Gatunek typowy
Pseudopolygnathus prima Branson et Mehl, 1934 from the Tournaisian of Missouri.

Opis

Diagnosis. —
Elementss p with more or less elaboratedic rion (transverse ribs and tubercles of the same height as the main row of denticles), other elements of the apparatus of generalized polygnathid morphology, robust oz elements may develop a narrow platform.

Icrion in P1 elements composed of rows of tubercles and frequently a longitudinal ridge, basal cavity wide and shallow.

Remarks. —
The type species of Pseudopolygnathusis closely similar and undoubtedly represents the same low-rank evolutionary branch as the type species of BispathodusM iiller, 1962- Spathoduss pinulicostatusB ranson,1 934.These somewhat unfortunate choices of type species that are not typical for the widely accepted concepts of their own genera make distinction between them quite unclear. There seems to be no way to formulate really useful diagnoses for these genera if Pseudopolygnathus encloses species either with icrion or platform and Bispathodus species without any modifications of the oral surface, with additional tubercles at the base or with a wide icrion. In such a situation the most reasonable solution would be to synonymize the two genera and restrict the use of redefined Pseudopolygnathus to species with a well developed icrion in the sp elements. Those with a platform or lacking any modifications of the occlusal surface of the sp elements should then beplaced under other generic names.

The Devonian species attributed here were classified in Bispathodus Müller, 1962, although its type species Spathodus spinulicostatus E. R. Branson, 1934 is of Early Carboniferous age. Its holotype, similar to that of S. costatus, is probably the end member of the variability range of the co-occuring type species of Pseudopolygnathus, P. primus, as suggested by samples from elsewhere. Whatever is the real nature of this specimen, these genera are clearly closely related and there is no way to distinguish them in a satisfactory way.
The icrion developed independently in the branch of P. jugosus and P. ziegleri from the ancestral situation of P. stabilis. However, P. ostrovkensis, with its robust and wide icrion, appears earlier at Kowala than P. jugosus, much less advanced in this respect. Perhaps Pseudopolygnathus, as understood here, is truly polyphyletic and the P. jugosus lineage should be classified in Dasbergina.

Synonimy

Zasięg czasowy

Literatura

Dzik, J. 1997. Emergence and succession of Carboniferous conodont and ammonoid communities in the Polish part of the Variscan sea. Acta Palaeontologica Polonica 42, 57-170.

Dzik, J. 2006. The Famennian "Golden Age" of conodonts and ammonoids in the Polish part of the Variscan sea. Palaeontologia Polonica 63, 1-359.