Reconstructing the inner ear of early Pterosauria to decipher the origin of endothermy in the flying reptiles of the Mesozoic

Objective

REPTERMO asks when and how endothermy evolved in pterosaurs and early dinosaurs. Flight, rapid growth and filamentous integuments point to high metabolic rates in these clades, yet direct physiological inference from fossils remains difficult. REPTERMO will refine the Thermo-Motility Index (TMI), a biomechanical framework that uses morphometrics and functional models of the semicircular canals (SCC) to infer thermal physiology. A key gap is the lack of empirical data on ampullar stereocilia in living birds and reptiles; current parameters were extrapolated from a few modern species and likely bias SCC biomechanics and downstream estimates. The project aims to: i) reconstruct via Ct scanning the inner ears from early pterosaurs (e.g., Rhamphorhynchus), lagerpetids (e.g., Ixalerpeton) and dinosauromorphs (e.g., Silesaurus), expanded by focused fieldwork and museum visits; ii) describe stereocilia via histology in selected birds (e.g., Larus fuscus, Columba livia) and reptiles (e.g., Mauremys leprosa, Crocodylus niloticus) to quantify, for the first time, the cilia deflection factor (CDF); iii) integrate the substantial dataset of reconstructed inner ear and CDF measurements to recalibrate TMI and produce robust endothermy estimates across Ornithodira. By delivering the first empirically grounded link between SCC biomechanics and metabolic state in extinct reptiles, REPTERMO will locate the origin of hypothesised endothermy in the Late Triassic and help explain the early success of pterosaurs and dinosaurs. The results will strengthen paleoenvironmental reconstructions and stimulate evolutionary concepts, while advancing CT imaging, histology and quantitative 3D analysis with cross-disciplinary value. Hosted at Instituto Superior Técnico (IST, Lisbon) in Dr Araújo’s lab, the fellowship will deepen the researcher’s skills in biomechanics, metabolic evolution and statistics, consolidating a path to research leadership in vertebrate paleobiology.