Taxonomy of the Sandbian (Upper Ordovician) brachiopod Dalmanella kegelensis Alichova, 1953 and the new genus Alichovella

Abstract

The brachiopod species Dalmanella kegelensis Alichova, 1953 is reported in the geological literature of the Baltic region as a species characteristic of the Keila Regional Stage at the Sandbian–Katian transition, and a nominal taxon of a regional biozone. The spatial distribution of D. kegelensis forms a belt around the deeper parts of the palaeobasin. The easternmost occurrences of D. kegelensis have been recorded at the westernmost periphery of the Moscow Basin. The selection of the holotype of the species D. kegelensis from a locality in western Estonia caused some confusion in understanding Alichova’s species, since the description of the species is mainly based on brachiopods collected from northwestern Russia. The earlier attempt to revise the taxonomy of D. kegelensis group brachiopods was unsustainable, while assigning these brachiopods to the genus Horderleyella is no longer feasible. However, two subspecies were identified, which are discussed here as two separate species, kegelensis and oanduensis, belonging to two different genera: one species belongs to the new genus Alichovella in the family Draboviidae, and the second one, following Alichova’s classification, to the genus Dalmanella in the family Dalmanellidae. These species possibly represent somewhat different ages prior to the beginning of the Guttenberg carbon isotope excursion and supposedly differ in their positions on the onshore-offshore transect.

Keywords

• taxonomic revision
• new genus
• guttenberg carbon isotope excursion
• east baltic
• nw russia