''Australiceras'' is an extinct

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) ...

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 ...

from the upper part of the Early Cretaceous,

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 ...

stage, included in the family

Ancyloceratidae Ancyloceratidae is a family of heteromorphic Ammonitida, ammonites that lived during the Early Cretaceous. Their shells begin as a loose spiral with whorls not touching which then turns into a straight shaft that ends in a J-shape hook or bend ...

Description

''Australiceras'' has an evolute shell, coiled with all whorls showing in keeping with its inclusion in the

Ancyloceratida 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 beca ...

. The inner, early, whorls bear ribs that alternate between those that are smooth and those the bear stout blunt or conical tubercles. Ribs on the outer whorls become free of tubercles and end up all smooth. ''Australiceras'' bears some resemblance to ''

Tropaeum ''Tropaeum'' is an extinct genus of ammonites found throughout the oceans of the world during the Early Cretaceous. As with many other members of the family Ancyloceratidae, there was a trend among species within this genus to uncoil somewhat, ...

'' and ''

Balearites ''Balearites'' is an extinct ancyloceratin genus included in the family Crioceratitidae, subclass Ammonoidea, from the Upper Hauterivian. The shell, or conch, of ''Balearites'' is planispiral; whorls compressed, fairly flat sided, barely in co ...

'', both related genera. The type species is ''Australiceras jacki''.

References

;Notes ;Bibliography * W. J. Arkell et al. 1957. Mesozoic Ammonoidea, Treatise on Invewrtebrate Paleontology, Part L. Geological Society of America, R.C.Moore, (ed) * F. W. Whitehouse. 1926. "The Cretaceous Ammonoidea of Eastern Australia", ''Memoirs of the Queensland Museum'' 8(3):195-242. Ammonitida genera Cretaceous ammonites Cretaceous animals of Africa Aptian life Ancyloceratoidea {{Ammonite-stub