Aptychophora

Simbirskites sp., copyright J.-W. Janzen.

Belongs within: Ammonitida.
Contains: Baculitidae, Oppeliidae, Stephanocerataceae, Perisphinctaceae, Leptoceras, Ancyloceratidae, Brancoceratoidea, Pachydiscidae.

The Aptychophora are a clade within the ammonites characterised by the development of bivalved aptychi, calcified lower jaws that probably functioned as opercula to close the entrance of the shell. Such structures are first known from the lower Toarcian (in the lower Jurassic) among members of the probably paraphyletic Hildocerataceae. Members of the Hildocerataceae possess cornaptychi, with a thin horny outer layer and a thicker mineralised inner layer, and these are probably the plesiomorphic aptychus condition. More derived groups developed alternate aptychus morphologies. The Middle Jurassic to Lower Cretaceous Haplocerataceae possessed lamellaptychi, with strong concentric ribs; members of the Haplocerataceae are also characterised by smooth, typically compressed, discoidal or oxycone shells with falcoid or falcate ribbing. The remaining Aptychophora form a clade with the Stephanocerataceae and Perisphinctaceae as basal members, early members of which possessed a thin-shelled and relatively broad praestriaptychus with weak concentric striae (Engeser & Keupp 2002).

Characters (from Engeser & Keupp 2002): Presence of a calcified lower jaw, both halves attached to each other with a weakly calcified or organic fold. Outer surface with growth lines only. Structure simple in primitive forms, more complex in subordinated groups.

<==Aptychophora
    |  i. s.: Strigogranulaptychus Schweigert 2000 EK02
    |           `--*S. planulati (Quenstedt 1852) [=Granulaptychus planulati] EK02
    |         Baculitidae EK02
    |--Hildocerataceae EK02
    |    |  i. s.: Leioceras Hyatt 1867 [Leioceratinae] EK02
    |    |           `--L. opalinum M79
    |    |--Graphoceratidae EK02
    |    |--Hammatoceratidae EK02
    |    |--Grammoceratinae [Grammoceratidae] EK02
    |    |    |--Dumortieria Haug 1885 EK02
    |    |    |--Grammoceras Hyatt 1867 EK02
    |    |    `--Phlyseogrammoceras Buckman 1901 EK02
    |    |--Sonniniidae [Sonniniinae] EK02
    |    |    |--Dorsetensia Buckman 1892 EK02
    |    |    |--Euhoploceras Buckman 1913 EK02
    |    |    `--Sonninia Bayle 1879 EK02
    |    |         `--S. ‘ovalis’ (Quenstedt 1886) (see below for synonymy) CDH04
    |    `--Hildoceratidae EK02
    |         |--Hildoceras Hyatt 1867 [Hildoceratinae] EK02
    |         `--Harpoceratinae EK02
    |              |--Polyplectus Buckman 1890 EK02
    |              |--Protogrammoceras Spath 1913 EK02
    |              |--Pseudolioceras Buckman 1889 EK02
    |              `--Harpoceras Waagen 1869 H79, EK02
    |--Haplocerataceae EK02
    |    |--Strigoceratidae EK02
    |    |--Haploceratidae EK02
    |    |    |--Glochiceras Hyatt 1900 EK02
    |    |    |--Neolissoceras Spath 1923 EK02
    |    |    |--Pseudolissoceras Spath 1925 [incl. Laevilamellaptychus Trauth 1936] EK02
    |    |    `--‘Haploceras’ Zittel 1870 non Saemann 1853 EK02
    |    |         `--H. elimatum H79
    |    `--Oppeliidae EK02
    `--+--Stephanocerataceae EK02
       `--+--Perisphinctaceae EK02
          `--+--Douveilliceratidae [Douvilleicerataceae] W69
             |    |--Leptoceras EK02
             |    `--Hypacanthoplites K79
             |--Olcostephanidae EK02
             |    |--Olcostephanus Neumayr 1875 EK02
             |    |    `--O. inverselobatus EK02
             |    `--Simbirskites Pavlov 1892 EK02
             |         |  i. s.: S. broodi K79
             |         |         S. decheni K79
             |         |         S. inversum K79
             |         |         S. kleini K79
             |         |         S. morvenae [incl. Perisphinctes kayseri Etheridge 1909 (preoc.)] F71
             |         |         S. progredicus K79
             |         |         S. speetonensis K79
             |         |--S. (Craspedodiscus) K79
             |         |    |--S. (C.) discofalcatus K79
             |         |    `--S. (C.) gottschei K79
             |         `--S. (Milanowskia) K79
             |              |--S. (M.) ihmensis K79
             |              `--S. (M.) staffi Wedekind 1915 K79, EK02
             `--+--Ancyloceratidae EK02
                `--+--Brancoceratoidea EK02
                   |--Hoplitaceae [Hoplitoidea] EK02
                   |    |  i. s.: Metaplacenticeras TLY03
                   |    |           |--M. pacificum K79
                   |    |           `--M. subtilistriatum TLY03
                   |    |--Schloenbachia Neumayr 1875 [Schloenbachiidae] EK02
                   |    |    |--S. coupei [=Ammonites coupei] H04
                   |    |    `--S. varians K79
                   |    |--Placenticeras K79 [Placenticeratidae EK02]
                   |    |    |--P. bidorsatum K79
                   |    |    `--P. syrtale K79
                   |    `--Hoplitidae EK02
                   |         |--Chimbuites K79
                   |         `--‘Hoplites’ Neumayr 1875 nec Hübner 1816 nec Koch 1869 EK02
                   |              |  i. s.: H. lautus K79
                   |              |         H. loricatus K79
                   |              |         H. nitidus K79
                   |              |         H. steinmanni KK08
                   |              |         H. teschensis K79
                   |              `--H. (Hoplites) K79
                   |                   |--H. (H.) dentatus (Sowerby 1821) K79, KK08
                   |                   `--H. (H.) spathi K79
                   `--Pachydiscidae EK02

