''Ancyloceras'' is an extinct
genus
Genus ( plural genera ) is a taxonomic rank used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In the hierarchy of biological classification, genus com ...
of
heteromorph
The Ancyloceratina were a diverse suborder of ammonite most closely related to the ammonites of order Lytoceratina. They evolved during the Late Jurassic but were not very common until the Cretaceous period, when they rapidly diversified and bec ...
ammonite
Ammonoids are a group of extinct marine mollusc animals in the subclass Ammonoidea of the class Cephalopoda. These molluscs, commonly referred to as ammonites, are more closely related to living coleoids (i.e., octopuses, squid and cuttlefish) ...
s found throughout the world during the Lower
Cretaceous
The Cretaceous ( ) is a geological period that lasted from about 145 to 66 million years ago (Mya). It is the third and final period of the Mesozoic Era, as well as the longest. At around 79 million years, it is the longest geological period of th ...
, from the Lower
Barremian
The Barremian is an age in the geologic timescale (or a chronostratigraphic stage) between 129.4 ± 1.5 Ma (million years ago) and 121.4 ± 1.0 Ma). It is a subdivision of the Early Cretaceous Epoch (or Lower Cretaceous Series). It is preceded ...
epoch until the genus extinction during the Lower
Aptian
The Aptian is an age in the geologic timescale or a stage in the stratigraphic column. It is a subdivision of the Early or Lower Cretaceous Epoch or Series and encompasses the time from 121.4 ± 1.0 Ma to 113.0 ± 1.0 Ma (million years ago), a ...
.
[Sepkoski, Jac]
Sepkoski's Online Genus Database – Cephalopoda
/ref>
/ref>
Selected species
*''Ancyloceras audouli'' Astier, 1851
*''Ancyloceras fallauxi'' Uhlig, 1883
*''Ancyloceras mantelli'' Casey, 1960
*''Ancyloceras matheronianum'' d'Orbigny, 1842
*''Ancyloceras vandenheckii'' Astier, 1851[
]
Description
''Ancyloceras'' ammonites have a shell reaching a length of about and a width of about . They are known as heteromorph shaped, with a partly uncoiled shell and the aperture directed toward the coiled part.
Most ammonites are homomorph, as they maintain the same shape throughout the growth, while the ammonites in this genus have uncoiled shells (heteromorph
The Ancyloceratina were a diverse suborder of ammonite most closely related to the ammonites of order Lytoceratina. They evolved during the Late Jurassic but were not very common until the Cretaceous period, when they rapidly diversified and bec ...
or different-shaped ammonites), that would have precluded fast swimming.[
]
Distribution
Fossils of ''Ancyloceras'' species are found in the Cretaceous Barremian Stage (117-113 million year old) marine strata of Europe, Colombia and Morocco.
References
External links
* David L. Clar
Anisoceras and Ancyloceras from the Texas Cretaceous
Journal of Paleontology - Vol. 32, No. 6 (Nov., 1958), pp. 1076-1081
Ancyloceratoidea
Ammonitida genera
Early Cretaceous ammonites of Europe
Cretaceous animals of Africa
Paja Formation
{{Ammonitida-stub