''Asymptoceras'' is a genus of
aipoceratids (
Nautiloidea
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 species. ...
) similar to ''
Aipoceras
''Aipoceras'' is a genus of loosely coiled aipoceratid 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 ...
'' but tightly coiled and with only part of the body chamber divergent from the previous
whorl
A whorl ( or ) is an individual circle, oval, volution or equivalent in a whorled pattern, which consists of a spiral or multiple concentric objects (including circles, ovals and arcs).
Whorls in nature
File:Photograph and axial plane floral ...
. Shell
evolute
In the differential geometry of curves, the evolute of a curve is the locus of all its centers of curvature. That is to say that when the center of curvature of each point on a curve is drawn, the resultant shape will be the evolute of that curv ...
, expanding fairly rapidly;
umbilicus open,
perforate
A perforation is a small hole in a thin material or web. There is usually more than one perforation in an organized fashion, where all of the holes collectively are called a ''perforation''. The process of creating perforations is called perfor ...
; whorl section ovoid to
subquadrate.
''Asymptoceras'' is known from
Mississippian (Lower Carboniferous) sediments in
Europe
Europe is a large peninsula conventionally considered a continent in its own right because of its great physical size and the weight of its history and traditions. Europe is also considered a Continent#Subcontinents, subcontinent of Eurasia ...
and
North America
North America is a continent in the Northern Hemisphere and almost entirely within the Western Hemisphere. It is bordered to the north by the Arctic Ocean, to the east by the Atlantic Ocean, to the southeast by South America and the Car ...
.
References
* Bernard Kummel, 1964. Nautiloidea - Nautilida; Treatise on Invertebrate Paleontology, Part K. Geological Society of America.
''Asymptoceras''i
Fossilworks
Prehistoric nautiloid genera
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