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Journal of Zoology: Analysis of forelimb function in basal ceratopsians



http://www.blackwell-synergy.com/doi/abs/10.1111/j.1469-7998.2007.00329.x

Analysis of forelimb function in basal ceratopsians
P. Senter

Here, I present the first study of forelimb function in basal
ceratopsians Dinosauria: Orthischia. I examined forelimb bones and
casts of Psittacosaurus neimongoliensis, Psittacosaurus mongoliensis,
Leptoceratops gracilis and Protoceratops andrewsi. For Ps.
neimongoliensis and L. gracilis, I used manual manipulations of bones
and casts to determine the range of motion at available forelimb
joints. I then used range of motion and morphology to test the
predictions of several hypotheses of forelimb function. Forelimb
morphology and range of motion indicate that Psittacosaurus was an
obligate biped and that Leptoceratops and Protoceratops were capable
of quadrupedal locomotion. Forelimb mobility was too limited in
Psittacosaurus for the hands to reach the mouth. Leptoceratops and
Protoceratops are members of an evolutionary radiation in which an
extension of the glenoid enabled the forelimbs to sprawl laterally for
transverse pivoting, perhaps for display, but quadrupedal locomotion
was accomplished with the elbows tucked in. In Protoceratops, the
radius crosses over the ulna, causing the palms to face caudally. In
Leptoceratops, the radius does not cross over the ulna; the palms face
largely medially and the fingers have been reoriented so that flexion
produces a caudal, propulsive force, even without caudally facing
palms.


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Michael D. Barton
     Bozeman, MT
          MSU Bozeman, History-SETS Major
                 darwinsbulldog@gmail.com
                         Summer 2007: Intern at Heritage and Research
Center, Yellowstone National Park
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