Polyptychoceras

Taxobox
name = "Polyptychoceras"
fossil_range = Late Cretaceous
regnum = Animalia
phylum = Mollusca
classis = Cephalopoda
subclassis = Ammonoidea
ordo =
superfamilia =
genus = "Polyptychoceras"
genus_authority = Yabe, 1927
type_species =
subgenus=Subptychoceras
subgenus_authority=Yabe
subdivision_ranks=Species
subdivision=
* †"P. mihoense"
* †"P. pseudogaultinum"
* †"P. haradanuin"
* †"P. obatai"
* †"P. obliquecostatum"
* †"P. subunduratum"
* †"P. vancouverensis"
* †"P. obstrictum"

"Polyptychoceras" is an extinct genus of ammonite from the Late Cretaceous of Asia, Europe, and Northcite web |url=http://northislandexplorer.com/fossils/cretaceous/polyptychoceras.htm |title=Cretaceous Ammonite: Polyptychoceras |publisher=northislandexplorer.com |accessdate=2008-07-09] and South America. It was first named by Hisakatsu Yabe in 1927,cite web |url=http://www.journalarchive.jst.go.jp/jnlpdf.php?cdjournal=pjab1977&cdvol=55&noissue=3&startpage=115&lang=en&from=jnlabstract |title=An Interesting Mode of Occurrence of Polyptychoceras |publisher=By Tatsuro Matsumoto and Mitsutoshi Nihongi; Japan Academy |date=1979 |accessdate=2008-07-09] and contains eight species and a subgenus, "Subtychoceras", which contains one species.

pecimens

*"P. mihoense"
*"P. haradanuin" (Yokoyama)
*"P. obatai"
*"P. obliquecostatum"
*"P. subunduratum"
*"P. obstrictum" (Jimbo)
*"P. vancouverensis" located around the Trent River and the 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, "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.

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. cite web |url=http://www.ebel-k.de/Ammoniten/Lifestyle1/Heteromorphs/heteromorphs.html |title=Heteromorphs |ppublisher=www.ebel-k.de |accessdate=2008-07-10] This would have caused the shell to topple over if on land. The soft body of the animal would have had 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 abruptness in the shape of the shell. ["Ammonoid Paleobiology" (Topics in Geobiology) by Neil H. Landman, Kazushige Tanabe, and Richard Arnold Davis; page 224. Published 1996 Springer. ISBN 0306452227 Retrieved on 2008-05-02]

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 Santonian and Upper Coniacian faunal stages 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.

References

uggested 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

* [http://paleodb.org/cgi-bin/bridge.pl?action=checkTaxonInfo&taxon_no=15431 "Polyptychoceras"] in the Paleobiology Database
* [http://www.um.u-tokyo.ac.jp/cgi-bin/umdb/ammonite?S=601&C=30 "Polyptychoceras"] in the Ammonite Database
* [http://zipcodezoo.com/Key/Polyptychoceras_Genus.asp "Polyptychoceras"] at Zipcodezoo.com