Sonninia ‘ovalis’ (Quenstedt 1886) [=Ammonites sowerbyi ovalis nec A. alternans ovalis Quenstedt 1845 nec A. psilonotus ovalis Quenstedt 1882 nec A. insignis ovalis Quenstedt 1885] CDH04

*Type species of generic name indicated

REFERENCES

[CDH04] Callomon, J. H., D. T. Donovan & M. K. Howarth. 2004. F. A. Quenstedt’s trinomial nomenclature of Jurassic ammonites. Palaeontology 47 (4): 1063–1073.

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

[F71] Fletcher, H. O. 1971. Catalogue of type specimens of fossils in the Australian Museum, Sydney. Australian Museum Memoir 13: 1–167.

[H04] Haeckel, E. 1899–1904. Kunstformen der Natur. Bibliographisches Institut: Leipzig und Wien.

[H79] Hölder, H. 1979. Jurassic. In: Robison, R. A., & C. Teichert (eds) Treatise on Invertebrate Paleontology pt A. Introduction. Fossilisation (Taphonomy), Biogeography and Biostratigraphy pp. A390–A417. The Geological Society of America, Inc.: Boulder (Colorado), and The University of Kansas: Lawrence (Kansas).

[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. Cretaceous faunas from Zululand and Natal, South Africa. The ammonite subfamily Lyelliceratinae Spath, 1921. African Natural History 4: 57–111.

[M79] Müller, A. H. 1979. Fossilization (taphonomy). In: Robison, R. A., & C. Teichert (eds) Treatise on Invertebrate Paleontology pt A. Introduction. Fossilisation (Taphonomy), Biogeography and Biostratigraphy pp. A2–A78. The Geological Society of America, Inc.: Boulder (Colorado), and The University of Kansas: Lawrence (Kansas).

[TLY03] Tanabe, K., N. H. Landman & Y. Yoshioka. 2003. Intra- and interspecific variation in the early internal shell features of some Cretaceous ammonoids. Journal of Paleontology 77 (5): 876–887.

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