A taxonomic revision of the Early Devonian dalmanitid trilobite Kasachstania Maksimova, 1972 from central Kazakhstan

Abstract

The dalmanitid trilobite Kasachstania Maksimova, 1972, previously reported from the Lower Devonian of Kazakhstan and North America (USA) and the upper Silurian–Lower Devonian of South America (Bolivia and Argentina), is revised. Kasachstania kasachstanica (Balashova in Maksimova,1968) and K. septicostata (Maksimova, 1968) are regarded as junior synonyms of the type species K. saryarkensis (Maksimova, 1960), all from the Lower Devonian of the type locality in central Kazakhstan (northern Balkhash). On the basis of a new diagnosis, K. ulrichi ulrichi (Delo, 1940) from the Emsian of the United States, K. ulrichi asiatica (Maksimova, 1968), K. pristina (Maksimova, 1968), and K. alperovichi Pour et al., 2019, from the Lower Devonian of Kazakhstan, K. andii (Kozłowski, 1923) from the upper Silurian–Lower Devonian of Bolivia, and K. gerardoi Edgecombe and Ramsköld, 1994, from the upper Silurian–Lower Devonian of Bolivia and Argentina are excluded from Kasachstania. This genus, represented only by K. saryarkensis and K. kiikbaica (Maksimova, 1968), is restricted to the Lower Devonian of central Kazakhstan, corresponding to the Balkhash–Mongolo–Okhotsk province in the paleobiogeographic context of the Old World Realm, instead of being nearly cosmopolitan as previously considered. In addition, we provide some remarks about Saryarkella Maksimova, 1978b, a monospecific dalmanitid genus largely overlooked although valid from the Emsian of the same area in central Kazakhstan.