Calycoceras spinosum, from here.

Belongs within: Acanthoceratidae.

Calycoceras is an Upper Cretaceous (Cenomanian) genus of evolute ammonites with depressed whorls. Several subgenera are recognised with representatives of the type subgenus being medium-sized to large forms with more or less distant and coarse ribs, and all tubercles except the umbilicals normally absent in middle growth (Wright et al. 1996).

Characters (from Wright et al. 1996): Rather evolute, with whorl section depressed and subcircular, oval, polygonal, or subquadrate; ribs strong, generally straight, continuous over rounded or flat but not concave venter; on early whorls at least umbilical, ventrolateral, siphonal, and, in most specimens, midlateral tubercles; in multituberculate forms umbilical tubercle more prominent than midlateral; tubercles may disappear with age and may or may not be rejuvenated on last part of shell. Marked dimorphism in size apparently general.

<==Calycoceras Hyatt 1900 [=Metacalycoceras Spath 1926 (nom. rej.)]WCH96
    |--*C. (Calycoceras) naviculare (Mantell 1822)WCH96 (see below for synonymy)
    |--C. (Gentoniceras Thomel 1972) [incl. Subeucalycoceras Thomel 1972]WCH96
    |    |--C. (*G.) gentoni (Brongniart in Cuvier & Brongniart 1822) [=Ammonites gentoni]WCH96
    |    `--‘Acanthoceras’ sarthacense Bayle 1878 [incl. A. baylei Pervinquière 1907, *Subeucalycoceras baylei]WCH96
    |--C. (Hourcqiceras Collignon 1939)WCH96
    |    `--C. (*H.) hourcqi Collignon 1939WCH96
    |--C. (Newboldiceras Thomel 1972) [incl. Mourreiceras Thomel 1972, Pseudacanthoceras Thomel 1972]WCH96
    |    |--C. (N.) asiaticum (Jimbo 1894) (see below for synonymy)WCH96
    |    |--‘Newboldiceras (*Mourreiceras)’ mourrei Thomel 1972WCH96
    |    `--‘Acanthoceras’ tapara Wright 1963 [=*Pseudacanthoceras tapara]WCH96
    `--C. (Proeucalycoceras Thomel 1972) [incl. Haugiceras Thomel 1972]WCH96
         |--C. (*P.) besairiei Collignon 1937 [=C. (Eucalycoceras) besairiei]WCH96
         `--‘Acanthoceras’ haugi Pervinquière 1907 [=*Haugiceras haugi]WCH96
Calycoceras incertae sedis:
  C. andranovaritelenseK79
  C. bouleiK79
  C. canitaurinumK79
  C. guerangeriWCH96
  C. jeannetiK79
  C. latelobatumK79
  C. leonenseK79
  C. orientaleK79
  C. spinosumK79
  C. stoliczkaiK79
  C. tarrantenseK79

*Calycoceras (Calycoceras) naviculare (Mantell 1822)WCH96 [=Ammonites navicularisWCH96, Acanthoceras naviculareKK08, *Metacalycoceras naviculareWCH96]

Calycoceras (Newboldiceras) asiaticum (Jimbo 1894) [=Acanthoceras asiaticum; incl. A. newboldi Kossmat 1897, Calycoceras (*Newboldiceras) newboldi]WCH96

*Type species of generic name indicated


[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).

[KK08] Kennedy, W. J., & H. C. Klinger. 2008. Hypermorphosis in Salaziceras, a Cretaceous ammonite, from Madagascar. African Natural History 4: 113–116.

[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).

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