Glyptorthis(Foerste, 1914) andBassettellanew genus (Brachiopoda: Orthida) from the Late Ordovician of the east Baltic

Abstract

The GenusGlyptorthisFoerste, 1914 is a rare component of the Late Ordovician to early Silurian brachiopod faunas of the East Baltic. Hints and Röömusoks (1997) reported on the occurrence ofGlyptorthisin seven stratigraphie levels within the Upper Caradoc, Ashgill and Llandovery, in a paper summarizing the stratigraphy of Estonia. To date, however, very few of these brachiopods have been studied in detail. Three species from the Ashgill and Llandovery were established by Rubel (1962) and Röömusoks (1970), whereas some unnamed Caradoc taxa were listed only in the latter paper. Collections made since 1987 by S. S. Terentiev and M. A. Zuykov revealed that rare specimens ofGlyptorthis-like brachiopods occur in fossiliferous lower Caradocian (Idavere Regional Stage) strata in the western part of the St. Petersburg region, northwestern Russia. These specimens, assigned herein to a new glyptorthid genus and species Bassettella gracilis, comprise the core of this paper. Moreover, generic affinities of Estonian species from the Ashgill currently assigned toGlyptorthisare discussed. The type specimen of J. Hall (1847) in the American Museum of Natural History (New York) and specimens from the type area in the Sch¨chtert Brachiopod Collection in the Peabody Museum of Natural History, Yale University (New Haven), have been investigated for comparative purposes.