Walliserodus ethingtoni (Fahraeus, 1966) from the Mójcza Limestone.

Apparatus of Walliserodus ethingtoni (Fahraeus, 1966).

Diagnoza

Elements with very deep basal cavities and thin walls . Costate elements (S_0-3, P) with more or less oval cross section at the base, the anteriormost two pairs of elements (M, S₄) with wide base, almost alate.

Porównanie

W. ethingtoni is probably a successor of W. costatus, from which it differs in the elongation of bases in the M and S₄ elements and stronger costation of the remaining elements. The transition has been described quantitatively by Löfgren (1978) in terms of an increasing mean number of keels in the symmetry transition series of S_1-3 and P elements. In Mócza the discontinuity surface cuts across the ranges of these chronospecies making boundaries between them artificially abrupt, but in the Jämtland section the transition seems to be completely smooth. Even in Mójcza specimens from some samples are exactly transitional between Kundan populations of W. costatus and populations of W. ethingtoni. Although the oldest populations attributed by Löfgren (1978) to W. ethingtoni are more or less coeval with the type population of W. costatus, all her specimens show widely gaping basal cavities. This may suggest an allopatrically overlapping ranges of these species. In the course of subsequent evolution, the elements of W. ethingtoni become more prominently ornamented and thinner-walled.

Autekologia

Występowanie geograficzne

Zasięg czasowy

In Mójcza the species ranges from 0.4 m above the discontinuity (E. reclinatus
or E. robustus Subzone) up to 0.5 m above the bentonite (A. tvaerensis Zone). Known occurrences in the Baltic area and Newfoundland range from Aserian (possibly late Kundan)to early Caradoc.

Materiały muzealne

ZPAL

Literatura

Löfgren, A. 1978. Arenigian and Llanvirnian conodonts from Jämtland, northern Sweden. Fossils and Strata 13, 1–129.

Dzik, J. 1994a 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.