Downloaded from rsbl.royalsocietypublishing.org on 13 July 2009 Biol. Lett. (2009) 5, 557–560 Postcranial skeletal pneumatization has been used to doi:10.1098/rsbl.2009.0139 infer the presence of air-sacs and flow-through venti- Published online 1 May 2009 lation in several extinct Mesozoic bird-line (i.e. Palaeontology ornithodiran) archosaur groups, including non-avian saurischian dinosaurs (e.g. O’Connor & Claessens 2005; O’Connor 2006; Wedel 2007, 2009; Sereno Postcranial skeletal et al. 2008), and pterosaurs (Britt 1993; Bonde & Christiansen 2003; Claessens et al. 2009). pneumaticity and air-sacs The distribution of PSP within and among ptero- saur species has received relatively little study, though in the earliest pterosaurs some major features and trends have been established Richard J. Butler1,*, Paul M. Barrett1 recently (Claessens et al. 2009). Previous authors and David J. Gower2 have been unable to identify unambiguous evidence of PSP in stratigraphically early non-pterodactyloid 1Department of Palaeontology, and 2Department of Zoology, The Natural History Museum, Cromwell Road, London SW7 5BD, UK pterosaurs, or ‘rhamphorhynchoids’, from the Late *Author and address for correspondence: Bayerische Staatssammlung fu¨r Triassic and earliest Jurassic (Britt 1993; Bonde & Pala¨ontologie und Geologie, Richard-Wagner-Straße 10, 80333 Munich, Christiansen 2003; Claessens et al. 2009, fig. 4). Germany (
[email protected]). Here we provide new evidence of PSP in Late Patterns of postcranial skeletal pneumatization Triassic and earliest Jurassic pterosaurs, demonstrating (PSP) indicate that pterosaurs possessed that PSP and, by inference, air-sacs were probably components of a bird-like respiratory system, present in the common ancestor of nearly all known including a series of ventilatory air-sacs.