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Bonitasaura (Titanosauria) postcranial anatomy



Ben Creisler
bcreisler@gmail.com

A new online paper:

Pablo A. Gallina & Sebastián Apesteguía (2015)
Postcranial anatomy of Bonitasaura salgadoi (Sauropoda, Titanosauria)
from the Late Cretaceous of Patagonia.
Journal of Vertebrate Paleontology (advance online publication)
DOI:10.1080/02724634.2014.924957
http://www.tandfonline.com/doi/full/10.1080/02724634.2014.924957#

Bonitasaura salgadoi, from the Bajo de la Carpa Formation (Santonian),
Río Negro, Argentina, is a well-preserved titanosaur. Previously
described cranial material of Bonitasaura demonstrated the presence of
square jaws in titanosaurs, but the nearly complete postcranium of the
holotype specimen remains mostly undescribed. We present an
osteological description of this material, which includes cervical,
dorsal, and caudal vertebrae, elements of the pectoral and pelvic
girdles, as well as forelimbs and hind limbs. Characteristics of the
axial skeleton suggest that the holotype represents an immature
individual. The base of the neck was likely robust, based on the
broad, rhomboidal neural spines in the vertebrae across the
cervicodorsal transition. Bonitasaura is assigned to Titanosauria
based on lateral constriction of the neural canal in the anterior
cervical vertebrae, presence of anterior and posterior
spinodiapophyseal laminae in the middle to posterior dorsal vertebrae,
distolateral expansions of the middle dorsal vertebral neural spines,
absence of hyposphene-hypantrum articulations in posterior dorsal
vertebrae, anterior and middle caudal vertebrae with strongly
procoelous centra, anterior caudal vertebrae with transverse processes
extending beyond the posterior margin of the centrum, and other axial
features. The appendicular anatomy of Bonitasaura also supports
referral to Titanosauria based on characters such as the semilunar
sternal plates, flat and rugose distal surfaces of the metacarpals,
medial curvature of the proximal femur, posterior shallow fossa of the
astagalus undivided, and mediolaterally expanded distal tibia. The
gracile long bones further support placement within non-saltasaurine
titanosaurs. Bonitasaura provides additional osteological data that
will contribute to a better resolution of titanosaur phylogeny.