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Vagacertops (ceratopsian) postcranial skeleton (free pdf)



Ben Creisler
bcreisler@gmail.com

A new online ejournal in open access:

Robert B Holmes (2014)
The postcranial skeleton of Vagaceratops irvinensis (Dinosauria, Ceratopsidae).
Vertebrate Anatomy Morphology Palaeontology 1:  1-21
ISSN 2292-1389
http://ejournals.library.ualberta.ca/index.php/VAMP/article/view/21605
http://ejournals.library.ualberta.ca/index.php/VAMP/article/view/21605/17221




The postcranial skeleton of Vagaceratops (= Chasmosaurus) irvinensis
(CMN 41357), lacking only the tail, most of the left front and left
hind limbs, and portions of the pelvis, is preserved in articulation.
It is one of the most complete, best articulated ceratopsid skeletons
known. Both the manus and vertebral column exhibit conspicuous
pathologies, possibly an indication of advanced age at the time of
death. The vertebral column comprises a syncervical, six additional
cervical vertebrae, and 12 dorsals. A partial synsacrum is represented
by two dorsosacrals, four sacrals, two caudosacrals, and a partial
third caudosacral centrum. The ribcage, although crushed, is nearly
complete. The sternum is unusually wide compared with other
ceratopsids. As in other chasmosaurines, the humerus bears a prominent
deltopectoral crest that forms the anterior edge of the broad,
rectangular proximal humeral expansion. The medial tuberosity is
separated from the dorsal surface of the humerus by a distinct notch.
The insertion for the latissimus dorsi is conspicuous. The
deltopectoral crest extends a full half of the distance to the distal
end of the humerus. Epipodials of the forelimb are relatively short
compared to the corresponding propodial. The ulna has a long,
distinctly triangular olecranon, broadly rounded anterolateral
process, prominent medial process, and a deeply concave trochlear
notch. The terminal phalanges on the fourth and fifth manual digits
are relatively large, and unlike other ceratopsids have distinct
distal ?articular facets. The fourth trochanter of the femur is
relatively proximal in position. This study and other recent studies
of ceratopsid postcrania suggest that potentially useful taxonomic
variation is present in the number of dorsosacrals, size of the groove
on the ventral surface of the sacrum, morphology of the last dorsal
and dorsosacral ribs, morphology of the scapula and proximal expansion
of the humerus, morphology of the ulna, ratio of humerus/epipodium,
morphology of the fifth manual digit, and position of the fourth
trochanter of the femur.