Pachydiscus

Pachydiscus neubergicus, from Antonov.

Belongs within: Pachydiscidae.

Pachydiscus is a genus of ammonites known from the Upper Cretaceous (Campanian to Upper Maastrichtian) worldwide.

Characters (from Wright et al. 1996): Compressed, high-whorled, with flat or convex sides; ribs tending to differentiate into short umbilicals and separate ventrolaterals, the latter tending to be interrupted on venter or to disappear.

<==Pachydiscus Zittel 1884EK02
    |  i. s.: P. colligatusK79
    |         P. epiplectusWCH96
    |         P. grossouvreiK79
    |         P. oldhamiK79
    |         P. subcompressusK79
    |         P. ultimusOZ89
    |--P. (Pachydiscus) [incl. Joaquinites Anderson 1958, Parapachydiscus Hyatt 1900]WCH96
    |    |--*P. (P.) neubergicus (Hauer 1858) (nom. cons.) [=Ammonites neubergicus; incl. A. chrishna Forbes 1846]WCH96
    |    |--P. (P.) compressusWCH96
    |    |--*Joaquinites’ fascicostatus Anderson 1958WCH96
    |    |--P. (P.) gollevillensis (Orbigny 1850)KM08, WCH96 [=Ammonites gollevillensisWCH96, *Parapachydiscus gollevillensisWCH96]
    |    |--P. (P.) jacquotiBRW98
    |    |    |--P. j. jacquotiBRW98
    |    |    `--P. j. australisBRW98
    |    `--P. (P.) llarenaiW69
    `--P. (Neodesmoceras Matsumoto 1947)WCH96
         `--P. (*N.) japonicus Matsumoto 1947WCH96

*Type species of generic name indicated

References

[BRW98] Beesley, P. L., G. J. B. Ross & A. Wells (eds) 1998. Fauna of Australia vol. 5. Mollusca: The Southern Synthesis. Part A. Australian Biological Resources Study: Canberra.

[EK02] Engeser, T., & H. Keupp. 2002. Phylogeny of the aptychi-possessing Neoammonoidea (Aptychophora nov., Cephalopoda). Lethaia 35: 79–96.

[K79] Kauffman, E. G. 1979. Cretaceous. In: Robison, R. A., & C. Teichert (eds) Treatise on Invertebrate Paleontology pt A. Introduction. Fossilisation (Taphonomy), Biogeography and Biostratigraphy pp. A418–A487. The Geological Society of America, Inc.: Boulder (Colorado), and The University of Kansas: Lawrence (Kansas).

[KM08] Klinger, H. C., & N. Malchus. 2008. The first record of Agerostrea ungulata (von Schlotheim, 1813) (Bivalvia: Ostreoidea) from the Upper Maastrichtian of KwaZulu, South Africa, with a discussion of its distribution in southeast Africa and Madagascar. African Natural History 4: 11–16.

[OZ89] Olivero, E. B., & W. J. Zinsmeister. 1989. Large heteromorph ammonites from the Upper Cretaceous of Seymour Island, Antarctica. Journal of Paleontology 63 (5): 626–636.

[W69] Wiedmann, J. 1969. The heteromorphs and ammonoid extinction. Biological Reviews 44: 563–602.

[WCH96] Wright, C. W., J. H. Calloman & M. K. Howarth. 1996. Treatise on Invertebrate Paleontology pt L. Mollusca 4, revised vol. 4. Cretaceous Ammonoidea. The Geological Society of America, Inc.: Boulder (Colorado), and The University of Kansas: Lawrence (Kansas).

Leave a comment

Your email address will not be published. Required fields are marked *