Rex run: Watch Tyrannosaurus rex run on horse track

WATCH: Running of the Rexes

AUBURN, Wash. — A group of Tyrannosaurus rexes had their day at the races, trying to find out who really was the king of the dinosaurs.

The race first appeared like any other event at Emerald Downs, but as soon as the gates popped open, adults and kids alike saw the traditional equines weren't around. Instead, T. rexes came out running.

The race is held by TriGuard, a pest control company, NPR reported.

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More than 30 employees of the company donned the costumes for the annual race held over the weekend, USA Today reported.

This was the third year for the Running of the Rexes and it has become so popular that non-employees have called the company asking to enter, USA Today reported.

But the race itself evolved into the Dino Run. One year, it was themed to Hawaiian clothing, then togas. But the Rex Run stuck after the first dinosaur dash in 2017, according to NPR.

Whichever rex does survive to cross the finish line first, doesn't actually win a prize other than bragging rights for the year, NPR reported.