Leptoceras

Cheloniceras sp., from here.

Belongs within: Aptychophora.
Contains: Scaphitoidea.

Leptoceras is a genus of small, loosely coiled ammonites known from the Lower Cretaceous ((Upper Berriasian to Valanginian) (Wright et al. 1996). Wiedmann (1969) depicted this genus as ancestral to a number of later ammonite lineages, including both heteromorphic and regular forms.

<==Leptoceras
    |--L. studeri W69
    `--+--L. pumilum W69
       |--+--Paraspiticeras W69
       |  |--Trochleiceras W69
       |  |--Acanthohoplites reesidei W69, K79
       |  `--+--+--Astiericeras W69
       |     |  `--Douvilleiceras W69
       |     |       |--D. clementianum (d’Orbigny 1841) KK08a
       |     |       |--D. inaequinodum (Quenstedt 1849) KK08a
       |     |       |--D. mammillatum (von Schlotheim 1813) KK08a
       |     |       |--D. orbignyi Hyatt 1903 KK08a
       |     |       `--D. scabrosum Casey 1962 KK08a
       |     `--Cheloniceras W69
       |          |  i. s.: C. martinoides K79
       |          |         C. subcornuerianum K79
       |          |         C. subnodocostatum K79
       |          |         C. tschernyschewi K79
       |          |--C. (Cheloniceras) K79
       |          |    |--C. (C.) meyendorfi K79
       |          |    `--C. (C.) parinodum K79
       |          `--C. (Epicheloniceras) K79
       |               |--C. (E.) buxtorfi K79
       |               |--C. (E.) debile K79
       |               `--C. (E.) gracile K79
       `--+--Scaphitoidea W69
          `--Turrilitaceae [Turriculacea] W69
               |--Diplomoceratidae EK02
               |    |--Scalarites Wright & Matsumoto 1954 EK02
               |    `--Diplomoceras Hyatt 1900 OZ89
               |         |--*D. cylindraceum (Defrance 1806) [=Baculites cylindraceae] OZ89
               |         |--D. australe OZ89
               |         |--‘Hamites’ elatior (n. d.) OZ89
               |         |--D. lambi Spath 1953 OZ89
               |         |--D. maximum Olivero & Zinsmeister 1989 OZ89
               |         |--D. notabile OZ89
               |         `--D. (Glyptoxoceras) subcompressum W69
               `--Turrilitidae EK02
                    |  i. s.: Turrilites Lamarck 1801 BR05
                    |           |--T. acutus K79
                    |           `--T. costatus KK08b
                    |         Pseudhelicoceras convolutum W69
                    |         Helicoceras d’Orbigny 1842 W77
                    |           |--H. mortoni W77
                    |           `--H. pariense White 1877 W77
                    |--Algerites W69
                    |--+--Hyphantoceras reussianum W69, K79
                    |  `--Neocrioceras W69
                    `--+--Proturrilitoides W69
                       `--+--Bostrychoceras polyplocum W69, K79
                          |--Cirroceras W69
                          |--Jouaniceras W69
                          |--Anaklinoceras W69
                          `--Axonoceras W69
                               |--A. compressum K79
                               |--A. multicostatum K79
                               `--A. pingue K79

*Type species of generic name indicated

REFERENCES

[BR05] Bouchet, P., & J.-P. Rocroi. 2005. Classification and nomenclator of gastropod families. Malacologia 47 (1–2): 1–397.

[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).

[KK08a] Kennedy, W. J., & H. C. Klinger. 2008a. Cretaceous faunas from Zululand and Natal, South Africa. The ammonite subfamily Lyelliceratinae Spath, 1921. African Natural History 4: 57–111.

[KK08b] Kennedy, W. J., & H. C. Klinger. 2008b. Cretaceous faunas from Zululand and Natal, South Africa. The ammonite family Forbesiceratidae Wright, 1952. African Natural History 4: 117–130.

[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.

[W77] White, C. A. 1877. Report upon the invertebrate fossils collected in portions of Nevada, Utah, Colorado, New Mexico, and Arizona, by parties of the expeditions of 1871, 1872, 1873, and 1874. U.S. Geographical Surveys West of the One Hundredth Meridian 4 (1): 1–219, pls 1–21.

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