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Titanosaurian Braincase from Cretaceous “Lo Hueco” Locality in Spain



Ben Creisler
bcreisler@gmail.com


New in PLoS ONE (open access):

Fabien Knoll , Lawrence M. Witmer, Ryan C. Ridgely, Francisco Ortega &
Jose Luis Sanz (2015)
A New Titanosaurian Braincase from the Cretaceous “Lo Hueco” Locality
in Spain Sheds Light on Neuroanatomical Evolution within Titanosauria.
PLoS ONE 10(10): e0138233.
doi:10.1371/journal.pone.0138233
http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0138233


Despite continuous improvements, our knowledge of the neurocranial
anatomy of sauropod dinosaurs as a whole is still poor, which is
especially true for titanosaurians even though their postcranial
remains are common in many Upper Cretaceous sites worldwide. Here we
describe a braincase from the uppermost Cretaceous locality of ‘‘Lo
Hueco” in Spain that is one of the most complete titanosaurian
braincases found so far in Europe. Although the titanosaurian
Ampelosaurus sp. is known from the same locality, this specimen is
clearly a distinct taxon and presents a number of occipital characters
found in Antarctosaurus and Jainosaurus, which are approximately
coeval taxa from southern Gondwana. The specimen was subjected to
X-ray computed tomographic (CT) scanning, allowing the generation of
3D renderings of the endocranial cavity enclosing the brain, cranial
nerves, and blood vessels, as well as the labyrinth of the inner ear.
These findings add considerable knowledge to the field of sauropod
paleoneuroanatomy in general and titanosaurian endocast diversity in
particular. Compared with that of many sauropodomorphs, the endocast
appears only slightly flexed in lateral view and bears similarities
(e.g., reduction of the rostral dural expansion) with Gondwanan
titanosaurians such as Jainosaurus, Bonatitan, and Antarctosaurus. The
vestibular system of the inner ear is somewhat contracted (i.e., the
radius of the semicircular canals is small), but less so than expected
in derived titanosaurians. However, as far as the new specimen and
Jainosaurus can be contrasted, and with the necessary caution due to
the small sample of comparative data currently available, the two taxa
appear more similar to one another in endocast morphology than to
other titanosaurians. Recent phylogenetic analyses of titanosaurians
have not included virtually any of the taxa under consideration here,
and thus the phylogenetic position of the new Spanish
titanosaurian—even its generic, let alone specific, identification—is
not possible at the moment. Nevertheless, both the braincase osteology
and the endocast morphology suggest that the specimen represents a
derived titanosaurian that presumably branched further from the base
of Lithostrotia, potentially even near Saltasauridae, comparable in
evolutionary terms with Jainosaurus.