It gained more steam when researchers discovered a set of fossilized footprints in 100-million-year-old Dakota sandstone in western Colorado that revealed the way the ancient creatures moved.
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“These are the first sites with evidence of dinosaur mating display rituals ever discovered, and the first physical evidence of courtship behavior”, study author Martin Lockley, professor of geology at UC Denver, said in a press release.
Researchers say they’ve found proof of an excited mating custom by dinosaurs: long furrows in the ground carved by the pawing of ripped at feet.
Writing online today in Scientific Reports, the team argues that the scrapes closely resemble those made by ground nesting birds-such as the Atlantic puffin and some species of plovers and parrots-that engage in “very energetic” courtship displays, which include lots of prancing around and scratching the ground.
Some birds show that behavior now, and the researchers believe the discovery shows that two-legged, meat-eating dinosaurs did it about 100 million years ago.
The scrapes were found to correspond to a typical kind of behavior known as “nest scrape display” or “scrape ceremonies” among modern birds.
Since eons, males that are after female mates, have fought off rival males.
This behaviour is common in mammals and birds so, until now, scientists could only speculate about dinosaur mating rituals and assume any similarities. “Thus, inferences that dinosaurs, especially theropods, displayed behavior analogous to modern birds are intriguing but speculative”.
Unable to remove the scrapes from the rocks without damaging them, 3D images of the scrapes were created and have been stored in the Denver Museum of Nature & Science. He provides evidence in the study that the scrape marks are not from actual nests, nor simply examples of digging for shelter, food or water.
According to the researchers, the four sites where they found the scratch marks could have been leks where groups of theropod males would gather to strut their stuff for an appreciative female audience.
Williamson agreed that dinosaur behavior must have been similar to birds and their other closest living relatives, crocodilians.
But, the new study suggests that dinosaur mating displays may have looked a lot like those of birds, in which males often use impressive plumage or complex dances to impress a mate. That makes it less likely, he says, that the behavior was “widespread and ubiquitous” in their extinct dinosaur ancestors.
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Paleontologists found scores of these “scrapes”, areas in the rock that were shallowly scarred by multiple scratch marks. He and his colleagues noticed the similarity between these marks and those made by courting birds, and said it was like finding a “fossilized… disco floor”.
