A new data about systematic composition of Thanetian flat terebratulids of South-West Crimea
The revision of flat Thanetian terebratulids of South-West Crimea, included until the last time Terebratula bisinuata Lam., T. mischensis Ilyina, T. plana Zel. and Oleneothyris pinguinensis Zel., has been made. The material of studying has been the collection of brachiopods, collected from the lower and middle parts of Kachinsky suite and comprising 403 specimens. The investigation has shown that at the all age stages brachiopods are characterized by significant individual variability of shell outline, increased with age. Beginning with length of 5.3 sm. all terebratulids have folds. The main significant morphological features of terebratulids are also much variable. The given data allows defining the species Terebratula mischensi and Terebratula plana as junior synonyms of Terebratula bisinuata. Theconclusionsjustifiedtheruleof incompatibility of two or more closely relatedspecies in the single ecological niche. The illustrations of 26 studied samples are shown.