Baby dinosaurs from the Late Cretaceous Lance and Hell Creek formations and a description of a new species of theropod Author Carpenter, Kenneth text Contributions to Geology, University of Wyoming 1982 1982-01-31 20 123 134 journal article 10.5281/zenodo.3238510 a342eb67-842d-41ab-a05d-3f010d0038ec 3238510 Aublysodon mirandus Fig. 7 a , b Material : Teeth: UCM 43447 (UCMP-V5711) H 7 mm , W 2.5 mm ; UCMP 73091 (UCMP-V5622) H 6.3 mm , W 2.2 mm ; UCMP 124367 (UCMP-V75165) H 6.1 mm , W 2 mm ; UCMP 124399 (UCMP-V5620) H 8.9 mm , W 2.6 mm ; UCMP 124406 (UCMP-V73087) H 6.6 mm , W 2 mm ; UCMP 124978 (UCMP-V73087) H 7 mm , W 2.9 mm ; UCMP 124980 (UCMP-V73087) H 6.2 mm , W 2.5 mm ; UCMP 124981 (UCMP-V73087) H 7 mm , W 2.5 mm ; and UCMP 124982 (UCMP-V73087) H 7 mm , W 2.4 mm . W measurements taken transversely across face of tooth near base. Discussion : Leidy (1868) established Aublysodon mirandus on the basis of three incisiform teeth, D-shaped in cross section, which were collected from the Judith River Formation of Montana by Hayden. Subsequent workers, notably Cope (1876) , Lambe (1902) and Osborn (1905) , noted a similarity of two of the serrated teeth with the premaxillary teeth of Deinodon (= Albertosaurus ), and therefore treated Aublysodon as a junior synonym of Deinodon . Lambe (1902) , however, was uncertain of the third tooth, which was unserrated, and placed it tentatively with Ornithomimus altus. Osborn (1905) was less certain of its affinities. Since Leidy’s description, numerous additional specimens of teeth, D-shaped in cross section and lacking serrations, have been collected. Study of these teeth (Carpenter, in preparation ) indicates that Aublysodon mirandus is valid in reference to Leidy’s figured specimen ( Leidy, 1860 , Pl. 9, figs. 41--45 ), here designated as the lectotype . The juvenile specimens, except for one, resemble the lectotype in their D-shaped cross section, parallel sides, and paired posterior lateral ridges that lack serrations. These lateral ridges curve toward one another near the base, but do not meet. This condition is unlike any known tyrannosaur or any theropod premaxillary tooth, in which the serrations diverge from tip to base. One tooth UCM 43447 differs from the lectotype ; it has a slight left-lateral twist of the crown, giving the tooth a spatulate appearance. In all other aspects, however, this tooth is similar to those of Aublysodon .