Bone histology of aquatic reptiles: what does it tell us about secondary adaptation to an aquatic life?

Abstract

Aquatic reptiles are very diversified in the fossil record. The description and pooling of certain bone histological features (collagenous weave and vascular network) of the various groups of aquatic reptiles highlight what this histological information can tell us about the process of secondary adaptation to an aquatic life. Notably, they show the absence of interaction between these histological features on the one hand and body size, mode of swimming, type of microanatomical specialization and phylogeny on the other. These histological features in aquatic reptiles seem to essentially provide information about the growth rate and basal metabolic rate of these taxa. The growth rate seems to have been rather high in most marine reptiles, when compared with terrestrial ectotherms. Moreover, distinct metabolic abilities are suggested. Indeed, various groups probably displayed a peculiarly high body temperature, and some show trends towards endothermy. This study also emphasizes the crucial need for homologous comparisons in histology and shows that much remains to be done to better understand the relationship between histological features, growth rate and metabolism in extant taxa in order to make inferences in the fossil groups. © 2012 The Linnean Society of London, Biological Journal of the Linnean Society, 2012, ●●, ●●–●●.

Preliminary observations on the bone histology of the Middle Triassic pseudosuchian archosaurBatrachotomus kupferzellensisreveal fast growth with laminar fibrolamellar bone tissue

“…In Mesozoic diapsids, the variety of combinations among bone tissues and vascular systems (e.g., Ricql es et al, 2003Ricql es et al, , 2008Chinsamy-Turan, 2005;Botha-Brink and Smith, 2011;Sander et al, 2011;Houssaye, 2013;Erickson, 2014;Houssaye et al, 2014;Klein et al, 2015aKlein et al, , 2015b) documents a much higher histological diversity that correlates with various growth patterns and life history strategies, as well as an implied broader metabolic range/diversity than observed in modern tetrapods (e.g., Castanet et al, 1993;K€ ohler et al, 2012). Ichthyosaurs (Buffr enil and Mazin, 1992;Houssaye et al, 2014) and some Sauropterygia (Buffr enil and Mazin, 1990;Wiffen et al, 1995;Klein et al, 2015a) are so far the only known non-archosaur diapsids that formed FLB throughout most of their ontogeny, which might be related-at least in Triassic forms-to a constant warm environment.…”

A Middle Triassic pachypleurosaur (Diapsida: Eosauropterygia) from a restricted carbonate ramp in the Western Carpathians (Gutenstein Formation, Fatric Unit): paleogeographic implications

“…The European pachypleurosaurs are assumed to be anguiliform swimmers (e.g., Caroll & Gaskill 1985;Lin & Rieppel 1998;Houssaye 2012), but with the inability to dive deeply (Rieppel 1989). Moreover, it has been suggested that the forelimbs of small European pachypleurosaurs are also used for terrestrial locomotion (Sander 1989;Lin & Rieppel 1998).…”

Mesozoic marine reptile palaeobiogeography in response to drifting plates

“…Plesiopedal and hydropelvic mosasauroids (with terrestrial-like limbs but no sacrum), are medium sized forms (1.5-3 m long), known only in the Middle Turonian of Morocco and Texas (Bardet et al, 2003;Bell and Polcyn, 2005). They are considered as more active swimmers than the plesiopelvic forms but still not efficient pelagic swimmers (Houssaye, 2008;Houssaye et al, 2013a). Finally, hydropedal and hydropelvic mosasauroids (with flippers and no sacrum), the 'true mosasaurids', were large (3-15 m long) open-sea active swimmers able to cross large oceanic realms (Houssaye et al, 2013a).…”

“…They are considered as more active swimmers than the plesiopelvic forms but still not efficient pelagic swimmers (Houssaye, 2008;Houssaye et al, 2013a). Finally, hydropedal and hydropelvic mosasauroids (with flippers and no sacrum), the 'true mosasaurids', were large (3-15 m long) open-sea active swimmers able to cross large oceanic realms (Houssaye et al, 2013a). They exhibited large powerful flippers and often a hypocercal tail increasing swimming performances, from an anguilliform to a thunniform locomotion (Lindgren et al, 2011(Lindgren et al, , 2013.…”