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Simosaurus (Triassic sauropterygian) growth

Ben Creisler

A new online paper:

Nicole Klein & Eva Maria Griebeler (2015)
Bone histology, microanatomy, and growth of the nothosauroid
Simosaurus gaillardoti (Sauropterygia) from the Upper Muschelkalk of
southern Germany/Baden-Württemberg.
Comptes Rendus Palevol (advance online publication)

Simosaurus gaillardoti was a large eosauropterygian (Sauropterygia), a
group of diverse diapsid marine reptiles. Its occurrence correlates to
transgression phases in the Germanic Basin and a former morphological
study hypothesized that Simosaurus was capable of sustained swimming.
Microanatomical analysis of five long bones revealed functional
differences between the humerus and femur but did not confirm
sustained swimming in Simosaurus. It had certain active swimming
abilities but – based on microanatomy – it was a less efficient
swimmer when compared to contemporaneously living nothosaurs.
Simosaurus grew with well-vascularized coarse parallel-fibred bone
tissue. Growth marks appear as broad zones and thin annuli. Two
specimens show an external fundamental system in their outer cortex.
For three samples the logistic growth model best describes growth in
Simosaurus. The estimated ages at death range between 7 and 13 years,
asymptotic masses range between 113 and 129 kg and were reached after
10 up to 20 years. Maximum growth rates were between 44 and 69 g per
day, and higher than of an extant similar-sized reptile such as
Varanus komodoensis, Alligator mississippiensis, and Caretta caretta,
but are still consistent with the variability seen in extant reptiles.
Growth of one femur followed the von Bertalanffy model but the model's
biological reliability is questionable due to an unrealistic high
hatchling mass.