''Wutinoceras'' is a
genus
Genus ( plural genera ) is a taxonomic rank used in the biological classification of living and fossil organisms as well as viruses. In the hierarchy of biological classification, genus comes above species and below family. In binomial nom ...
of now extinct
nautiloid
Nautiloids are a group of marine cephalopods (Mollusca) which originated in the Late Cambrian and are represented today by the living ''Nautilus'' and '' Allonautilus''. Fossil nautiloids are diverse and speciose, with over 2,500 recorded specie ...
cephalopods of the
Wutinoceratidae family. It exhibits
orthoconic
An orthocone is an unusually long straight shell of a nautiloid cephalopod.; During the 18th and 19th centuries, all shells of this type were named '' Orthoceras'', creating a wastebasket taxon, but it is now known that many groups of nautiloids ...
actinocerids with ventral
siphuncles composed of broadly expanded segments.
[Memoir 2, Studies of the Actinocerida, New Mexico Bureau of Mines and Mineral Resources][Memoir 19, The First Great Expansion of the Actinoceroids, New Mexico Bureau of Mines and Mineral Resources]
Distinguishing characteristics
''Wutinoceras'', as with its family the Wutinoceratidae, has a
reticulate
Reticulation is a net-like pattern, arrangement, or structure.
Reticulation or Reticulated may refer to:
* Reticulation (single-access key), a structure of an identification tree, where there are several possible routes to a correct identificati ...
d canal system within the
siphuncle, distinguishing it from later forms with arcuate canal systems. Septal necks, components of the siphuncle that project from the back side of the septa, are cyrtochoanitic (outwardly curved) and may be recumbent. Connecting rings are thick, reflective of the ancestral form.
Varieties
The three varieties of ''Wutinoceras'' are based on the form of the siphuncle, and each contains a number of species. These have not been ascribed to subgenera. They include those with broad segments and strongly recumbent brims to the septal necks; those with large segments and rings free ventrally; and those with small segments in which the brims on the dorsal side are sometimes free.
[ The genotype ''Wutinoceras foerste'', which comes from northeast China (]Manchuria
Manchuria is an exonym (derived from the endo demonym " Manchu") for a historical and geographic region in Northeast Asia encompassing the entirety of present-day Northeast China (Inner Manchuria) and parts of the Russian Far East (Outer M ...
), is of the second variety.
Distribution
''Wutinoceras'' species of the broad-segment variety are found in Newfoundland, Oklahoma, and Tasmania; those of the large-segment variety are found in Utah, Nevada, Newfoundland, and Manchuria. Those of the small-segment variety have only been found in Nevada.[ unless new species described][Memoir 28, New American Wutinoceratidae .... New Mexico Bureau of Mines and Mineral Resources] from elsewhere can be included.
Phylogeny
''Wutinoceras'' may have its origin in the primitive actinocerid ''Georgina'' from the upper Lower Ordovician of Northern Australia and east Asia[Memoir 44, Nautiloids and their descendants: cephalopod classification in 1986. New Mexico Bureau of Mines and Mineral Resources] although its exact ancestor remains elusive. ''Wutinoceras'' was once thought to be derived from '' Polydesmia''[ from northern China, which was later)][ found to come from beds that overlie those with ''Wutinoceras'', thereby precluding the possibility.
''Wutinoceras'' gave rise to ''Cyrtonybyoceras'' with the development of a curved, cyrtoconic shell and to '' Adamsoceras'' with the development of a more narrow siphuncle.][ ''Wutinoceras'' is also the ancestor of the Armenoceratidae which gave rise in the later Middle Ordovician to '' Actinoceras'' and '' Gonioceras''
]
References
{{Taxonbar, from=Q8039378
Actinocerida
Prehistoric nautiloid genera