''Anapachydiscus'' is an extinct cephalopod genus from the Upper Cretaceous,

Santonian The Santonian is an age in the geologic timescale or a chronostratigraphic stage. It is a subdivision of the Late Cretaceous Epoch or Upper Cretaceous Series. It spans the time between 86.3 ± 0.7 mya (million years ago) and 83.6 ± 0.7 mya. The ...

Maastrichtian The Maastrichtian () is, in the ICS geologic timescale, the latest age (uppermost stage) of the Late Cretaceous Epoch or Upper Cretaceous Series, the Cretaceous Period or System, and of the Mesozoic Era or Erathem. It spanned the interval from ...

of Europe, Africa, Madagascar, S.India, N Z, Calif. Mexico, Argentina, and the Antarctic belonging to the

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) ...

family

Pachydiscidae Pachydiscidae is a family of middle and upper Cretaceous ammonites in the superfamily Desmoceratoidea. Morphology Pachydiscidae species are moderate to large in size, evolute to rather involute, and vary in section from inflated and depressed to ...

. ''Anapachydiscus'' has a rather involute shell with a broad to moderately compressed whorl section. Early whorls smooth, intermediary develop straight or slightly curved, radial ribs that thicken toward the umbilicus. Outer whorls may again be smooth, or have coarse ribs so as to resemble ''

Eupachydiscus ''Eupachydisus'' is a large, coarse-ribbed Pachydiscid ammonite genus from the Upper Cretaceous, found in Coniacian to Campanian age strata in Europe, Madagascar, Japan, and British Columbia. The whorl section in ''Eupachydiscus'' is inflated ...

''.

References

*Treatise on invertebrate Paleontology, Part L, Mollusca 4. Mesozoic Ammonoidea. Geological Society of America and Univ. Kansas Press (1957)
''Anapachydiscus''-Paleodb
5/02/11 Late Cretaceous ammonites of North America Coniacian genus first appearances Maastrichtian genus extinctions Desmoceratoidea Ammonitida genera {{Ammonitina-stub