Rhodesognathus polonicus (Dzik, 1976) from the Mójcza limestone.

Apparatus of Rhodesognathus polonicus (Dzik, 1976).

Diagnoza

The P₂ elements with a bifurcated inner process, P₁ elements with a small, usually denticulated posterior process, M elements with sharp, strongly inclined cusp.

Synonims:

Holodontus superbus, Ligonodina delicata, Ambalodus pulcher, Tetraprioniodus delicatus, Bednarczyk, 1971; Rhodesognathus elegans polonicus Dzik, 1976; partirn Amorphognathus tvaerensis, DZIK 1976; Rhodesognathus elegans polonicus, DZIK 1978.

Porównanie

The species seems to be a successor of the Welsh Rhodesognathus inaequalis, from which it differs mostly in having a smaller and always undivided posterior process of the P₁ elements. The most widespread species of the genus, R. elegans has, as is documented by samples from the Lesieniec borehole, a very similar appearance of the M and other elements of the S series. Their close similarity to cooccurring elements of Amorphognathus is the reason for the late recognition of the apparatus composition in the genus . R. elegans differs from R. polonicus in lacking additional processes in the P₁ and P₂ elements.
The development of the platform in the P₁ elements is extremely variable in the species. This is suggestive of a very weak selection pressure controlling the morphology of the platform elements. Probably this resulted in the evolutionary reduction of the platform in the lineage. Also the morphology of the M elements is variable. Usually they lack an inner- posterior crest but sometimes a rudimentary rib occurs there, which makes it difficult to di stinguish these elements from homologous element of A. tvaerensis.

Autekologia

Występowanie geograficzne

Mójcza, Holy Cross Mountains, Poland.

Zasięg czasowy

In Mójcza the species occurs from 1.8 to 2.4 m above the bentonite (A. tvaerensis/superbus transition zone).

Materiały muzealne

ZPAL

Literatura

Dzik, J. 1994. Conodonts of the Mójcza Limestone. In: J. Dzik, E. Olempska, & A. Pisera. Ordovician carbonate platform of the Holy Cross Mountains. Palaeontologia Polonica 53, 43-128.