J. Paleont., 84(3), 2010, pp. 000–000 Copyright ’ 2010, The Paleontological Society 0022-3360/10/0000-0000$03.00 RUDISTS OF TIBET AND THE TARIM BASIN, CHINA: SIGNIFICANCE TO REQUIENIIDAE PHYLOGENY ROBERT W. SCOTT,1 XIAQIAO WAN,2 JINGENG SHA,3 AND SHI-XUAN WEN3 1Department of Geosciences, University of Tulsa, Tulsa, Oklahoma 74104, ,
[email protected].; 2China University of Geosciences, Beijing, China; and 3LPS, Nanjing Institute of Geology and Paleontology, Chinese Academy of Sciences, Nanjing ABSTRACT—Rudists are a principal biotic component of Cretaceous carbonates in Tibet and in the Western Tarim Basin. Barremian to Maastrichtian carbonate units are widespread on the northern margin of the Indian Plate and in Tethyan tectonic slices that were welded onto Eurasia in successive stages during the Late Cretaceous and Paleogene. In far northwestern Tibet, Barremian-Cenomanian endemic rudists and cosmopolitan orbitolinid foraminifera occupied isolated carbonate platforms in the eastern Tethys. Rudists, corals, and stromatoporoids composed bioherms up to 10 m thick and several kilometers in lateral extent. A unique endemic requieniid rudist, Rutonia, is compared to morphologically similar but older, less derived genera. Associated specimens in this assemblage are indeterminate requieniid valves, monopleurids, and two genera with three radiolitid species that are re-described and taxonomic positions re-evaluated. In southern Tibet, mainly endemic Campanian-Maastrichtian radiolitid rudists and cosmopolitan larger benthic foraminifera contributed to carbonate shelves on the northern Indian Plate near the Cretaceous equator. In the Western Tarim Basin Cenomanian strata yield Tethyan rudist species. Coiling morphometric analysis using the three-dimensional morphology Raup diagram shows that Requieniidae valves in contact with the substrate are convergent with the basic gastropod shell.