Paleogeography of the Ordovician bryozoans of the genus Diplotrypa Nicholson (Trepostomida)

Abstract

The stratigraphic and paleogeographic ranges of Ordovician bryozoans of the genus Diplotrypa (Trepostomida: Halloporidae) are analyzed. It is shown that they were then limited in geographic range to the Paleobaltic Basin (the most probable center of origin of the genus Diplotrypa) and to the West Arctic and North American basins. The Silurian bryozoans of this genus were represented by only a few species. In addition, the intercolonial variability of the species Diplotrypa abnormis (Modzalevskaya, 1953) and D. petropolitana (Nicholson, 1879) is studied; Upper Ordovician specimens of these species have been discovered from the Leningrad Region of Russia for the first time. The colonies of these species from the Leningrad Region are compared here with those of Podolia (Western Ukraine) and Vaygach Island (western sector of the Russian Arctic).