Amorphognathus ordovicicus Branson & Mehl, 1933 from the Mójcza Limestone.

Apparatus of Amorphognathus ordovicicus Branson & Mehl, 1933.

Diagnoza

The M elements with a long cusp dominating over the denticles, which occur in very low numbers, usually a single one on each process.

Porównanie

Some of the P₁ elements from the uppermost part (Zalesie Formation) of the Mójcza section have an unbranched anterior proces associated with a very wide platform. This seems to be characteristic of the species although there are several other associated specimens which differ from the older ones of A. superbus only in a slightly less developed inner lobe of the posterior process and a shorter, slightly more twisted inner process. The difference is not great and is much obscured by the population variability. All the associated M elements from the marly part of the section have the cusp strongly dominating over a few associated denticles, which is the diagnostic feature of the species . Still some doubts remain whether this is enough to consider these Mójcza populations conspecific with the British ones and the zonal boundaries based on the evolution of Amorphognathus must remain tentative. The main reason for this uncertainty is the very limited evidence on the population and ontogenetic variability of the M elements.

Autekologia

Występowanie geograficzne

Almost cosmopolitan.

Zasięg czasowy

Populations from the marly limestones of the Zalesie Formation in Mójcza are
assigned to the species with some hesitation. Undoubtedly conspecific with British ones are the populations from the Zalesie Formation in Zalesie and in Miedzygorz (in the latter locality well preserved M elements were found).

Materiały muzealne

ZPAL

Literatura

Bergström, S.M. & Leslie S.A. 2010. The Ordovician zone index conodont Amorphognathus ordovicicus Branson & Mehl, 1933 from its type locality and the evolution of the genus Amorphognathus Branson & Mehl, 1933. Journal of Micropalaeontology 29, 73−80.

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.