NEW MATERIAL OF IKECHOSAURUS-SUNAILINAE (REPTILIA, CHORISTODIRA) FROMTHE EARLY CRETACEOUS LAOHONGDONG FORMATION, ORDOS BASIN, INNER-MONGOLIA, AND THE INTERRELATIONSHIPS OF THE GENUS

New material of Ikechosaurus sunailinae from the Early Cretaceous Laoh ongdong Formation of the Ordos Basin, Inner Mongolia, People's Republi c of China, is described. This material, which includes well-preserved articulated skeletons and a series of isolated elements, demonstrates that Ikechosaurus is more closely related to Champsosaurus than to Si moedosaurus, sharing with Champsosaurus the presence of an elongate sn out, anteriorly constricted parasphenoid with the foramen canalis caro ticus internus located in or near the suture between the parasphenoid and the pterygoid, an anterior extension of the anterior end of the ju gal, and an elongate symphysis including the splenial. Ikechosaurus is primitive relative to Champsosaurus in the anterior position of the i nternal narial openings, in the less strongly flared temporal region w ith the temporal openings placed largely above one another, in the abs ence of fenestra in the occiput between the parietal and squamosal, an d in the interpterygoid vacuity bordered posteriorly by the basispheno id. Ikechosaurus and Tchoiria are at a similar grade of evolution, but can be separated by details in the arrangement of bone forming the sk ull roof.