First records of the genus Ulocrinus miller et gurley (Crinoidea, Cromyocrinidae) from the upper carboniferous beds of the Moscow syneclise and Oka-Tsna Swell

Abstract

Three new species of the genus Ulocrinus, which is recorded for the first time in the Upper Carboniferous of the Moscow Region, are described. These are U. neverovoensis sp. nov. and U. karchevskyi sp. nov. from the Kasimovian Stage and U. grishini sp. nov. from the Gzhelian Stage. Intraspecific variability and structural variations in arms are considered. The uniserial arm structure is established for the first time in juvenile Ulocrinus. The sequence and causes of the acquisition of biserial arms in cromyocrinids are discussed.