Diagnoza

Wide and strongly asymmetric basal cone (pit) of P₁ element, its tip bent posteriorly, rounded lobe near the cusp even in large specimens.

Porównanie

No specimens of the morphology proposed to be typical for Tripodellus expansus (Sandberg et Ziegler, 1979) are known from the Holy Cross Mountains but some mature elements with an extremely wide platform approach that morphology (e.g., in sample Ost-5). They share with those from Montana their asymmetric larval basal cavity, which places them in the T. gonioclymeniae lineage, but they do not show so strong a widening of the platform and in occlusal view do not differ form T. gracilis. In sample Ost-7 the dominant elements with asymmetric larval basal cavity are associated with rare specimens having a wider platform, which do not show a separation of the basal cavity at all, thus being similar in those respects to older populations of T. gracilis. In fact, such asymmetry and incipient separation of the basal cone is observable in the population of T. gracilis from sample Ost-12, but the basal cone is small and well visible only in juvenile and strongly asymmetric specimens. It seems thus that this stage in the evolution of the Tripodellus branch is marked by expansion of juvenile characters to later ontogenetic stages. Palmatolepis deflectens sigmoidalis of Ziegler (1962) seems to be based on a juvenile T. gracilis.

Possibly, ‘Palmatolepis expansa’ is a morphotype within the range of population variability of T. gracilis. Perri and Spaletta (1991) classified within ‘P. expansa’ specimens that do not show asymmetry of the basal cavity. This indicates how misleading may be the concept of that species and that stratigraphic decisions based on it are of questionable value.

Autekologia

Występowanie geograficzne

Jabłonna, Ostrówka, Miedzianka, Kowala, Gołogłowy, and Dzikowiec.

Zasięg czasowy

L. styriacus to D. trigonica Zones. 

Materiały muzealne

ZPAL: 11,928 specimens.

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.