Tripodellus gracilis (Branson et Mehl, 1934)
Sugerowana cytacja: Dzik 2015. Tripodellus gracilis (Branson et Mehl, 1934) . Ikonoteka (http://ikonoteka.paleo.pan.pl/xwiki/bin/view/Species/Tripodellus+gracilis+)
 Tripodellus gracilis (Branson & Mehl, 1934) from the D. trigonica and P. jugosus Zones at Kowala and the P. jugosus Zone at Ostrówka in Holy Cross Mountains. 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. 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. |
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