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Plesiosaurs from Morocco



From: Ben Creisler
bcreisler@gmail.com


A new online paper:

Peggy Vincent, Nathalie Bardet, Alexandra Houssaye, Mbarek Amaghzaz &
Saïd Meslouh (2012)
New plesiosaur specimens from the Maastrichtian Phosphates of Morocco
and their implications for the ecology of the latest Cretaceous marine
apex predators.
Gondwana Research (advance online publication)
http://dx.doi.org/10.1016/j.gr.2012.11.011
http://www.sciencedirect.com/science/article/pii/S1342937X12003875


Several clades of marine tetrapods, including the apex predators
mosasaurs and plesiosaurs, disappeared during the mass extinction at
the end of the Cretaceous, about 65 My ago. The extreme fossil
richness of the Maastrichtian Phosphates of Morocco provides insights
into the systematic diversity of the latest mosasaurs where about ten
species are known. However, data of the coeval plesiosaurs are
comparatively scarce. Up to now, only one species, the elasmosaurid
Zarafasaura oceanis, is known. Here we describe new elasmosaurid
plesiosaur post-cranial material from the Maastrichtian of the Oulad
Abdoun Basin (Morocco) that provides new data about the taxonomical
and morphological diversity of plesiosaurs in this area. Most of the
new material consists of vertebrae that likely belong to a unique
elasmosaurid taxon and differ from all other elasmosaurids documented
so far. As Zarafasaura is known only from cranial material, it cannot
be determined whether the new material may be assigned to this taxon.
The new material shows that the latest Cretaceous plesiosaurs in this
low latitude area (about 20°N) were rather gracile, most likely
piscivorous taxa that occupied ecological niches similar to those of
rather small mosasaurs (e.g. Halisaurus and “Platecarpus” ptychodon)
but distinct from those of most coeval large mosasaur taxa. These
plesiosaur fossils are also remarkable in that they consist of both
juvenile and adult specimens, suggesting limited segregation between
individuals of different ontogenetic stage, a feature that might be
attributed to upwelling-related, high nutrient input and food
availability in this area during the Maastrichtian. Moreover, the
possible occurrence, with older specimens, of a neonate specimen - one
among the very few known worldwide - suggests a possible social
structure organization. The new data contribute to increase our
understanding of Late Cretaceous plesiosaur biodiversity and provide
new insights into the ecology of latest Cretaceous marine apex
predators.