New insights into the respiration and metabolic physiology of Lystrosaurus

Laaß, M., Hampe, O., Schudack, M., Hoff, C., Kardjilov, N. and Hilger A. (2010). New insights into the respiration and metabolic physiology of Lystrosaurus. —Acta Zoologica (Stockholm) 92: 363–371. The first examination by neutron tomography of a skull of Lystrosaurus declivis (Therapsida, Anomodontia) from the Lower Triassic of South Africa showed complexly constructed cartilaginous maxilloturbinals in the nasal cavity. They were situated directly in the respiratory air flow and fill out most of the ventral part of the nasal chamber. Because maxilloturbinals in extant mammals and birds serve as a countercurrent exchange system for thermoregulation and humidification, their presence in the anomodont Lystrosaurus suggests strongly that Lystrosaurus was already endothermic. The endothermic metabolism allowed Lystrosaurus to tolerate high ambient temperature fluctuations. The complexly constructed maxilloturbinals could have reduced respiratory water loss because of higher ventilation rates in drought conditions in the Karoo basin.