No Single ‘Missing Link’ Found In Dinosaur-To-Bird Evolution Process

Chuck Bednar for – Your Universe Online
The early stages of the process through which birds evolved from dinosaurs was slow and gradual, and there was no single “missing link” separating the two different types of creatures, according to research published in Thursday’s edition of the journal Current Biology.
Lead author Dr. Stephen Brusatte, a paleontologist at the University of Edinburgh in Scotland, and his colleagues analyzed the anatomical make-up of more than 850 body features in 150 extinct species in order to map the evolutionary journey from meat-eating dinosaurs to ancient birds. Based on the fossil records, they found that the emergence of birds took place bit-by-bit over the course of 150 million years.
“There was no moment in time when a dinosaur became a bird, and there is no single missing link between them,” Dr. Brusatte said in a statement. “What we think of as the classic bird skeleton was pieced together gradually over tens of millions of years. Once it came together fully, it unlocked great evolutionary potential that allowed birds to evolve at a super-charged rate.”
“Our study adds to a growing number of works that approach this problem from different angles, but all seem to confirm that the origin of birds was a truly special event in Earth history,” added Dr. Graeme Lloyd, a lecturer at the University of Oxford. “It is particularly cool that it is evidence from the fossil record that shows how an oddball offshoot of the dinosaurs paved the way for the spectacular variety of bird species we see today.”
According to Dan Vergano of National Geographic, birds are essentially defined by the unique traits that they possess – including feathers, hollow bones, a beak and a wishbone. While paleontologists previously believed that the 150-million-year-old Archaeopteryx, the earliest known bird, marked a massive evolutionary leap forward, research conducted over the past 20 years indicates that the avian characteristics had started showing up in dinosaurs far earlier.
The new study “confirms” the latter point-of-view, Vergano said, by discovering that “the dinosaur forebears of birds began gradually evolving avian traits almost as soon as dinosaurs appeared on Earth some 230 million years ago.” The research indicates that the first 80 million years of the evolutionary process occurred gradually, and was followed by “a burst of bird diversity” following the arrival and first powered flights of the Archaeopteryx.
“Once the whole body plan finally came together, then something was unlocked and they started evolving really fast,” Dr. Brusatte told Vergano, with Oxford colleague Roger Benson adding that the study provided “statistical confirmation of a view about bird evolution that paleontologists have described for a while. Scientifically, it would have been crazier if they had shown birds appearing from dinosaurs all of a sudden out of nowhere.”
Though the process began slowly, it eventually reached a point where it exploded and produced thousands of species in a relatively short period of time, LiveScience reporter Tanya Lewis wrote on Thursday. This took place after the basic body-type of the bird had been established, and avian species began arising far more quickly than other types of dinosaurs – which supports a hypothesis put forth by US paleontologist George Gaylord Simpson in the 1940s that suggested that extreme bursts of evolution typically follow the origin of a new body type.
Lewis said the authors were uncertain what about birds made them so successful. Dr. Brusatte suggested that their prosperity might have been due to the fact that they were small, warm-blooded and quick-moving, but that is only speculation. “But the researchers really don’t know why avians outperformed their comrades,” Lewis added. “You might as well ask why Homo sapiens were so successful, compared with other human relatives.”