A southward extension of the Silurian Tuvaella brachiopod fauna

The co-occurrence of Tuvaella gigantea Chernyshev, Tannuspirifer pedaschenkoi (Chernyshev), Leptos-trophia elegestica Chernyshev and Stegerhynchus sp. in the Upper Hongliuxia Formation, Barkol, NE Xinjiang, China, shows that this is a representative of the well-known Tuvaella Fauna in China. The correlation of the Tuvaella gigantea Assemblage Zone of the Upper Hongliuxia Formation at its type locality is discussed to document the correlation of this formation with the Pichishui Beds of the Upper upper Chergak Formation in Tuva, the Woduhe Formation m the Lesser Khingan Mountains, and other equivalents based on the presence in some abundance of T. gigantea , and without T. rackovskii. The Tuvaella gigantea-bearing strata are tentatively assigned to the Ludlow. With regard to the paleozoogeographic affinity of the Tuvaella Fauna it is at present suspected by some that the area inhabited by Tuvaella represents a peculiar zoogeographic province or region during the Silurian. However, the information available indicates that the Tuvaella occurrences in east-central Asia represent nothing more than a specialized environmental situation in the light of the presence of a single endemic genus, i.e. Tuvaella itself, among 25 articulate brachiopod genera examined. The evidence of both lithology and brachiopods investigated has important implications for suggesting a shallow, commonly rough-water environment between low intertidal and high subtidal areas.