A near-perfect fossilized skull discovered in Antarctica reveals the bridge between prehistoric and modern birds, a new study has found.
The fossil is a specimen of a species called Vegavis iaai, which lived around 69 million years ago – more than 2 million years before the mass extinction that wiped out all non-avian dinosaurs.
It has a long pointed beak and a brain shape unlike any other Mesozoic birds, which were markedly different from species that would evolve into the class of feathered creatures we see around us today.
Ever since Vegavis was described 20 years ago, some paleontologists suspected the genus might be an early member of modern birds, within the order of waterfowl. Others doubted it since modern birds were extremely rare prior to the asteroid impact that triggered the end-Cretaceous extinction.
But they were missing what is arguably the most important piece of Vegavis, at least when it comes to taxonomy: a somewhat-intact skull.
“Few birds are as likely to start as many arguments among paleontologists as Vegavis,” says lead author Christopher Torres, a paleontologist from Ohio University.
“This new fossil is going to help resolve a lot of those arguments. Chief among them: where is Vegavis perched in the bird tree of life?”
Bird fossils can be quite delicate, and few from this time are preserved in such good shape as this one. All other Vegavis specimens found to date have been either skeletons sans head, or just bits of the skull.
The researchers suspect the species may have survived the mass extinction because of their Antarctic location, which would have offered a temperate climate with lush vegetation at a time when the rest of the world was quite uninhabitable.
“Elsewhere globally, the rapid environmental upheaval characterizing the K–Pg boundary is generally marked by similarly rapid replacement of stem birds by crown birds, followed by diversification of the latter early in the Palaeogene,” the authors write.
That makes V. iaii the best representative we have for the bridge between prehistoric and modern birds.
The researchers used X-ray micro-computed tomography to scan the skull and digitally reconstruct it in three dimensions, revealing details of its braincase, palate, rostrum and mandible, as well as its brain shape.
The specimen hints at features consistent with modern waterfowl, but unlike the ducks and geese of today, V. iaai also had a slender, pointed beak and powerful jaw muscles for snapping up fish: features that are more similar to those of diving birds of today like grebes and loons.
It has a well-developed salt gland in the nasal region of its beak, a feature that removes sodium chloride from the blood of some marine bird species with diets high in seafood and, consequentially, salt.
The rest of the fossil skeleton builds on this picture of V. iaai‘s aquatic lifestyle, with legs that positioned the feet to propel the bird through the water in pursuit of swimming prey.
“Those few places with any substantial fossil record of Late Cretaceous birds, like Madagascar and Argentina, reveal an aviary of bizarre, now-extinct species with teeth and long bony tails, only distantly related to modern birds,” says paleontologist Patrick O’Connor from Ohio University.
“Something very different seems to have been happening in the far reaches of the Southern Hemisphere, specifically in Antarctica.”
This research was published in Nature.
