Mutrellataxis asymmetrica sp.n. from the L styriacus Zone at Ostrowka (sample Ost-12) specimens ZPAL cXVI/ 1575, 1567, 1576, 1573 (holotype D)

Diagnoza

Sharp conical cusp with lenticular section, smooth surface and sharp edges.

Porównanie

From typical species of Mitrellataxis, the new species differs in a smooth surface of the cusp, from M. circularis in sharp-edged cusp and generally narrow base. The idea that the Famennian ‘simple cones’ are isolated denticles of secondarily simplified icriodontids fits especially this species. The elements show linearly extending bases, quite long in some specimens, and they may be easily visualised as being distributed along a non-minerized process.

Elements of M.? asymmetrica resemble most the coniform elements of Icriodus (e.g., that on Fig. 10U) differring only in that no incipient denticles or angulations develop near the bese, as is usual in at least some elements of Icriodus. This is thus either a case of homeomorphy or the species is the end-member of an icriodontid lineage with reduced P₁ elements. Wang (1989) illustrated a similar element from the Polygnathus perbonus Zone of the Emsian under the name Drepanodina subcircularis Wang, 1981. This may mean that the lineage was long-lasting.

Autekologia

Występowanie geograficzne

Sparsely occurring in many samples ranging from the P. trachytera Zone at Kowala and Jabłonna to the L. styriacus Zone at Ściegnia and Ostrówka.

Zasięg czasowy

Materiały muzealne

52 specimens ZPAL

Literatura

Dzik, J. 2006. The Famennian "Golden Age" of conodonts and ammonoids in the Polish part of the Variscan sea. Palaeontologia Polonica 63, 1-359.