Polyptychoceras
Encyclopedia
Polyptychoceras is an extinct genus
of ammonite
from the Late Cretaceous
of Asia
, Europe
, and North
and South America
. It was first named by Hisakatsu Yabe in 1927, and contains eight species and a subgenus, Subtychoceras, which contains one species.
It also contains one subgenus
, Subptychoceras, which contains one subspecies
, S. yubarense. P. pseudogaultinum could reach a length of 100 - 120 mm, while S. yubarense could reach a maximum length of 200 mm.
Polyptychoceras shells have an abrupt weight increase after formation of the initial shaft, which represents the shell's automatic balance condition. This would have caused the shell to topple over if on land. The soft body of the animal would have to have been large, in order to keep the falling shaft off of the ground. The body would not have been resistant to the pressing shell.
Although the shafts in the fossils of the shells are usually parallel to each other, small aberrations during each growth stage often caused abrupt constrictions in the shape of the shell.
and Upper Coniacian
faunal stage
s of the Late Cretaceous
Epoch
. Polyptychoceras was probably buoyant, and swam in a slow, somewhat up-and-down locomotion. It also likely preferred living in sheltered parts of deep sea levels, although how deep is uncertain. Subptychoceras yubarense was likely very long like an eel, and preferred a benthic mode of life.
Genus
In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...
of ammonite
Ammonite
Ammonite, as a zoological or paleontological term, refers to any member of the Ammonoidea an extinct subclass within the Molluscan class Cephalopoda which are more closely related to living coleoids Ammonite, as a zoological or paleontological term, refers to any member of the Ammonoidea an extinct...
from the Late Cretaceous
Late Cretaceous
The Late Cretaceous is the younger of two epochs into which the Cretaceous period is divided in the geologic timescale. Rock strata from this epoch form the Upper Cretaceous series...
of Asia
Asia
Asia is the world's largest and most populous continent, located primarily in the eastern and northern hemispheres. It covers 8.7% of the Earth's total surface area and with approximately 3.879 billion people, it hosts 60% of the world's current human population...
, Europe
Europe
Europe is, by convention, one of the world's seven continents. Comprising the westernmost peninsula of Eurasia, Europe is generally 'divided' from Asia to its east by the watershed divides of the Ural and Caucasus Mountains, the Ural River, the Caspian and Black Seas, and the waterways connecting...
, and North
North America
North America is a continent wholly within the Northern Hemisphere and almost wholly within the Western Hemisphere. It is also considered a northern subcontinent of the Americas...
and South America
South America
South America is a continent situated in the Western Hemisphere, mostly in the Southern Hemisphere, with a relatively small portion in the Northern Hemisphere. The continent is also considered a subcontinent of the Americas. It is bordered on the west by the Pacific Ocean and on the north and east...
. It was first named by Hisakatsu Yabe in 1927, and contains eight species and a subgenus, Subtychoceras, which contains one species.
Specimens
- P. mihoense
- P. haradanuin (Yokoyama)
- P. obatai
- P. obliquecostatum
- P. subunduratum
- P. obstrictum (Jimbo)
- P. vancouverensis located around the Trent River and Puntledge River. Due to its shape, collectors of P. vancouverensis fossils often call it the "paperclip ammonite" or "candy cane".
- P. haradanuin (Yokoyama)
It also contains one subgenus
Subgenus
In biology, a subgenus is a taxonomic rank directly below genus.In zoology, a subgeneric name can be used independently or included in a species name, in parentheses, placed between the generic name and the specific epithet: e.g. the Tiger Cowry of the Indo-Pacific, Cypraea tigris Linnaeus, which...
, Subptychoceras, which contains one subspecies
Subspecies
Subspecies in biological classification, is either a taxonomic rank subordinate to species, ora taxonomic unit in that rank . A subspecies cannot be recognized in isolation: a species will either be recognized as having no subspecies at all or two or more, never just one...
, S. yubarense. P. pseudogaultinum could reach a length of 100 - 120 mm, while S. yubarense could reach a maximum length of 200 mm.
Description
Polyptychoceras is a heteromorph ammonite, meaning that its shell does not curl up into the tight spiral shape which shells of ammonites from the subclass Ammonoidea typically do.Polyptychoceras shells have an abrupt weight increase after formation of the initial shaft, which represents the shell's automatic balance condition. This would have caused the shell to topple over if on land. The soft body of the animal would have to have been large, in order to keep the falling shaft off of the ground. The body would not have been resistant to the pressing shell.
Although the shafts in the fossils of the shells are usually parallel to each other, small aberrations during each growth stage often caused abrupt constrictions in the shape of the shell.
Life
A Japanese study in 1979 suggested that Polyptychoceras lived and travelled in schools, similarly to modern cuttle fish. Individual fossil specimens of a particular species of Polyptychoceras are frequently found in sediments laid down in the same bed of water, around the SantonianSantonian
The Santonian is an age in the geologic timescale or a chronostratigraphic stage. It is a subdivision of the Late Cretaceous epoch or Upper Cretaceous series. It spans the time between 85.8 ± 0.7 mya and 83.5 ± 0.7 mya...
and Upper Coniacian
Coniacian
The Coniacian is an age or stage in the geologic timescale. It is a subdivision of the Late Cretaceous epoch or Upper Cretaceous series and spans the time between 89.3 ± 1 Ma and 85.8 ± 0.7 Ma...
faunal stage
Faunal stage
In chronostratigraphy, a stage is a succession of rock strata laid down in a single age on the geologic timescale, which usually represents millions of years of deposition. A given stage of rock and the corresponding age of time will by convention have the same name, and the same boundaries.Rock...
s of the Late Cretaceous
Late Cretaceous
The Late Cretaceous is the younger of two epochs into which the Cretaceous period is divided in the geologic timescale. Rock strata from this epoch form the Upper Cretaceous series...
Epoch
Epoch (geology)
An epoch is a subdivision of the geologic timescale based on rock layering. In order, the higher subdivisions are periods, eras and eons. We are currently living in the Holocene epoch...
. Polyptychoceras was probably buoyant, and swam in a slow, somewhat up-and-down locomotion. It also likely preferred living in sheltered parts of deep sea levels, although how deep is uncertain. Subptychoceras yubarense was likely very long like an eel, and preferred a benthic mode of life.
Suggested further reading
- West Coast Fossils: A Guide to the Ancient Life of Vancouver Island by Rolf Ludvigsen and Graham Beard
- Special papers / Nihon Koseibutsu Gakkai; page 29. Published 1984; Original from the University of California
- Geological Abstracts; page 1324. By Geo Abstracts Bibliography; Published 1986, Elsevier/Geo Abstracts
- Memoirs; page 157. By Fukuoka, Japan Kyushu University. Faculty of Science, Hokkaido University Faculty of Engineering; Published 1959
- Memoirs of the Faculty of Science, Kyushu University; pages 117 - 119. By Kyūshū Daigaku Rigakubu; Published 1940
- Ammonite Faunas of the Upper Cretaceous Rocks of Vancouver Island, British Columbia; pages 100 - 101. By J L Usher, Geological Survey of Canada; Published 1952 E. Cloutier, Queen's Printer
External links
- Polyptychoceras in the Paleobiology DatabasePaleobiology Database' is an online resource for information on the distribution and classification of fossil animals, plants, and microorganisms.-History:The Paleobiology Database was founded in 2000. It has been funded by the National Science Foundation and the Australian Research Council...
- Polyptychoceras in the Ammonite Database
- Polyptychoceras at Zipcodezoo.com