Did dinosaur feathers attract mates?

It looks like a modern-day crow. But it’s a 120 million year old four-winged dinosaur called a Microraptor. What’s more, studies of dinosaur feathers indicate that the purpose of these iridescent ones may have been to attract mates.

Like a crow, the Microraptor had iridescent black feathers. But unlike a crow, the Microraptor’s tail was narrow, exhibiting a pair of streamer feathers. Indeed, this configuration suggests the importance of display in the early evolution of feathers. Scientists reporting the findings supporting this idea in March 2012 in the journal Science.

To determine the color of the Microraptor’s feathers, the researchers compared the patterns of pigment-containing organelles from a Microraptor fossil to those in modern birds. In addition, they also determined that the dinosaur’s plumage was iridescent with a glossy sheen like the feathers of a modern crow.

Discovered as the first four-winged dinosaur in 2003, Microraptor is at the center of questions about the evolution of feathers and flight.

Notably, scientists first thought the tail feathers to be a broad, teardrop-shaped surface, or with a shape more like that of a paper airplane. In other words, that shape could have helped generate lift. But Microraptor’s tail fan is actually much narrower with two elongate feathers off its tip.

But now, the researchers believe the tail feathering may have been ornamental. Like many other ornamental features in birds and other creatures it could have evolved for courtship and other social interactions. Therefore, the feathers are not an adaptation for flight.

Julia Clarke is a paper co-author and paleontologist at The University of Texas at Austin. She said:

Most aspects of early dinosaur feathering continue to be interpreted as fundamentally aerodynamic, optimized for some aspect of aerial locomotion.

Clearly, some of these structures were ancestral characteristics that arose for other functions and stuck around. In contrast, others might have been displays or signals of mate quality.

Clarke believes that feather features were shaped by early locomotor styles.

But, as any birder will tell you, feather colors and shapes may also be tied with complex behavioral repertoires and, if anything, may be costly in terms of aerodynamics.

Modern birds use feathers for many different things. Flight is only one. Two more are thermoregulation and mate-attracting displays. Matt Shawkey, a paper co-author and biologist at the University of Akron, said:

Iridescence is widespread in modern birds, and is frequently used in displays. The evidence that Microraptor was largely iridescent suggests that feathers were important for display even relatively early in their evolution.

Information on the feather color of a variety of dinosaurs has recently come to light.

The first color map of an extinct dinosaur showed black-and-white spangles, red coloration and grey body color in a species called Anchiornis.

Finally, the new data from Microraptor and other findings show a complex color repertoire that includes iridescence. They are likely ancestral to a group of dinosaurs called Paraves that originated at least 140 million years ago. It includes dinosaurs like Velociraptor as well as Archaeopteryx, Anchiornis and living birds.

Bottom line: A March 2012 report in the journal Science describes the feathers of the Microraptor, a four-winged dinosaur that lived 120 million years ago. The Microraptor’s tail, narrow and adorned with a pair of streamer feathers, may have attracted mates. Scientists believe this implies the importance of display in the early evolution of feathers.

Read more from the National Science Foundation

March 9, 2012

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