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A NEW SPECIES OF CAMPTOSAURUS (ORNITHOPODA: DINOSAURIA) FROM THE MORRISON FORMATION (UPPER JURASSIC) OF DINOSAUR NATIONAL MONUMENT, UTAH
A new species, Camptosaurus aphanoecetes, is named for a partial skeleton of ornithopod dinosaur from the Morrison Formation (Upper Jurassic) of Dinosaur National Monument, Utah. The specimen was originally described as Camptosaurus medius Marsh, 1894, and later referred to Camptosaurus dispar (Marsh, 1879). Comparison of the specimen with a large sample of C. dispar from Quarry 13 shows differences in the proportions and shape of various axial and appendicular elements. Based on the dorsoventrally depressed form of the ilium, Camptosaurus depressus Gilmore, 1909 (Lower Cretaceous of South Dakota) is assigned to the Barremian genus Planicoxa DiCroce and Carpenter, 2001, as Planicoxa depressa, new combination. The well-preserved, undistorted forelimb material of C. aphanoecetes allows for a biomechanical analysis. The range of motion is rather limited throughout the forelimb. The analysis supports the quadrupedal locomotion previously hypothesized for Camptosaurus Marsh, 1885, from limb ratios, fusion of the wrist, and presence of short digits.
34.—Skeletal reconstructions of Camptosaurus. A, C. aphanoecetes; B, C. dispar (adult); C, C. dispar (juvenile based on USNM 2210, holotype C. nanus).