Product Code Database
Andalgalornis is a genus of flightless of the extinct family Phorusrhacidae (often called "terror birds") that lived in Argentina. The type species and only species is A. steulleti.
The following cladogram shows the position of Andalgalornis following a 2015 analysis:
Alvarenga and Elizabeth Höfling made some general remarks about phorusrhacid habits in a 2003 article. They were flightless, as evidenced by the proportional size of their wings and body mass, and wing size was more reduced in larger members of the group. They pointed out that the narrowing of the pelvis, upper maxilla, and thorax may have been adaptations for hunting in regions with high vegetation, which would permit greater agility when moving between vertical obstacles. The narrow upper maxilla would also help catching small animals hidden among tree trunks or stones. The large expansions above the eyes formed by the lacrimal bones (similar to what is seen in modern ) would have protected the eyes against the sun, and enabled keen eyesight, which indicates they hunted by sight in open, sunlit areas, and not shaded forests.
A 2010 study by Degrange and colleagues of Andalgalornis, based on Finite Element Analysis using , estimated its bite force and stress distribution in its skull, and showed that it had lost a large degree of intracranial immobility (mobility of skull bones in relation to each other), as was also the case for other large phorusrhacids. These researchers interpreted this loss as an adaptation for enhanced rigidity of the skull, and compared to the modern red-legged seriema and white-tailed eagle, the skull of the phorusrhacid showed relatively high stress under sideways loadings, but low stress where force was applied up and down, and in simulations of "pullback". Due to the relative weakness of the skull at the sides and middle, these researchers considered it unlikely that Andalgalornis engaged in potentially risky behavior that involved using its beak to subdue large, struggling prey. Instead, they suggested that it either fed on smaller prey that could be killed and consumed more safely, by, for example, swallowing it whole, or that when targeting large prey, it used a series of well-targeted repetitive strikes with the beak, in an "attack-and-retreat" strategy. Struggling prey could also be retained with the feet, despite the lack of sharp talons.
A 2012 follow-up study by Tambussi and colleagues analyzed the flexion abilities of the neck of Andalgalornis, based on the morphology of its neck vertebrae, finding the neck to be divided into three sections. They concluded that the neck musculature and skeleton of Andalgalornis was adapted to carrying a large head, and for helping it rise after a maximum downwards strike, and the researchers assumed the same would be true for other large, big-headed phorusrhacids. A 2020 study of phorusrhacid skull morphology by Degrange found that there were two main morphotypes within the group, derived from a seriema-like ancestor; the "Psilopterine Skull Type", which was plesiomorphic (more similar to the ancestral type), and the "Terror Bird Skull Type", which included Andalgalornis and other large members, that was more specialized, with more rigid and stiff skulls. Despite the differences, studies have shown the two types handled prey similarly, while the more rigid skulls and resulting larger bite force of the "Terror Bird" type would have been an adaptation to handling larger prey.
|
|
