Ikechosaurus

Abstract: New material of Ikechosaurus sunailinae from the Early Cretaceous Laohongdong Formation of the Ordos Basin, Inner Mongolia, People's Republic 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 Simoedosaurus, sharing with Champsosaurus the presence of an elongate snout, anteriorly constricted parasphenoid with the foramen canalis caroticus internus located in or near the suture between the parasphenoid and the pterygoid, an anterior extension of the anterior end of the jugal, and an elongate symphysis including the splenial. Ikechosaurus is primitive relative to Champsosaurus in the anterior position of the internal narial openings, in the less strongly flared temporal region with the temporal openings placed largely above one another, in the absence of fenestra in the occiput between the parietal and squamosal, and in the interpterygoid vacuity bordered...

Abstract: Ikechosaurus gaoi nov.sp. is based on a fragmentary skeleton from the Jiufutang Formation (Early Cretaceous) of Chifeng City, Inner Mongolia (P.R. China). Its skull differs from that of L sunailinae, from the Laohongdong (Luohandong) Formation of the Ordos Basin, in having larger teeth and sparser tooth arrangement under the orbits; the lower jaw has a triangular shape in cross-section, with a sharp ventral surface: the neck region between the dorsal plate and basal part of the ilium is more contracted; the shaft of femur is more twisted and the boundary between the internal trochanter and the femoral head is clearer. Features of the postcranial skeleton indicate that this animal was perhaps a small, swift runner. Like Simoedosaurus, it was probably only semi-aquatic.