Great Basin Naturalist


The new sauropod, Cathetosaurus lewisi, is named and assigned to the Camarasauridae; it was collected from the Upper Jurassic Morrison Formation in western Colorado in 1967. Novel structural features of the skeleton in this genus, particularly in the axial skeleton, enabled it to assume and function to an unknown degree in a bipedal posture. Comparisons are made between C. lewisi and previously described sauropods. The following problems of sauropod locomotion are discussed; (1) sauropods lack two elements, sesamoids and patella, present in titanotheres; (2) sauropod limb and foot musculature, lacking leverage, is very inferior to that of titanotheres; (3) no previously described sauropod displays adequate structural specializations for voluntary bipedalism comparable to that of the new genus Cathetosaurus; (4) great weight and cartilaginous limb and foot joint structure restricted sauropods to a slow tempo of locomotion, suggesting a moderate to low rate of catabolic metabolism. Mammal and sauropod foot bones and their function are compared, and comparisons are made between the weight and structure of modern mobile machines and the locomotion and movement of large sauropods. Occurrence and taphonomy of C. lewisi are discussed.