Conodont association of the Bashkirian-Moscovian boundary interval of the Donets Basin, Ukraine

Ten sections spanning the Bashkirian-Moscovian boundary interval were studied in the Donets Basin. Six of them contain most representative conodont and foraminifer associations. In this paper we focused on three the most complete sections that include stratigraphically important conodont species, which belong to the Declinognathodus, Idiognathoides, Idiognathodus, Neognathodus, “Streptognathodus”, Mesogondolella and Diplognathodus genera. The majority of those species are widely distributed, which makes the correlation to other areas reliable. Two biotic events in conodont evolution were discovered in these sections. Two conodont lineages established here are considered as potential markers for the definition of the lower boundary of the Global Moscovian Stage: D. marginodosus – D. donetzianus and Id. sulcatus sulcatus – Id. postsulcatus. The conodonts D. donetzianus and Id. postsulcatus, both proposed before as potential markers for the de? nition of the GSSP at the Bashkirian-Moscovian boundary, are described and compared to those from the other areas. The entry of D. donetzianus is updated and con? rmed to the top of the limestone K1 in both sections, the Zolota Valley and the Malo-Mykolaivka sections. The other proposals for the de???? nition of the lower Moscovian boundary by conodonts are discussed. Three conodont zones characterize the Bashkirian-Moscovian boundary interval. These are, in ascending order: the Id. tuberculatus – Id. fossatus Zone and D. marginodosus Zone from the upper Bashkirian, and D. donetzianus Zone from the lower Moscovian. They were recently described and shortly given in this paper.

Morphometric patterns in Middle Triassic Neogondolella mombergensis (Conodonta), Fossil Hill, Nevada

The Fossil Hill Member of the Prida Formation (Fossil Hill, Nevada) yields one of the most continuous records of Middle Triassic conodont evolution currently known. Because of different taxonomic viewpoints, this record has been alternately interpreted to represent either morphological stasis or gradual, biostratigraphically significant morphogenesis. Univariate and multivariate morphometric analysis of 18 successive Neogondolella Pa element populations suggests that the majority of specimens at Fossil Hill (including N. constricta emend. sensu Nicora and Kovacs, 1984) belong to a single, morphologically diverse species, Neogondolella mombergensis (Tatge). Time series of individual character means from 18 stratigraphic horizons in the Fossil Hill display nondirectional morphologic trends for which a random walk model cannot be rejected. Time series of transformed multivariate means constitute biologs that may prove useful in regional correlation.