page_title: Keichousaurus
section_title: Locomotion
hierarchical_section_title: Keichousaurus / Locomotion
caption_attribution_description: English: Keichousaurus. Scan of fossil bought in Cairns, Australia. Apparently from Guizhou China.
context_page_description: Keichousaurus is a genus of marine reptile in the pachypleurosaur family which went extinct at the close of the Triassic in the Triassic-Jurassic extinction event. The name derives from Kweichow in China where the first fossil specimen was discovered in 1957. They are among the most common sauropterygian fossils recovered and are often found as nearly complete, articulated skeletons, making them popular among collectors. Keichousaurus, and the pachypleurosaur family broadly, are sometimes classified within Nothosauroidea, but are otherwise listed as a separate, more primitive lineage within Sauropterygia.
context_section_description: The locomotion of Keichousaurus probably resembled (in part) the "underwater flight" that plesiosaurs employed. The flattened forelimbs would likely have acted as hydrofoils. The hindlimbs show less specialization, and may therefore have acted as stabilizers and control surfaces, such as is seen in extant sea turtles. The intermediate nature of the limb morphology implies that there was also, to some extent, the kind of 'crawling through the water' seen in small freshwater turtles. The powerfully built pectoral girdle allowed for the attachment of strong muscles, but their location beneath the shoulder favours the underwater flight model. Despite the specialization of the limbs, the tail also shows adaptations to an aquatic existence. Lateral transverse processes of the anterior caudal vertebrae show that powerful muscles enabled the tail to beat or at least undulate from side to side. This would imply some distal lateral compression, but this is not recorded in soft-tissue preservation. The long neck was primarily concerned with prey-capture. The combination of powerful limbs and tail would have made K. hui an adept and maneuverable predator.
caption: 20cm fossil Keichousaurus
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