Paleontologist after more evidence that relatives of modern birds co-existed with dinosaurs
Posted January 21, 2011
The theory that close relatives of modern birds once co-existed with non-avian dinosaurs before a mass extinction 65 million years ago had trouble flying with many paleontologists until about five years ago.
That was when a team of scientists announced that new data from fossils discovered in Antarctica in the 1990s by Argentine researchers offered evidence that at least one species related to modern birds shared the same space and time with dinosaurs. [See previous article: Antarctic bird nest?]
Julia Clarke was the lead author of that Nature paper, with the bold title “First definitive fossil evidence for the extant avian radiation in the Cretaceous.” Now Clarke, an associate professor of paleontology at the Jackson School of Geosciences at the University of Texas in Austin , hopes to get her hands on additional material from Antarctica that will fill in more of the story about the early spread of all living birds.
Toward that purpose she’ll join a team of paleontologists headed to a group of islands off the Antarctic Peninsula early next year led by Ross MacPhee , with the American Museum of Natural History in New York . [See related article: Reverse course.]
The fossil hunters include dinosaur and mammal experts. “It’s a group of vertebrate paleontologists that want to ask questions that only Antarctic fossils can answer,” Clarke said.
It will be Clarke’s first trip to the Antarctic, though her fieldwork has often taken her to the Southern Hemisphere and locations from Argentina to Peru to New Zealand. Her work in South America, in particular, has shed new light on penguin evolution. [See related article: Penguins of a feather.]
But it’s in Antarctica where she believes more evidence is waiting to be found to show that the ancestors of modern birds lived more than 65 million years ago. Most scientists believe an asteroid hit the Earth and caused a cataclysmic extinction. Non-avian dinosaurs disappeared, along with an estimated three-quarters of all species.
“For parts of and close relatives of the crown clade — relatives of living bird lineages — Antarctica is the place to go. And Vega, specifically, is the place to go — globally,” Clarke said.
Vega Island, a small island off the Antarctic Peninsula, has proven to be relatively rich with fossils from the Late Cretaceous, about 80 million to 65 million years ago. The asteroid impact, which marks the so-called K-T Boundary, is estimated to have occurred around 64 million years ago.
It was on Vega where the Argentine scientists found the specimen that Clarke and colleagues would later call Vegavis iaai, which falls within the order Anseriformes, which includes ducks, geese and swans.
Photo Courtesy: Julia Clarke
Vegavis iaai concretion, left, and the CT scan of the rock and bird fossils.
The rock specimen from Vega contained avian vertebrae and pelvic bones among other bits of skeleton. Clarke used a high-resolution X-ray CT scanner to see the fossils without breaking the rock and possibly damaging the material.
In spite of the Vega evidence, there is still contention among paleontologists of what lineages are present in the Cretaceous prior to the K-T boundary, according to Clarke.
In 2008, she and co-principal investigator Judd Case at Eastern Washington University received a Small Grant for Exploratory Research (SGER) from the National Science Foundation (NSF) to pull together data and experts on Antarctic fossils from the last 20 years to see if more evidence existed to support the theory of a robust modern radiation from Antarctica.
It’s a good start, Clarke said, but added, “What we really need are new specimens because some of the important material that Case and the Argentine teams collected during their field seasons can just hint at the bird species present.
“It is just the tantalizing beginning of what we need to know; we need to get better specimens. … There’s arguably no better material in the world than what’s come out of Vega so far. There’s a lot more work that can be done there.”
Hence the expedition to the islands of the Antarctic Peninsula, which requires a trip aboard a research vessel toward the end of the Southern Hemisphere summer in February. The scientists will make day trips to the islands from small inflatable boats, as well as work out of field camps on the islands for days at a time.
The researchers can expect long hours in cold conditions, sifting through rocks and dirt for the small fragments that might offer further clues about the ancient history of birds, mammals and dinosaurs.
For her part, Clarke is hesitant to state that Antarctica was ground zero for modern bird evolution — but she also doesn’t dismiss the possibility. “If we can increase our sampling globally, we can get a better sense of what role Antarctica played in the diversification of birds. We don’t know that it’s the area of origin,” she said.
“Finding bird fossils is always a rare occurrence, but based on what we specimens have been collected from Antarctica to date, work in this region has a high probability of success. In terms of spinning a roulette wheel of fossil discovery, if you will, I think it’s weighted in our favor in this case. I think we’re going to find more complete material if we can spend the time at the sites.”
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