''Allotrioceras'' is a tubular fossil from the
Middle Ordovician
The Ordovician ( ) is a geologic period and system, the second of six periods of the Paleozoic Era, and the second of twelve periods of the Phanerozoic Eon. The Ordovician spans 41.6 million years from the end of the Cambrian Period Ma (milli ...
of the state of
New York
New York most commonly refers to:
* New York (state), a state in the northeastern United States
* New York City, the most populous city in the United States, located in the state of New York
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* ...
, collected by
Rousseau H. Flower
Rousseau Hayner Flower (1913–1988) 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 study ...
; included by him in the
Endocerida
Endocerida, from Ancient Greek ἔνδον (''éndon''), meaning "inside", and κέρας (''kéras''), meaning "horn", is an extinct nautiloid order, a group of cephalopods from the Lower Paleozoic with cone-like deposits in their siphuncle. End ...
and placed in a new family, the Allotrioceratidae. ''Allotrioceras'' is characterized by a lateral pair of subequal conical structures, resembling the endocones of endocerids, separated by a straight partition that extends more than half way across from either the dorsal or ventral side, as perceived, and runs along the length. What remains is thought to represent a
siphuncle
The siphuncle is a strand of biological tissue, tissue passing longitudinally through the mollusc shell, shell of a cephalopod mollusc. Only cephalopods with chambered shells have siphuncles, such as the extinct ammonites and belemnites, and the li ...
, which ranges from about 8 millimeters (0.3 in) to about 15 millimeters (0.6 in) in diameter. On the basis of diagnosis, inclusion of ''Allotrioceras'' and the Allotrioceratidae, for which it is the type, in the endocerida seems at best tentative.
Some endocerids, derived from the
Proterocameroceratidae, ''
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.
''Najaceras'' is characterized by ...
'', ''
Cacheoceras'', and ''
Williamsoceras'', have a longitudinal dorsal or ventral process, or both about which the endocones are formed, which the partitian of Allotrioceras somewhat resembles. In the Chihliocreratidae, also derived from the Proterocameroceratidae,
[{Rousseau H. Flower 1958. Some Chazyan and Mohawkian Endoceratida, Journal of Paleontology Vol32, no3 pp 433-458] the main endocones are flanked by two smaller endocones, one on each side, superficially resembling ''Allotrioceras''.
The
holotype
A holotype (Latin: ''holotypus'') is a single physical example (or illustration) of an organism used when the species (or lower-ranked taxon) was formally described. It is either the single such physical example (or illustration) or one of s ...
of ''Allotrioceras'', ''Allotrioceras bifercatum'' Flower 1955, rests in the collection of the
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. It operates as a public revenue facility of the New Mexico Departme ...
in
Albuquerque, New Mexico
Albuquerque ( ; ), also known as ABQ, Burque, the Duke City, and in the past 'the Q', is the List of municipalities in New Mexico, most populous city in the U.S. state of New Mexico, and the county seat of Bernalillo County, New Mexico, Bernal ...
.
References
* Curt Teichert 1964, Encoceratoidea, K160—__ in Vol K
Treatise on Invertebrate Paleontology
The ''Treatise on Invertebrate Paleontology,'' published from 1953–2007 by the Geological Society of America and the University of Kansas, then 2009–present by the University of Kansas Paleontological Institute, is a definitive multi-authore ...
, 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.
{{Taxonbar, from=Q4733224
Prehistoric nautiloid genera
Ordovician molluscs
Fossils of the United States
Taxa named by Rousseau H. Flower