DROMAEOSAURIDAE

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 : 127

Family DROMAEOSAURIDAE

Fig. 1

Material: Dentary fragments: UW 13684 (UCMP- V 5003); and UCMP 125238 (UCMP-V73089). Teeth: UCM 39502 (UCMP-V5711) H 1.7 mm, W 2 mm; UCM 45055 (UCMP-V5620) H 2.6 mm, W 2.2 mm; UCMP 124983 (UCMP-V73087) H 2.1 mm, W 2 mm; UCMP 124984 (UCMP-V73087) H 3 mm, W 2.1 mm; and UCMP 124985 (UCMP-V73087) H 2.7 mm, W 2.1 mm.

Discussion: The two dentary fragments are much alike and are probably conspecific. UW 13684 is the more complete, measuring 15 mm long and containing the base of two teeth separated by an empty alveolus. UCMP 125238 is 6.5 mm long and contains a nearly complete tooth and a partial alveolus. In both fragments, the alveoli are longer than wide and subrectangular in shape. No interdental plates are present. The inner and outer dental parapets are nearly equal in height. On the external surface the dental foramina are anteroposteriorly elongated and terminate at faint grooves which extend ventrally from the dental border. The preserved parts of the teeth are strongly compressed laterally, and have a shallow sulcus on both sides of the root; this sulcus does not extend onto the crown. The tip of the crown is missing in UCMP 125238 ; however, the tooth is complete enough to show that it was posteriorly recurved, with well developed serrations on the posterior edge and faint, poorly developed ones on the anterior edge. There are 11 serrations per 2 mm on the posterior edge; those on the anterior edge cannot be counted. Reconstructed, the crown was about as long anteroposteriorly as high.

These dentary fragments are similar to Velociraptor in the absence of interdental plates, the subequal height of the inner and outer dental parapets, the long and narrow, subrectangular aveoli, and in the elongated external foramina (see Sues, 1977, P1. 16). Although these dentary fragments may be those of Velociraptor , they are too fragmentary for positive identification. As will be shown elsewhere (Carpenter and Paul, in preparation), Velociraptor occurs in North America and may differ enough from Dromaeosaurus to warrant its own family.

Isolated teeth used in this study are almost as long anteroposteriorly as they are high, strongly compressed laterally, and recurved with serrations well developed along the posterior margin. Development of anterior serrations vary in strength. In these features, these teeth resemble the posterior teeth of Velociraptor mongoliensis (e. g., AMNH 6515 ). Many of the teeth in the collections show some degree of usage wear, especially at the tip.

Figures

Figures