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Europasaurus (Jurassic sauropod) skull (free pdf)



From: Ben Creisler
bcreisler@gmail.com

A new online paper in open access:

Jean Sebastian Marpmann, José Luis Carballido, P. Martin Sander & Nils
Knötschke (2014)
Cranial anatomy of the Late Jurassic dwarf sauropod Europasaurus
holgeri (Dinosauria, Camarasauromorpha): ontogenetic changes and size
dimorphism.
Journal of Systematic Palaeontology (advance online publication)
DOI:10.1080/14772019.2013.875074
http://www.tandfonline.com/doi/full/10.1080/14772019.2013.875074#.UzQ89vldXeI

Sauropods were the most successful herbivorous group of dinosaurs
during the Mesozoic era. Despite their supremacy as reflected in the
fossil record, sauropod skulls are very rare and current knowledge of
skull anatomy is based on just a few taxa. Juvenile skull bones are
even rarer than adult skulls; thus, our understanding of their
morphology and ontogenetic changes is limited. The recent discovery of
several adult and juvenile specimens of a Late Jurassic taxon from
Germany, Europasaurus holgeri, extends our knowledge of sauropod skull
anatomy. A total of 123 skull bones, representing at least 14 skulls,
were examined, described and compared to other taxa. The skull
material includes several individuals of various ontogenetic stages.
Because size alone is not sufficient to determine the morphological
ontogenetic stage (MOS), size-independent characters were used to
stage the bone elements. Detailed studies of the skull bones proved
that the material represents two morphotypes, independent of
ontogenetic stage. Since the original description of Europasaurus, new
skull material has been found, and an updated skull reconstruction of
an adult individual is presented here. All the autapomorphic
characters of Europasaurus recognized in the skull (i.e.
anteroposteriorly long and lateromedially narrow frontal; presence of
postparietal fenestra; large participation of the jugal to the ventral
rim of the skull and the orbit; presence of a postparietal foramen and
single optic foramen) are plesiomorphic characters of basal
sauropodomorphs and/or present in embryos and juvenile sauropods.
Therefore, we consider that in Europasaurus these characters evolved
through paedomorphosis, which resulted in the dwarf condition of this
taxon.