Steinkern of Pelagiella, from Landing et al. (2002).

Belongs within: Gastropoda.
Contains: Euphemitinae, Tropidodiscidae, Pterothecidae, Knightitinae, Bellerophontinae, Bucaniinae, Sinuitidae.

The name ‘Amphigastropoda’ has been used for an assemblage of planispiral or cap-shaped, mostly Palaeozoic molluscs. Primarily centered around the Bellerophontoidea, other groups that have been included in the Amphigastropoda by various authors include the Pelagielliformes, Cyrtolitidae and Tryblidiidae. The grouping was originally proposed on the basis that these animals were gastropod-like but untorted; however, studies of muscle scars the genus Bellerophon itself indicate that it, at least, underwent torsion, and the Amphigastropoda in the broad sense is probably a polyphyletic assemblage (Peel 1972).

The Bellerophontidae were an Ordovician to Triassic family of coiled molluscs. They were superficially similar to small nautiloids with a deep sinus or slit at the aperture on the outer side of the coil. The umbilicus was narrow or absent, and the shell was ornamented by prominent growth lines (Knight et al. 1960). Most authors have considered the bellerophontids as basal (probably stem-)gastropods, though there is some debate on whether they underwent torsion like modern gastropods.

<==Bellerophontoidea [Amphigastropoda, Bellerophontida, Integridorsata, Terebridorsata]BR17
    |  i. s.: Bucanopsina calypsoW01
    |         EuphemitidaeBR05
    |           |--EuphemitinaeBR05
    |           `--Paleuphemites Horný 1962 [Paleuphemitinae]BR05
    |                `--*P. petrboki Horný 1962BR17
    |         Tremanotus Hall 1865BR17 (see below for synonymy)
    |           |--*T. alpheus (Hall 1865)BR17 [=Porcellia alpheusBR17, *Gyrotrema alpheusKC60, *Trematonotus alpheusKC60]
    |           `--T. maideni Etheridge 1887RJ76
    |--Eobucania Kobayashi 1955W01, KC60
    |    |--*E. pulchra Kobayashi 1955KC60
    |    `--E. mexicana Yochelson 1968TTE93
       `--+--+--‘Eobucania’ bohemicaW01
          |  `--PeelerophonW01
          |       |--P. mergliW01
          |       `--+--P. oehlertiW01
          |          `--Modestospira Yochelson 1964W01, RJ76
          |               `--M. poulseniW01
          `--+--Temnodiscus Koken 1896W01, KC60 [=Cyrtolitina Ulrich in Ulrich & Scofield 1897KC60; Temnodiscidae, Temnodiscinae]
             |    |--*T. lamellifer (Lindström 1884) [=Cyrtolites lamellifer, *Cyrtolitina lamellifer]KC60
             |    |--T. disciformis Hynda 1983D94
             |    `--T. nitidulaW01
             `--+--Kokenospira Bassler 1915W01, KC60 [=Kokenia Ulrich & Scofield 1897 non Holzapfel 1895KC60]
                |    |--*K. esthona (Koken 1889) [=Bucaniella esthona]KC60
                |    `--K. subglobosa Hynda 1983D94
                   |  |  `--BellerophontidaeBR05
                   |  |       |--KnightitinaeBR05
                   |  |       |--BellerophontinaeW01
                   |  |       |--Bucanopsis Ulrich 1897BR05 [=Bucaniopsis Reed 1921KC60; Bucanopsinae]
                   |  |       |    |--*B. carinifera Ulrich 1897BR17 [=*Bucaniopsis cariniferaKC60]
                   |  |       |    `--B. similisW01
                   |  |       `--Cymbularia Koken 1896 [Cymbulariidae, Cymbulariinae]BR05
                   |  |            |--*C. cultrijugata (Roemer 1876) [=Bellerophon cultrijugatus]BR17
                   |  |            |--C. bullatusW01
                   |  |            `--C. galeata Koken 1896KC60
                   |  `--+--Tetranota Ulrich & Scofield 1897W01, KC60
                   |     |    |--T. conspicuaW01
                   |     |    `--+--T. obsoletaW01
                   |     |       `--+--*T. bidorsata (Hall 1847)KC60, W01, KC60 [=Bucania bidorsataKC60]
                   |     |          `--T. sexcarinataW01
                   |     `--Bucanellidae [Bucanellinae, Bucaniellidae, Bucaniellinae]BR05
                   |          |--Bucanella Meek 1871BR05 [=Bucaniella Fischer 1885BR05]
                   |          |    `--*B. nana Meek 1871 [=*Bucaniella nana]KC60
                   |          |--Owenella Ulrich & Scofield 1897KC60
                   |          |    `--*O. antiquata (Whitfield 1878) [=Bellerophon antiquatus]KC60
                   |          |--Pharetrolites Wenz 1943KC60
                   |          |    `--*P. pharetra (Lindström 1884) [=Cyrtolites pharetra]KC60
                   |          `--Tritonophon Öpik 1953W01, KC60
                   |               `--T. peeliW01
                      |    |--BucaniinaeBR05
                      |    |--Salpingostoma Roemer 1876 (see below for synonymy)BR05
                      |    |    |  i. s.: *S. megalostoma (Eichwald 1840) [=Bellerophon megalostoma]KC60
                      |    |    |--S. carnatumW01
                      |    |    `--+--S. buelliW01
                      |    |       `--S. kentuckyenseW01
                      |    `--PlectonotinaeBR05
                      |         |--Boucotonotus Frýda & Manda 1997 [Boucotonotini]BR05
                      |         |    `--*B. snajdri (Horný 1963) [=Plectonotus snajdri]BR17
                      |         `--Plectonotus Clarke 1899 [Plectonotini]BR05
                      |              `--*P. derbyi Clarke 1899 [=Bucanella (*Plectonotus) derbyi]KC60

