Paleohistological Analysis of “Terror Birds” (Phorusrhacidae, Brontornithidae): Paleobiological Inferences

Extinct flightless birds of the clades Phorusrhacidae and Brontornithidae areamong the most characteristic elements of the South American Cenozoic faunas. Althoughthe anatomy, systematics, paleoecology, and distribution of these birds have been analyzed insome detail, there is not a single work dealing with the osteohistology of these taxa. Herein,we present for the first time paleohistological data for phorusrhacids (Patagornis marshi) andbrontornithids (Brontornis burmeisteri). A dense vascularized fibrolamellar matrix and anuninterrupted cortex lacking growth lines indicate similar metabolism and physiologicalattributes occurring in most extant birds, and they differ from the condition of insulartaxa or species living in very stable habitats. This is congruent with recent analysesindicating that phorusrhacids were very active birds lacking insularity-related attributes.It also supports recent growing evidence indicating that these birds’ extinction may berelated to climatic and environmental changes rather than being the result of competitivedisplacement by immigrant placental mammals. Fil: García Marsa, Jordi Alexis. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales "Bernardino Rivadavia"; Argentina Fil: Agnolin, Federico. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales "Bernardino Rivadavia"; Argentina