''Astreptoceras'' is an extinct upper Cretaceous

ammonoid 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) ...

cephalopod named by Henderson in 1970. Fossils belonging to this genera have been found in Antarctica and New Zealand. The only described species is ''Astreptoceras zelandicum'' (Marshall, 1926). It is a small heteromorph ammonite with almost circular cross-section of the shell. Shell has probably only one straight shaft that is initially without ribs and constrictions. At diameter of about 2 mm there appears first constrictions and at late growth stages, these can be preceded by a collar and shallow secondary constriction. Weak ribs occurs at late growth stages.Henderson, R.A. 1970 Ammonoidea from the Mata Series (Santonian-Maastrichtian) of New Zealand. Special papers in palaeontology, 6: 81 p.

References

*Nomenclator Zoologicu

*Sepkoski's list of cephalopod gener

Cretaceous ammonites Fossils of Antarctica Campanian life {{Ammonite-stub