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Bozeman, MT, United States

Woodruff D.C.,Museum of the Rockies | Woodruff D.C.,Montana State University
Journal of Morphology | Year: 2014

Vertebral neural spine bifurcation is considered to be restricted to sauropodomorph dinosaurs, supposedly an adaptation in response to the increasing weight from the horizontally extended cervical column. In this issue of the Journal of Morphology, Cary Woodruff (pp. 1053-106510.1002/jmor.20283) reports about his studies on the soft tissue surrounding neural spine bifurcation in a terrestrial quadruped model species, Ankole-Watusi cattle. With horns weighing up to a combined 90 kg, the Ankole-Watusi is unlike any other breed of cattle in terms of cranial weight and presence of neural spine bifurcation. The cover image shows the world record holding Ankole-Watusi steer "Lurch". The circumference of Lurch's horns are 95.25 cm, and from tip-to-tip the horns are nearly 243 cm in breadth. © 2014 Wiley Periodicals, Inc. Source

Gates T.A.,Utah Museum of Natural History | Horner J.R.,Museum of the Rockies | Hanna R.R.,Terra Paleo Research | Nelson C.R.,Brigham Young University
Journal of Vertebrate Paleontology | Year: 2011

A new hadrosaurid dinosaur, Acristavus gagslarsoni, is here named on the basis of several autapomorphic characteristics of the frontal, postorbital, and dentary. Acristavus is a member of the newly erected clade Brachylophosaurini, which along with its other members, Brachylophosaurus and Maiasaura, constitutes the earliest hadrosaurine hadrosaurid clade. The new taxon occurred approximately 79 million years ago and has been recovered from the Two Medicine Formation of western Montana and nearly simultaneously in the Wahweap Formation of southern Utah. Corresponding with its age and relationship to the other members of the Brachylophosaurini, it is not surprising that Acristavus possesses traits seen in both Brachylophosaurus and Maiasaura, but not necessarily shared between them. One of the most interesting morphological features of Acristavus is the lack of cranial osteological ornamentation, which is in stark contrast to every other hadrosaurid dinosaur except Edmontosaurus. Combining stratigraphic and phylogenetic data from Acristavus yields support for the hypothesis that the hadrosaurid ancestor did not possess cranial ornamentation, and that the subfamilies Hadrosaurinae and Lambeosaurinae each independently developed display structures. © 2011 by the Society of Vertebrate Paleontology. Source

Prieto-Marquez A.,American Museum of Natural History | Bolortsetseg M.,Institute for the Study of Mongolian Dinosaurs | Horner J.R.,Museum of the Rockies
Alcheringa | Year: 2012

We describe a new specimen of small maniraptoran theropod from the Early Cretaceous Öösh locality, Övörkhangai province, central Mongolia. This exemplar ISMD-VP09 preserves a maxillary fragment, two teeth and partial appendicular elements. The strict consensus of a parsimony analysis of 68 coelurosaur taxa places this theropod within Deinonychosauria with an unresolved relationship with the other members of the clade. Support for this clade was based on two unambiguous synapomorphies: maxillary dentition with at least some teeth lacking denticles anteriorly, and ungual and penultimate pedal phalanx II highly modified for hyperextension, with ungual II being more strongly curved and substantially larger than that of digit III. The finding of a new small theropod specimen in the Öösh Formation adds to the deinonychosaur fossil record from the same beds, until now restricted to the dromaeosaurid Shanag ashile. © 2012 Copyright Taylor and Francis Group, LLC. Source

Wings O.,University of Tubingen | Daniela S.-W.,Humboldt University of Berlin | Fowler D.W.,Museum of the Rockies
Neues Jahrbuch fur Geologie und Palaontologie - Abhandlungen | Year: 2011

In April 2006, three new dinosaur localities were discovered in the upper part of the Middle to Late Jurassic Shishugou Formation within "Dinosaur Valley", a classic Junggar Basin locality for Jurassic vertebrates. Recovered bones comprise cervical vertebrae of an adult and a juvenile sauropod and several sauropod forelimb elements. The vertebrae show several affinities to Mamenchisaurus, but a generic assignment cannot be undertaken considering the fragmentary nature of the material and the uncertain status of taxa assigned to the genus Mamenchisaurus. Comparisons make it likely that they are more closely related to Mamenchisaurus and Omeisaurus than to other eusauropods and Euhelopus. All vertebrae expose an accessory lamina at the vertebral centrum, which might also be present but remained undescribed in species of Mamenchisaurus. Indications in the forelimb elements, such as humerus, ulna, and pollex claw, do not allow a determination of the taxa, although there are no distinct differences to Mamenchisaurus. The remains are important because of their extreme size, including potentially the first recognized juvenile remains of a Mamenchisaurus relative, and demonstrate further evidence for the occurrence of non-neosauropod eusauropods in the Junggar Basin. © 2011 E. Schweizerbart'sche Verlagsbuchhandlung Stuttgart Germany. Source

Woodward H.N.,Museum of the Rockies | Woodward H.N.,Oklahoma State University | Freedman Fowler E.A.,Montana State University | Farlow J.O.,Indiana University | Horner J.R.,Montana State University
Paleobiology | Year: 2015

Fossil bone microanalyses reveal the ontogenetic histories of extinct tetrapods, but incomplete fossil records often result in small sample sets lacking statistical strength. In contrast, a histological sample of 50 tibiae of the hadrosaurid dinosaur Maiasaura peeblesorum allows predictions of annual growth and ecological interpretations based on more histologic data than any previous large sample study. Tibia length correlates well (R2>0.9) with diaphyseal circumference, cortical area, and bone wall thickness, thereby allowing longitudinal predictions of annual body size increases based on growth mark circumference measurements. With an avian level apposition rate of 86.4 μm/day, Maiasaura achieved over half of asymptotic tibia diaphyseal circumference within its first year. Mortality rate for the first year was 89.9% but a seven year period of peak performance followed, when survivorship (mean mortality rate=12.7%) was highest. During the third year of life, Maiasaura attained 36% (x=1260 kg) of asymptotic body mass, growth rate was decelerating (18.2 μm/day), cortical vascular orientation changed, and mortality rate briefly increased. These transitions may indicate onset of sexual maturity and corresponding reallocation of resources to reproduction. Skeletal maturity and senescence occurred after 8 years, at which point the mean mortality rate increased to 44.4%. Compared with Alligator, an extant relative, Maiasaura exhibits rapid cortical increase early in ontogeny, while Alligator cortical growth is much lower and protracted throughout ontogeny. Our life history synthesis of Maiasaura utilizes the largest histological sample size for any extinct tetrapod species thus far, demonstrating how large sample microanalyses strengthen paleobiological interpretations. © 2015 The Paleontological Society. All rights reserved. Source

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