Utatsusaurus and early ichthyosaur biology

[Ben Creisler <bcreisler@gmail.com>]

From: Ben Creisler
bcreisler@gmail.com

A new online paper:

Yasuhisa Nakajima, Alexandra Houssaye, and Hideki Endo (2012)
Osteohistology of Utatsusaurus hataii (Reptilia: Ichthyopterygia):
Implications for early ichthyosaur biology.
Acta Palaeontologica Polonica (in press)
doi: http://dx.doi.org/10.4202/app.2012.0045
http://app.pan.pl/article/item/app20120045.html



Ichthyosaurs were highly adapted to a marine lifestyle, as shown by
their fish-like body shape and their assumed active swimming abilities
and high metabolic rates. However, the processes of adaptation to an
aquatic life in the early stages of this lineage remain poorly
understood. Here, we present the first osteohistological data
concerning the most basal ichthyopterygian yet known, Utatsusaurus
hataii, from the Lower Triassic of Japan. The cancellous bone
structure suggests adaptation to active swimming in an open marine
environment. Moreover, the possible occurrence of rapidly deposited
bone tissue, in a fibrolamellar complex, suggests a higher metabolic
rate than in modern poikilothermic reptiles, and therefore a trend
toward homeothermy. This basal ichthyosaur, with its elongate body,
was already more adapted to an aquatic lifestyle than expected from
its morphology, and the process of adaptation to a marine lifestyle
was already well advanced by the Early Triassic.