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Re: Decompression syndrome in ichthyosaurs



> B. M. Rothschild, Z. Xiaoting and L. D. Martin (2012)
> Adaptations for marine habitat and the effect of Triassic and Jurassic
> predator pressure on development of decompression syndrome in
> ichthyosaurs.
> Naturwissenschaften (advance online publication)
> DOI: 10.1007/s00114-012-0918-0
> http://www.springerlink.com/content/q498172437420366/


The paper may partly explain why ichthyosaurs never (as far as we
know) radiated into the niches occupied by large, suspension-feeding
cetaceans.

In the Mesozoic, the giant suspension-feeders were fishes, not marine tetrapods:


Friedman M. (2012) Parallel evolutionary trajectories underlie the
origin of giant suspension-feeding whales and bony fishes. Proc Biol
Sci. 279: 944-951.

Abstract:
"Giant suspension feeders such as mysticete whales, basking and whale
sharks, and the extinct (indicated by '†') †pachycormiform teleosts
are conspicuous members of modern and fossil marine vertebrate faunas.
Whether convergent anatomical features common to these clades arose
along similar evolutionary pathways has remained unclear because of a
lack of information surrounding the origins of all groups of
large-bodied suspension feeders apart from baleen whales. New
investigation reveals that the enigmatic ray-finned fish †Ohmdenia,
from the Lower Jurassic (Toarcian, 183.0-175.6 Ma) Posidonia Shale
Lagerstätte, represents the immediate sister group of edentulous
†pachycormiforms, the longest lived radiation of large vertebrate
suspension feeders. †Ohmdenia bisects the long morphological branch
leading to suspension-feeding †pachycormiforms, providing information
on the sequence of anatomical transformations preceding this major
ecological shift that can be compared to changes associated with the
origin of modern mysticetes. Similarities include initial
modifications to jaw geometry associated with the reduction of
dentition, followed by the loss of teeth. The evolution of largest
body sizes within both radiations occurs only after the apparent onset
of microphagy. Comparing the fit of contrasting evolutionary models to
functionally relevant morphological measurements for whales and
†pachycormiform fishes reveals strong support for a common adaptive
peak shared by suspension-feeding members of both clades."