Salpingostoma Roemer 1876 [Salpingostomatidae, Salpingostomatides, Salpingostomatinae, Salpingostominae]BR05

Tremanotus Hall 1865BR17 [=Gyrotrema Lindström 1884KC60, Trematonotus Fischer 1885BR05; incl. Tremagyrus Perner 1903KC60; TremanotidaeBR05, Tremanotinae, Trematonotidae]

*Type species of generic name indicated


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

[BR17] Bouchet, P., J.-P. Rocroi, B. Hausdorf, A. Kaim, Y. Kano, A. Nützel, P. Parkhaev, M. Schrödl & E. E. Strong. 2017. Revised classification, nomenclator and typification of gastropod and monoplacophoran families. Malacologia 61 (1–2): 1–526.

[D94] Dzik, J. 1994. Evolution of ‘small shelly fossils’ assemblages of the early Paleozoic. Acta Palaeontologica Polonica 39 (3): 247–313.

[KC60] Knight, J. B., L. R. Cox, A. M. Keen, R. L. Batten, E. L. Yochelson & R. Robertson. 1960. Gastropoda: systematic descriptions. In: Moore, R. C. (ed.) Treatise on Invertebrate Paleontology pt I. Mollusca 1: Mollusca—General Features, Scaphopoda, Amphineura, Monoplacophora, Gastropoda—General Features, Archaeogastropoda and some (mainly Paleozoic) Caenogastropoda and Opisthobranchia pp. I169–I331. Geological Society of America, and University of Kansas Press.

[RJ76] Runnegar, B., & P. A. Jell. 1976. Australian Middle Cambrian molluscs and their bearing on early molluscan evolution. Alcheringa 1 (2): 109–138.

[TTE93] Tracey, S., J. A. Todd & D. H. Erwin. 1993. Mollusca: Gastropoda. In: Benton, M. J. (ed.) The Fossil Record 2 pp. 131–167. Chapman & Hall: London.

[W01] Wagner, P. J. 2001. Gastropod phylogenetics: progress, problems and implications. Journal of Paleontology 75 (6): 1128–1140.

Leave a comment

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