Aublysodon mirandus, Leidy, 1868

Carpenter, Kenneth, 1982, Baby dinosaurs from the Late Cretaceous Lance and Hell Creek formations and a description of a new species of theropod, Contributions to Geology, University of Wyoming 20, pp. 123-134 : 130

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 .

Figures

Figures 1-11. Fig. 1, Dromaeosauridae, tooth, UCM 39502. Fig. 2a-h, Sauromithoides inequalis: 20,, buccal view of hatchling left dentary, UCM 41666; c, lingual view; e, dorsal view; b, buccal view of left dentary, NMC 8540 (cast); d, lingual view; f, dorsal view; g, lateral view of hatchling basioccipital, UCM 43218; and h, ventral view. Fig. 3a-c, teeth of Pectinodon bakkeri: a, holotype, UCM 38445; b, paratype, UCM 38446; and c, paratype, UCMP 73098. Fig. 4, Pararıychodon lacustris, tooth, UCMP 124990. Fig. 5a, b, Tyrannosauridae: a as lateral view of UCMP 119853; and b, posterior view. Fig. 6, Theropoda, tooth, UCMP 124987. Fig. 7a, b, tooth of Aublysodon mirandus: a! lateral view of UCMP 124406; and b, posterior view. Fig. 8, Thescelosaurus sp., tooth, UCMP 124973. Fig. 9, Hadrosauridae, tooth, UCM 45060. Fig. 10, Ceratopsidae, tooth, UCM 45057. Fig. 11, Ankylosaurus magniventris, tooth, UCMP 124399. Heavy bars to left of specimens = 2 mm.

Leidy, 1860 , Pl. 9, figs. 41--45