ellesmerocerid ancestor....
, Najaceras
Najaceras
Najaceras is a genus of straight, slender endocerid known only from the Whiterockian age Oil Creek Limestone of Oklahoma, introduced and named by Rousseau Flower in 1971 and further described by him in 1976....
, Cacheoceras, and Williamsoceras
Williamsoceras
Williamsoceras is an endocerid that Rousseau Flower added to his Allotrioceratidae on the basis of having a vertical partition within the siphuncle, known as a ventral process, with inter-connecting tubule-like structures along its margin where intercepted by endocones...
, have a longitudinal dorsal or ventral process, or both about which the endocones are formed, which the partitian of Allotrioceras has somewhat of a resemblance. In the Chihliocreratidae, also derived from the Proterocameroceratidae, the main endocones are flanked by two smaller endocones, one on each side. Longitudinal partitions and multiple endocones are not unknown in the order. Simply on the basis of either, Allotrioceras can not be excluded.
The holotype
Holotype
A holotype is a single physical example of an organism, known to have been used when the species was formally described. It is either the single such physical example or one of several such, but explicitly designated as the holotype...
of Allotrioceras, Allotrioceras bifercatum Flower 1955, rests in the collection of the New Mexico Museum of Natural History and Science
New Mexico Museum of Natural History and Science
The New Mexico Museum of Natural History and Science is a natural history and science museum in Albuquerque, New Mexico near Old Town Albuquerque. The Museum was founded in 1986....
in Albuquerque, New Mexico
Albuquerque, New Mexico
Albuquerque is the largest city in the state of New Mexico, United States. It is the county seat of Bernalillo County and is situated in the central part of the state, straddling the Rio Grande. The city population was 545,852 as of the 2010 Census and ranks as the 32nd-largest city in the U.S. As...
.
Other sources
- Curt Teichert 1964, Encoceratoidea, K160—__ in Vol K Treatise on Invertebrate PaleontologyTreatise on Invertebrate PaleontologyThe 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...
, Teichert C and Moore, R, C, eds, GSA and Univ Kansas Press. - Collections of the New Mexico Museum of Natural History and Science,Albuquerque, NM.