Diagnoza

This is another species of the genus with very variable and difficult to determine sp elements and other elements of the apparatus probably similar to other species of Pinncognathrzs( Fig. 20J, K). Being best represented in the sample Dz-28 it may represent a stage, or just an oscillation, in the evolution of the Pinacognathus lineage. Generally, the platform of sp elements is wide, flat and relatively thin, with a strong occlusal omamentation of the ribs. The margin in some elements is crenulated but in others remains smooth. There is a remarkable variability in element shapes, some being close to juveniles of Dinodus lobatus. Most of the sp elements athibuted to this species are strongly angular and bent at the cusp so their basal surface is concave. Some juvenile specimens from sample Dz-l4have their platform linear in profile and may represent yet another related or convergent$ similar species. The well separated, typically polygnathid pit (Fig. 20J) may, however, gape also in the more dorsal part of the element, which may make distinction from the associated Pinacognathus sp. problematical. In fact, the apparatuses of these two species may appear identical (Figs 15D, E, 24). Unfortunately, as in the case of P inornatus, no Dzikowiec sample contains elements of this species in larger number without being associated with P sp. This makes separationo f their apparatusesp ractically impossible. Most probably they are closely similar.

The type populations of Polygnathus fornicatus Ji, Xiong, & Wu, 1985 co-occurs with S. carinthiaca at Muhua. Its relationship to P. flabellum Branson & Mehl, 1938 remains to be clarified - specimens identified by Voges (1959) as similar to this North American species are apparently conspecific with those from Dzikowiec. The Polish populations attributed here to P fornicatus may appear conspecific with Siphonodella uralicaZhuravlev, 1994, which may be based on juveniles of D. lobatus, as suggested by small size of the sp elements figured by Zhwavlev (1994).

Porównanie

Autekologia

Występowanie geograficzne

Zasięg czasowy

Materiały muzealne

Literatura