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Cretaceous Kem Kem Beds (Morocco) unbalanced food web with dinosaurs

From: Ben Creisler

A new online paper:

Läng Emilie, Boudad Larbi, Maio Laszlo, Samankassou Elias, Tabouelle
Jérôme, Tong Haiyan & Cavin Lionel (2013)
Unbalanced food web in a Late Cretaceous dinosaur assemblage.
Palaeogeography, Palaeoclimatology, Palaeoecology (advance online publication)
DOI: http://dx.doi.org/10.1016/j.palaeo.2013.04.011,

The rich assemblage of continental vertebrates from the Cenomanian Kem
Kem Beds (Morocco) is one of the best known and most diversified for
the mid Cretaceous period (Cenomanian). This assemblage, however,
shows apparent ecological oddities, in particular the overabundance of
theropod dinosaurs versus plant-eating dinosaurs. Several hypotheses
have been proposed to explain this unbalanced ratio, including a
peculiar ecosystem, non-systematic collecting, taphonomic factors,
stratigraphic uncertainties and/or behavioral aspects of the dinosaur
groups concerned. Except the comparison of proportions of taxa between
field and shop data (McGowan and Dyke, 2009), the other hypotheses
have not been tested so far because of the lack of accurately measured
sections and systematically collected field data. Based on new field
data, we test the above-mentioned hypotheses. The analysis is focused
on the ratio of plant-eating versus carnivorous dinosaurs.

This dataset confirms the unbalanced ratio; moreover, the
stratigraphic distribution of fossils is quantitatively not
homogeneous and consequently important to avoid time-averaging, i.e.
the mixing of fossils of different ages together into a single unit.
The origin of the unbalanced food web among dinosaurs is related
neither to non-systematic collecting, nor to stratigraphic biases. The
palaeoenvironment seems to be the only likely factor to explain the
significantly high proportion of carnivorous versus plant-eating
dinosaurs. Indeed, the deltaic palaeoenvironment offered unfavourable
conditions for the setting of stable terrestrial vegetation but
favoring aquatic life. This aquatic life formed the basic level of an
aquatic or semi-aquatic food web, which directly fed top predators,
such as theropods in general and spinosaurs in particular.