Silurian ostracods from the Nyalam region,southern Tibet,China and their implications on palaeoenvironment and palaeobiogeography

The overall occurrence,stratigraphical distribution,palaeoenvironmental and palaeobiogeographical significances of the ostracod faunas from the Silurian Pulu Formation in the Yalai West Ⅱ section,Nyalam region,southern Tibet,China,are documented for the first time.Thirty-two species belonging to 19 genera are identified and figured herein.The ostracod fauna in the Pulu Formation indicates an age of the late Llandovery-Pridoli.The ostracods belong to a podocope-rich association,which suggests an offshore environment for the Yalai West II section.The ostracods of the Pulu Formation have strong affinities with the South China taxa and also share some similarities with those from Baltica.This implies that ostracods could probably benefit from sea-level changes to facilitate faunal exchanges between peri-Gondwana and Baltica.Geographical isolation and global sea-level changes are proposed as the primary factors controlling the palaeobiogeographical distribution of ostracods during the Silurian.