Reconsidering the Birdlike Characteristics of Dinosaur Feathers

Despite not being able to fly as birds do nowadays, numerous dinosaurs possessing feathers may actually have had feathers more akin to those of modern birds than what was previously believed by scientists.

In 2019, researchers investigating fossils discovered that most feathers from a flightless dinosaur primarily consisted of a different and more flexible variety of keratin, the protein found in modern bird beaks, feathers, and scales. Scientists at the time hypothesized that feathers had evolved over time at the molecular level, becoming stiffer as birds — the only surviving dinosaurs — became airborne. (SN: 7/31/14).

However, the results could have been influenced by the fossilization process, which can alter feather proteins so they resemble different forms of keratin, according to research published in the October issue of Nature Ecology and Evolution. The same findings were also presented at the annual meeting of the Society for Vertebrate Paleontology in Cincinnati on October 19.

The research suggests the possibility that dinosaur feathers were predominantly composed of the beta-keratin proteins found in bird feathers. This discovery does not imply that all feathered dinosaurs could fly, but it opens up new discussions regarding the evolution of feathers.

This research also grants scientists insight into how the fossil record may transform over time, according to Julia Clarke, a vertebrate paleontologist at the University of Texas at Austin who was not part of the new study. She notes that there's much more to uncover about the chemical alteration that all structures experience during the processes of rock formation, liquification, and burial.

In the new study, paleontologist Tiffany Slater from University College Cork in Ireland and her team subjected modern bird feathers to heat conditions simulating the environment that deeply buried dinosaur feathers might have experienced during fossilization. The feathers' beta-keratins unfolded and reformed into alpha-keratins, the more flexible type that was previously found to be dominant in dinosaur feathers. This indicates a similar process may have occurred in dinosaur feathers.

Next, the team examined a bird feather roughly 50 million years old and a 125-million-year-old feather from the nonavian dinosaur Sinornithosaurus. The bird feather appeared to be primarily composed of alpha-keratins, leading the researchers to believe that the proteins transformed during fossilization, as the feather should have been rich in beta-keratins. On the other hand, the dinosaur feather seemed to be made up mostly of beta-keratins, indicating it may not have been exposed to enough heat to transform its proteins.

According to Slater, the most logical interpretation is that the distortions caused by fossilization misled previous researchers into believing that the molecular composition of dinosaur and bird feathers was quite different.

However, according to molecular paleontologist Mary Schweitzer from North Carolina State University in Raleigh, and one of the researchers involved in the study, the conditions explored in the new study may not accurately replicate what happens during centuries of burial.

Based on her own research, Schweitzer has found that feathers exposed to even higher temperatures manage to preserve their proteins effectively when left in sediment. She believes the effect of fossilization on feather proteins may be more complex and not yet fully understood.

Many scientists believe that feathers evolved not for the purpose of flight but to keep dinosaurs warm and assist in attracting mates (SN: 2/4/10). Though some non-avian dinosaurs could project themselves into the air and glide from location to location (SN: 10/28/16), there were others that could not fly but still flapped their wings while running (SN: 5/2/19).

Considering that feathers are only one factor in the evolution of flight, the composition of keratin may play a lesser part, according to Matthew Shawkey, a biologist at Ghent University in Belgium, who was not involved in this research. Shawkey asks whether a feather composed of alpha-keratin would indeed be so fragile. However, he acknowledges that the answer to this question remains uncertain.

He argues that the shape of feathers, the presence of veins in them, and their alignment relative to each other could be more critical for the evolution of flight.

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