LATE ORDOVICIAN AND EARLY SILURIAN TRIMERELLIDE BRACHIOPODS FROM KAZAKSTAN

All previously known late Ordovician and Silurian trimerellides of Kaz akhstan are reviewed and reillustrated, together with some recently di scovered taxa, including the late Caradoc-Ashgill Palaeotrimerella med ojevi new species from the Chu-lli Range, the late middle Ashgill Gasc onsia cf, worsleyi Hanken and Harper, and Silurian Dinobolus cf. hubei ensis Rong and Yang, both from Central Kazakhstan. Kazakhstanian terra nes appear to contain the oldest;known trimerellide faunas from late L landeilo to early Caradoc. The observed geographic distribution bf Ord ovician trimerellides may be explained as the result of two major migr ations from the Kazakhstanian terranes: 1) during the early Caradoc, t o Gondwana and North America; 2) during the late Caradoc, to Baltica a nd Angaria. All local trimerellide lineages in Kazakhstan became extin ct just before the Hirnantian, and were replaced in the Llandovery by new forms, probably of Chinese origin.