Kritosaurus cf. Kritosaurus breviceps (Marsh, 1889a)

Figure 8U, V

Hadrosaurus breviceps MARSH, 1889a, p. 335.

Trachodon breviceps: MARSH, 1896a, p. 224.

? Kritosaurus breviceps: LULL AND WRIGHT, 1942, p. 170.

About a dozen teeth of a large flat-headed (hadrosaurine) ornithopod are present in the collections. AMNH 8525 consists of a crown (30 mm. long) making an obtuse angle of about 120 degrees with the fang (fig. 8U, V). The teeth are similar in size and morphology to each other and appear to belong to a single species. The crown is diamond-shaped with a bluntly rounded apex. A distinct medial keel is present above the slightly concave lateral edges. No ornamentation is found on the sides or keel. These teeth are probably referable to Kritosaurus, the only flat-headed ornithopod to be reported from the Judith River Formation (Lull and Wright, 1942, p. 171). The species was originally described by Marsh (1889a, p. 335) as Hadrosaurus breviceps, and later (Marsh, 1896a, p. 224) as Trachodon breviceps. The systematic position of Hadrosaurus and Trachodon has been discussed at length by Sternberg (1936). Trachodon mirabilis seems to be more closely related to the crested lambeosaurines rather than to the flat-headed hadrosaurines. Sternberg (1936) has suggested that use of Trachodon mirabilis be abandoned.

Lull and Wright (1942, p. 171) described and figured the dental battery of K. breviceps obtained from the Judith River Formation. The teeth recently collected probably belong to the same species. Comparison of K. breviceps with other species of Kritosaurus from the Oldman Formation is of little use as the Judith River material is still not sufficiently well known.