Found in 1958 in Guizhou, China by paleontologist Hu Chengzhi. This fossil is distinguished by its broad ulna which makes it unlike other European genera. The broad ulna increased the surface area of the forelimbs, making it more effective in locomotion. Keichousaurus shows many characteristics of its family Pachypleurosauridae such as its short snout and elongated temporal openings. Keichousaurus also had a long serpentine neck with a relatively small head and long tail. The anterior caudal vertebrae possess lateral transverse processes. The morphology of Keichousaurus is most like that of Dactylosaurus, showing long and narrow upper temporal openings that extends to the rear of the skull of which is not found in other pachypleurosaurids. Other differences from pachypleurosaurids include Keichousaurus’ more robust humerus, very broad ulna, and slight hyperphalangy in the manus. The sternum was also lacking in this animal, and the forelimbs were more paddled-shaped, possibly indicating a greater importance of the forelimbs in movement. The pectoral girdle was formed by the paired clavicles, interclavicle, scapulae, and coracoids. Keichousaurus was a primitive quadrupedal tetrapod with limbs laterally placed to the body. Different parts of Keichousaurus grew at different rates, a phenomenon called allometric growth.

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