''Holcodiscus'' 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 placed in the family Holcodiscidae. Species in this genus were fast-moving nektonic carnivores. The type species of the genus is ''Ammonites caillaudianus''.

Description

Circular to rectangular whorl section; fine, low, straight or flexuous simple or branched ribs, periodically truncated by thin, high, enlarged ribs bearing lateral and ventrolateral tubercles; inner whorls tending to have depressed whorl section and to resemble

Olcostephanus ''Olcostephanus'' is an extinct ammonoid cephalopod genus belonging to the family Olcostephanidae. These fast-moving nektonic carnivores lived during the Cretaceous, from the upper Valanginian to the lower Hauterivian age.Sepkoski, JacSepkoski's ...

.Wright, C. W. with J.H. Callomon and M.K. Howarth (1996), ''Mollusca 4 Revised, Cretaceous Ammonoidea'', vol. 4
in ''

Treatise on Invertebrate Paleontology The ''Treatise on Invertebrate Paleontology'' (or ''TIP'') published by the Geological Society of America and the University of Kansas Press, is a definitive multi-authored work of some 50 volumes, written by more than 300 paleontologists, and co ...

'', Part L (Roger L. Kaesler et el. eds.), Boulder, Colorado: The Geological Society of America & Lawrence, Kansas: University of Kansas Press, p.48.

Species

* ''Holcodiscus caillaudianus'' d'Orbigny 1850 * ''Holcodiscus camelinus'' d'Orbigny 1850 * ''Holcodiscus hauthali'' Paulcke 1907 * ''Holcodiscus tenuistriatus'' Paulcke 1907

Distribution

Fossils of species within this genus have been found in the

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 ...

sediments of Austria, Bulgaria, Chile, Colombia, Czech Republic, Slovakia, France, Italy, Morocco, Spain and Russia.

Notes

References

* Arkell, W.J. ''et al.'', (1957). Mesozoic Ammonoidea Treatise on Invertebrate Paleontology, Part L, Ammonoidea. Geological Society of America and Univ Kansas Press.

External links

* * Cretaceous ammonites Ammonitida genera Desmoceratoidea Ammonites of Europe Early Cretaceous genus first appearances Santonian genus extinctions Barremian life Hauterivian life Cretaceous Italy Fossils of Italy Cretaceous France Fossils of France Fossils of Georgia (country) Cretaceous Spain Fossils of Spain Ammonites of North America Fossils of the United States Ammonites of South America Cretaceous Argentina Fossils of Argentina Cretaceous Colombia Fossils of Colombia {{Ammonitina-stub