Feb. 26, at 7 p.m. in Yates Hall, members of the Sperry-Gallagher Audubon Society gathered for their monthly meeting, welcoming newcomers and longtime bird enthusiasts alike. The chapter, affiliated with the National Audubon Society, meets on the last Thursday of each academic month and features guest speakers, seasonal bird discussions, and community updates.
Megan Corrigan was the evening’s speaker. Her topic, “How Birds Became Dinosaurs,” was meant to challenge people’s general assumptions about dinosaurs.
In general, many people grew up learning that dinosaurs were extinct, cold-blooded reptiles. Nowadays, most scientists agree that birds are not just related to dinosaurs, but actually are dinosaurs.
Corrigan explained how this change in thinking happened, citing the PBS Nova documentary “Dino Birds” as a main source. In the 1820s, early paleontologists thought huge fossil bones belonged to giant extinct reptiles. However, in 1860, the discovery of the Archaeopteryx, found in Germany, challenged this theory. This 150-million-year-old fossil contained both feathers and teeth, preserving a combination of bird and reptile features.
Later, paleontologist Thomas Henry Huxley said that birds were closely related to small theropod dinosaurs. But his idea was debated for many years, mostly because no dinosaur fossils had a wishbone, that being a signature feature of birds.
At the same time, fossils found in the United States added more clues. In the 1860s, ancient marine deposits in Kansas yielded remarkable fossils. One of them, found by Benjamin Franklin Mudge and described by Yale paleontologist Othniel Charles Marsh, was the Ichthyornis, a bird with teeth that resembles our gulls of today. This fossil, about 80 to 90 million years old, showed that early birds lived with non-avian dinosaurs.
This debate grew in the 1970s when paleontologist John Ostrom suggested that some theropods were warm-blooded. Their bone structure, the ratio of predators to prey, and the locations of fossils found in cold areas, all pointed to high metabolic rates. Shared features, such as a special wrist bone called the semi lunate carpal, also connected theropods and birds.
Later, a classification method called cladistics, which compares shared physical traits, further strengthened the connection. Many paleontologists now say that birds clearly belong within the theropod branch of the dinosaur family tree. Even so, some people remain skeptical.
Ornithologist Alan Feduccia believes the similarities may be due to convergent evolution, in which unrelated groups develop similar traits, such as wings in insects, bats and birds. He also questions the evidence from fossilized embryos, noting differences in how digits develop in bird embryos compared to those in theropod fossils.
New fossils keep changing what we know. In the 1990s, volcanic deposits in China were studied. Corrigan, referred to as the “Pompeii of dinosaurs,” revealed feathered dinosaurs that were not birds, like Yutyrannus. This suggests that feathers might have predated flight.
Modern technology has added even more evidence. CT scans of a 67-million-year-old skull called Asteriornis, also known as the “wonder chicken,” revealed features very similar to those of modern birds. Corrigan closes by stating that studies of collagen proteins suggest that the famous Tyrannosaurus rex’s closest living relatives are actually modern birds.
To close, Corrigan reminded everyone that “science is always changing.” Many paleontologists are sure that birds are living dinosaurs, but there is still some debate. This shows that scientists are always rethinking the evidence.