Spathognathodus

 Spathognathodus sp., from Louisville Fossils.

Belongs within: Spathognathodontidae.

Spathognathodus has been recognised as a genus of conodonts dating from the Lower Silurian to the Middle Triassic (Hass 1962). In the form-taxon sense it corresponds to the Pa elements of more complete apparatus. The type species S. primus is known from the Middle Silurian of North America (Hass 1962).

Bardashev et al. (2002) suggested that S. postexcelsus probably represented the ancestor of the Lower Devonian genus Pseudogondwania, which possesses a narrow platform that may or may not reach the posterior end, ornamented by two lateral rows of nodes, and a free anterior blade bearing five to seven high denticles in an arched row.

Characters (from Hass 1962, for P1 element only): Essentially straight in oral view; denticles along midline closely set, may be flanked laterally by one or more denticles; oral surface of lips or lateral expansions of pulp cavity may support denticles.

<==Spathognathodus Branson & Mehl 1941 [=Spathodus Brandon & Mehl 1933 non Boulenger 1900]H62
    |--S. frankenwaldensisBWZ02
    `--+--S. optimus Moskalenko 1966 [=Pandorinellina optima]BWZ02
       `--+--S. postexcelsus (Wang & Ziegler 1983)BWZ02
          `--Pseudogondwania Bardashev, Weddige & Ziegler 2002BWZ02
               |--P. klapperi Bardashev, Weddige & Ziegler 2002BWZ02
               `--+--+--*P. kindlei (Lane & Ormiston 1979) [=Eognathodus sulcatus kindlei]BWZ02
                  |  `--P. ethingtoni Bardashev, Weddige & Ziegler 2002BWZ02
                  `--+--P. clarki Bardashev, Weddige & Ziegler 2002BWZ02
                     `--P. murphyi Bardashev, Weddige & Ziegler 2002BWZ02
Spathognathodus incertae sedis:
  *S. primus (Branson & Mehl 1933) [=*Spathodus primus]H62
  S. anteposicornisN79
  S. bidentatusN79
  S. coloradoensisT85
  S. costatusN79
  S. ellisoni Merrill 1973L73
  S. johnsoniN79
  S. jugosusH62
  S. minutus (Ellison 1941)L73
  S. stabilisBWZ02
  S. steinhornensisN79

*Type species of generic name indicated

References

[BWZ02] Bardashev, I. A., K. Weddige & W. Ziegler. 2002. The phylomorphogenesis of some Early Devonian platform conodonts. Senckenbergiana Lethaea 82: 375–451.

[H62] Hass, W. H. 1962. Conodonts. In: Moore, R. C. (ed.) Treatise on Invertebrate Paleontology pt W. Miscellanea: Conodonts, Conoidal Shells of Uncertain Affinities, Worms, Trace Fossils and Problematica pp. W3–W69. Geological Society of America, and University of Kansas Press.

[L73] Lane, H. R. 1973. Lectotype or neotype: a problem for ICZN clarification. Systematic Zoology 22 (3): 324–325.

[N79] Norris, A. W. 1979. Devonian in the Western Hemisphere. In: Robison, R. A., & C. Teichert (eds) Treatise on Invertebrate Paleontology pt A. Introduction. Fossilisation (Taphonomy), Biogeography and Biostratigraphy pp. A218–A253. The Geological Society of America, Inc.: Boulder (Colorado), and The University of Kansas: Lawrence (Kansas).

[T85] Thayer, D. W. 1985. New Pennsylvanian lepospondyl amphibians from the Swisshelm Mountains, Arizona. Journal of Paleontology 59 (3): 684–700.

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