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Cretaceous shallow marine squamates with bone mass increase



From: Ben Creisler
bcreisler@gmail.com


A new online paper:


Alexandra Houssaye (2012)
Palaeoecological and morphofunctional interpretation of bone mass
increase: an example in Late Cretaceous shallow marine squamates.
Biological Reviews (advance online publication)
DOI: 10.1111/j.1469-185X.2012.00243.x
http://onlinelibrary.wiley.com/doi/10.1111/j.1469-185X.2012.00243.x/abstract



Bone mass increase (BMI; i.e. osteosclerosis with possible additional
pachyostosis) is characteristically displayed by many Late Cretaceous
squamates that adapted to shallow marine environments—plesiopelvic
mosasauroids, stem-ophidians and pachyophiids. A combined
morphological and microanatomical analysis of vertebrae and, to a
lesser extent, ribs of these fossil squamates provides new data about
the distribution and variability of this osseous specialization in
these taxa. Classical thin sections and third generation synchrotron
microtomography and laminography were used for the microanatomical
analysis. Following the explanation of the likely involvement of this
specialization in the control of buoyancy, body trim and Carrier's
constraint, new palaeoecological inferences and new hypotheses about
the locomotor abilities and life environment of these organisms are
produced. The taxa displaying BMI are considered to have undertaken
long dives, hovering slowly and maintaining a horizontal trim, in
shallow and protected water environments. Conversely, marine
stem-ophidians deprived of this specialization are regarded as slow
surface swimmers able to live in more open marine environments. This
study highlights the importance of microanatomical data for
palaeoecological studies. It also discusses the significance of the
use of this specialization as a character in phylogenetic studies.