Acta Palaeontologica Polonica

Early Ordovician conodonts from the Barrandian and Bohemian-Baltic faunal relationships

Jerzy Dzik

Acta Palaeontologica Polonica 28 (3-4), 1983: 327-368

The typical Baltic conodont Baltoniodus has been identified in the Bohemian Early Ordovician Klabavian and Sarkan stages. In the upper part of the Klabava Formation (locality Svatostepansky rybnik near Myto) Baltoniodus is associated with species of the genera Drepanoistodus, Scalpellodus and Drepanodus, which also occur in the Baltic area. This contrasts with dissimilarity, stressed by many autnors between Baltic and Bohemian faunas thought to belong to different paleozoogeographic provinces. A review of other groups of fossils indicates that migrations between these regions in the Early Ordovician were not uncommon. Klabavian B. bohemicus sp. n. is morphologically intermediate between Acodus deltatus, B. crassulus, and B. triangularis sensu Lindstrom, 1971 and may be identical with the oldest populations of B. navis sensu Van Wamel, 1974. According to the interpretation presented of the evolutionary relationships of B. bohemicus sp. n., the upper part of the Klabava Formation is correlated with the Latorpian-Volkhovian boundary. The conodontophorid assemblage from Myto differs in its much lower diversity from Baltic assemblages containing species of the same genera. This supports the concept of the cold-water nature of the Bohemian Ordovician. It is suggested that the subpolar ("Antarctic") convergence was between Baltica and the Moldanubicum, and selectively separated faunas in the Early Ordovician.

Key words: conodonts, biogeography , Baltic region, Bohemia, Ordovician, evolution, biostratigraphy.

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