Pseudopolygnothus primus (Branson & Mehl, 1934) - pseudopolygnathids with icrion and gnathodid from the Toumaisian Wapnica beds of Dzikowiec.

Diagnoza

The sp elements of this species are characterised by an occlusal area ornamentation ofthe icrion type, with lateral denticles of the same height as those of the main row of the blade and connected with them by transverse ribs. In Kowala the oldest sample with elements of this type, having denticulation on both sides of the blade at adult stages,is Ko-53 collected 15.2 m below the top ofthe section.Juvenile specimens are present of P.  'Bispathodus') costatus morphology, and adults are still narrow, with a long smooth furrow separating the posterior row of denticles (there is rather a platform than icrion at this side of the element). The sample Ko-56, 0.6 m below, contains only elements with the icrion developing on one side of the blade even in large specimens. In samples taken higher above, the sp elements are more robust at comparable histogenetic stages and more triangular in appearance. This may reflect some evolutionary change but the great population variability and relatively small sample sizes do not allow one to document it biometrically.
The populations of the species strongly differ in sp elements morphology from those of the lineage of W. inaequalls which co-occur with them beginning from the horizon of sample Dz-66. No intermediate between them has been identified despite a high population variability. The younger populations of Pseudopolygnathus show much lower population variability and have generally a more primitive appearance.This may result from a species distinctness or from character displacement, an influence of the related Weyerognathus lineage.
This is the type species of Pseudopolygnathus andits type population comes from the Bushberg sandstone at Brickeys, Missouri (Branson & Mehl 1934: pl. 24: 24,25), probably significantly younger than the Dzikowiec populations.

Porównanie

Autekologia

Występowanie geograficzne

Zasięg czasowy

Materiały muzealne

Literatura