Contributions to Zoology, 84 (1) 59-84 (2015) Long bone histology and microanatomy of Placodontia (Diapsida: Sauropterygia) Nicole Klein1, 5, Alexandra Houssaye2, James M. Neenan3, 4, Torsten M. Scheyer3 1Staatliches Museum für Naturkunde Stuttgart, Rosenstein 1, 70191 Stuttgart 2UMR 7179 CNRS/Muséum National d’Histoire Naturelle, Département Ecologie et Gestion de la Biodiversité, 57 rue Cuvier CP-55, 75000 Paris, France 3Paläontologisches Institut und Museum, Universität Zürich, Karl Schmid-Strasse 4, CH-8006 Zurich, Switzerland 4The Function, Evolution and Anatomy Research (FEAR) Lab; School of Environmental and Rural Science; Univer- sity of New England, Armidale NSW 2351, Australia 5 Email:
[email protected] Key words: bone mass increase, bone tissue types, extinct marine reptiles, high growth rates, PCA, swimming capa- bilities, Triassic Abstract Henodus, Placodontia indet. aff. Cyamodus, non-armoured Pla- codus, and Placodontia indet. Bone tissue of Psephoderma and Placodontia, an enigmatic group of durophagous and in part Paraplacodus indicates low growth rates and a low basal meta- heavily armoured animals, were members of Sauropterygia, the bolic rate, as many modern sauropsids have such as the marine most diverse and successful group of Mesozoic marine reptiles. iguana, whereas the others grew with extremely fast growth Microanatomy and histology of long bones of several armoured rates, more typical for birds and mammals, indicating an in- and non-armoured Placodontia were studied, covering most of creased basal metabolic rate. their taxonomic breadth, to elucidate the paleoecology, physiol- ogy, and lifestyle of its members. Results reveal an unexpected and not phylogenetically or stratigraphically related disparity of microanatomical and histological features for the group.