Insights into Argentavis magnificens (Aves, Teratornithidae) lifestyle based on neuroanatomy

Teratornithidae is an extinct bird family, likely related to Cathartidae, known exclusivelyfrom the Americas. They were once thought to be scavengers, but recent theoriessuggest they were opportunistic or piscivorous birds capable of swallowing preywhole. The most notable species, Argentavis magnificens, had a wingspan of 6 to 8m and weighed 70 to 80 kg. In order to infer paleobiological aspects of this bird, itsendocast (as a proxy for brain morphology), reconstructed from computed tomographyscans of the holotype skull, is here described and compared to that of otherbird species of zoophagous feeding habits with different flight styles. The brain ofArgentavis presents a general appearance similar to that of Cathartidae, being dorsoventrallyflattened and anteroposteriorly elongated, with small optic lobes in relationto the total encephalic surface. The estimated volume of the bulbi olfactorii is verysimilar to that of the Andean Condor Vultur gryphus. The main difference observedwith Cathartidae is the marked development of the eminentiae sagittales present inArgentavis (structures closely related to the perception of visual information), whichare more similar to those of the Accipitriformes and Falconiformes analyzed. The resultsobtained here suggest that Argentavis was a scavenger or even maybe a kleptoparasiticbird, relying more on vision than on smell (similar to that observed in theAndean Condor). Furthermore, the inner ear and flocculi exhibit characteristics similarto birds without acrobatic flight, indicating that Argentavis had a soaring flight andinhabited open areas without much vegetation.