. Bulletin. Natural history. 136 PEABODY MUSEUM BULLETIN 23 Referred Specimen. KU no. *1024, from the Niobrara Chalk, collected by Charles H. Sternberg. Diagnosis. Narial emargination begins dorsal to fourth maxillary tooth. Fourteen teeth in maxilla. Splenial has weak median dorsal keel on articulating surface. Fourteen teeth in dentary. Dentary relatively heavy with parallel dorsal and ventral margins up to point beneath third and fourth dentary tooth, margins tlien converge rapidly ante- riorly to a rounded tip. Marginal teeth short relative to other species of Mosasaurus and triangular in
. Bulletin. Natural history. 136 PEABODY MUSEUM BULLETIN 23 Referred Specimen. KU no. *1024, from the Niobrara Chalk, collected by Charles H. Sternberg. Diagnosis. Narial emargination begins dorsal to fourth maxillary tooth. Fourteen teeth in maxilla. Splenial has weak median dorsal keel on articulating surface. Fourteen teeth in dentary. Dentary relatively heavy with parallel dorsal and ventral margins up to point beneath third and fourth dentary tooth, margins tlien converge rapidly ante- riorly to a rounded tip. Marginal teeth short relative to other species of Mosasaurus and triangular in lateral outline, prisms numerous (6-7) on external face, as many as eleven distinct prisms on internal face. Discussion. The refeiTed specimen includes the right side of a muzzle, with the pre- maxilla, dentary, splenial, jugal and possibly also a pterygoid and ectopterygoid, al- though the latter two elements may belong to a Tylosauriis. The atlas and axis Text-fig. 79. Muzzle referred to Mosasaurus ivoensis (KU 1024, x %). and a large part of the left forepaddle are also present. The maxillary teeth are indistin- guishable from those described by Persson (1959, p. 462) from the lower Campanian of souUiern Sweden, and later named M. hoffmanni ivoensis by the same author (Pers- son, 1963, p. 5). The relationship of the above specimen with Mosasaurus is shown by the abbreviated rostrum of the premaxilla and the number (14 each in the dentary and maxilla) and form of the teeth. The articular surface of the splenial is more nearly circular when viewed from the posterior than tliat of any other mosasaur known to die author. The jugal resembles that of Mosasaurus except that the ventroposterior process is very weakly developed. A zygantrum is apparently absent on the axis vertebra (Williston, 1902, p. 249). The foreflipper of this specimen was figured by Williston (1902, pi. 12 lower figure). The humerus bears evidence of its Mosasaurus affinities by its general proporti
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