Abstract
This research resulted from the determination that MCZ 8791 is a specimen of Deinonychus antirrhopus between one and two years of age and that the morphological variations within particular growth stages of this taxon have yet to be described. The primary goal of the research is to identify ontogenetic variations in this taxon. Histological analyses determined that the Deinonychus specimens AMNH 3015 and MOR 1178 were adults. Comparisons are made between MCZ 8791 and these adult specimens. The holotype, YPM 5205, and the other associated specimens of this taxon within the YPM collection are similar in size and morphology to AMNH 3015. Further comparisons were made with the three partial specimens OMNH 50268, MCZ 4371, and MOR 1182. Although these specimens represent only a partial ontogenetic series, a number of morphological variations can be described. One secondary goal of this research is to compare the known pattern of variable, informative, ontogenetic characters in MCZ 8791 to a similar pattern of morphological characters in the sub-adult dromaeosaurid specimen Bambiraptor feinbergorum, AMNH FR: 30556. If the characters that have been determined to represent variable juvenile morphology in the ontogeny of Deinonychus are exhibited in Bambiraptor, this study will begin the process of determining whether a similar, conservative, ontogenetic pattern exists throughout the rest of Dromaeosauridae. If defensible, it may reduce the number of sympatric taxa within this clade. The other secondary goal relates to the forelimb function. The approximate body size, forelimb length, wrist development, and the presence of a more prominent olecranon on the ulna of MCZ 8791 support the hypothesis that juveniles of this taxon possessed some form of flight capability.
Highlights
IntroductionThe dromaeosaurid Deinonychus antirrhopus [1] is known from several specimens collected from the Early Cretaceous Cloverly Formation of Montana [1,2,3] and one specimen from the Antlers Formation of Oklahoma, Oklahoma Museum of Natural History (OMNH) 50268 [4]
The dromaeosaurid Deinonychus antirrhopus [1] is known from several specimens collected from the Early Cretaceous Cloverly Formation of Montana [1,2,3] and one specimen from the Antlers Formation of Oklahoma, Oklahoma Museum of Natural History (OMNH) 50268 [4].PLOS ONE | DOI:10.1371/journal.pone.0121476 April 15, 2015Ontogenetic Variation in Deinonychus antirrhopusThe growth stages of the four Yale/Peabody Museum of Natural History (YPM) specimens were not determined in Ostrom’s original description
Characters possessed by the juvenile specimens Museum of Comparative Zoology (MCZ) 8791 and/or OMNH 50268 that variably transform or disappear by the adult stage within the ontogeny of this taxon are defined as variable ontogenetic characters
Summary
The dromaeosaurid Deinonychus antirrhopus [1] is known from several specimens collected from the Early Cretaceous Cloverly Formation of Montana [1,2,3] and one specimen from the Antlers Formation of Oklahoma, Oklahoma Museum of Natural History (OMNH) 50268 [4]. The growth stages of the four Yale/Peabody Museum of Natural History (YPM) specimens were not determined in Ostrom’s original description. In 1982, a partial skeleton of a small theropod, Museum of Comparative Zoology (MCZ) 8791, was recovered from an Early Cretaceous, Cloverly Formation site in central Montana. It was collected by Charles Schaff from the Museum of Comparative Zoology at Harvard University. Two incomplete coracoids and the right manual II-2 phalanx from MCZ 8791 have been prepared and identified
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