An ancient bird that swam in Antarctica’s balmier waters 69 million years ago may be the earliest known waterfowl on Earth, scientists say.
A newly discovered and nearly complete fossilized skull found in rocks on the Antarctic peninsula belonged to Vegavis iaai, an ancient bird previously known only from fossilized body parts and a bit of its voice box. This skull offers the best evidence yet that the enigmatic, controversial bird was closely related to modern ducks and geese, report paleontologist Christopher Torres of the University of the Pacific in Stockton, Calif., and his colleagues in the Feb. 6 Nature.
The skull, dated to between 69.2 and 68.4 million years old, has numerous modern birdlike features, including a toothless beak and a small upper jaw. The bird’s braincase was also large, with the optic lobes — the brain structures that analyze visual information — shifted downward, similar to their position in modern birds. It’s an evolutionary shift that gives modern birds a leg up in navigation as well as hunting, providing more sensitive vision and motor coordination. V. iaai, the team suggests, was probably a pursuit hunter, diving for fish in the waters of Cretaceous Era Antarctica.
Birds were the only dinosaurs to survive the end-Cretaceous mass extinction event. Antarctica, far from the Chicxulub asteroid’s impact site off the current coast of Mexico’s Yucatán Peninsula, may have been a refuge for some ancestors of modern birds, allowing them to weather the ensuing environmental upheaval elsewhere around the globe.
V. iaai was first described about 20 years ago, from an Antarctic fossil dating to between 66 million and 68 million years ago. Researchers suspected then that the bird was closely related to modern waterfowl like ducks and geese. One bit of evidence that this late Cretaceous bird had some modern avian traits was the remains of a syrinx, a bird’s voice box. The fossil contained mineralized rings of collagen that would have anchored vibrating membranes, allowing the bird to — for example — honk.
But previous fossils of the bird didn’t include much of the skull. That hampered scientists’ ability to assess where exactly V. iaai fits in birds’ family tree — whether it was a primitive form with a few waterfowl-like traits, or whether it can be considered a wholly modern bird, one that lived alongside the nonavian dinosaurs.
The new skull does provide rare insight into bird skull anatomy just before the extinction event, says Daniel Field, a paleontologist with the University of Cambridge who was not an author on the study. “I love this fossil. It’s very exciting.”
But it also raises more questions than it answers, Field says. Based on these findings, “V. iaai may well be a very modern anseriform,” the scientific term for a waterfowl, he says. But he’s not convinced that the authors of the study have definitively proven their case. “The skull really looks even less ducklike than might have been expected,” he says. “They might be looking at it a bit through ‘teal-colored’ glasses.”
The bottom line is that these creatures lived a long time ago, and it’s incredibly hard to sort out the relationships of ancient birds from such scant fossil evidence. “The features that the new study identifies as evidence of modernity might also be traits shared by the more primitive forms of these birds, Field says. “It’s important to acknowledge that uncertainty.”
