12 mai 2015

Llallawavis scagliai

Une nouvelle espèce d'oiseaux terreur vient d'être découverte:

Now paleontologists have unearthed one of the most complete fossils of a phorusrhacid to date. The skeleton of the new species, dubbed Llallawavis scagliai, is approximately 95% complete, giving scientists the ability to study a terror bird’s anatomy in unprecedented detail. 

(...) The fossil, which is missing only a few wing and toe bones and the tip of its stubby tail, was excavated in northeastern Argentina in 2010 from material laid down as sediment about 3.5 million years ago. L. scagliai likely lived in an open environment, possibly a grassland or a sparse forest through which small rivers flowed, says Federico Degrange, a paleo-ornithologist at the National University of Córdoba in Argentina and lead researcher on the study.

The new species of terror bird weighed an estimated 18 kilograms (about 40 pounds) and stood about 1.2 meters (4 feet) tall, Degrange’s team reports in the current issue of the Journal of Vertebrate Paleontology. That’s a moderate size for a terror bird, Degrange notes; at least one other species in the group grew more than 2 meters tall and weighed 70 kg or more.

Unlike most birds, many of the joints between bones in a terror bird’s skull are typically fused, Witmer says. In this species, the joints in the birds’ upper palate, as well as some of those near the beak, are much less flexible than they are in other types of birds, which may have helped them pummel their prey and more effectively rip apart carcasses.

But the most interesting information from the new fossil came from CT scans of its inner ear. The shape and orientation of the semicircular canals in that structure suggest the bird could swivel its head quickly, as it might when tracking or striking at prey, Degrange says. 



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