Scientists discover dinosaurs’ dance marks in western Colorado, confirming sexual selection drives evolution

By on
The dinosaur named "Sue," a 41-foot-long Tyrannosaurus rex, is shown on display at the Field Museum in Chicago, Illinois in this May 17, 2000 file photo
The dinosaur named "Sue," a 41-foot-long Tyrannosaurus rex, is shown on display at the Field Museum in Chicago, Illinois in this May 17, 2000 file photo. The 67 million-year-old dinosaur discovered near Faith, South Dakota, was named for Susan Hendrickson, who unearthed the giant creature. The hot question of whether dinosaurs were warm-blooded like birds and mammals or cold blooded like reptiles, fish and amphibians finally has a good answer. Dinosaurs, for eons Earth's dominant land animals until being wiped out by an asteroid 65 million years ago, were in fact somewhere in between. REUTERS

Dinosaurs performed a bird-like dance, clawing huge troughs in the ground with their feet to attract mates 100 million years ago, according to a new study. Palaeontologists who have studied these marks, left behind on the ground in western Colorado, say that the findings apparently confirm speculations that theropods have engaged into courtship rituals.

Lead scientist Martin Lockley, a professor of geology with the University of Colorado Denver, said experts already know that Tyrannosaurus rex was a visual animal, showing off feathers, crests and good vision. However, there has not been any physical evidence that these dinosaurs’ anatomy and behaviours were designed for energetic display.

The study, published online in the journal Scientific Reports on Jan 7, reports of the 50 scrape marks found in a sandstone, echoing the traces that birds leave behind after competing for potential mates. These are also known as nest scrape display or scrape ceremonies.

Lockley said in a press release that these are the first sites with evidence of dinosaur mating display rituals discovered and the first physical evidence of courtship behaviour, filling in the missing gap in the understanding of dinosaur behaviour. The scrapes, measuring up to six feet long, were found in Dominguez-Escalante and Gunnison Gorge conservation areas.

The scientists say this new fossil evidence supports the theory that sexual selection is one of the main drivers of evolution, where males compete with each other to garner the attention of females. Similar behaviour can be observed in mammals and birds.

The team noticed that removing the scrape marks from giant rocks was impossible without inflicting damages on it. Hence, they produced 3-D images of these scrapes with a photo-layering technique called photogrammetry. Rubber mould and fibreglass copies of the scrapes were also made, which were stored at the Denver Museum of Nature & Science.

"The scrape evidence has significant implications," Lockley added. "This is physical evidence of pre-historic foreplay that is very similar to birds today. Modern birds using scrape ceremony courtship usually do so near their final nesting sites. So the fossil scrape evidence offers a tantalizing clue that dinosaurs in 'heat' may have gathered here millions of years ago to breed and then nest nearby."