Analysis of a new species of extinct reptile whose remains were collected near Big Spring, Texas in 1940 has shown that the shapes of the body and skull of the most iconic dinosaurs are not completely original.
In a new study published in the Current Biology on Sept. 22, a group of paleontologists performed a detailed CT scan of the remains of a new species of extinct reptile called Triopticus primus, or the "First of Three Eyes" that lived about 230 million years ago before the era of the dinosaurs.
The creature was characterized by a large natural pit at the top of its head that looked like an extra eye. It also featured a very thick skull roof similar to those of the distantly related pachycephalosaur dinosaurs that emerged more than 100 million years later.
Many of the other extinct animals that were found with Triopticus in the Otis Chalk fauna were also found to have body parts that resembled those of dinosaurs. Among these features are those that were similar to the toothless beaks of ornithomimids, the long snouts of the Spinosaurus and the armor plates of the ankylosaurus.
The Triopticus provides an example of evolutionary convergence, a common evolutionary phenomenon that occurs when two distantly related species independently evolve similar body shape and appearance likely as a result of having to adapt to similar environments.
"We introduce a new Triassic stem archosaur that is unexpectedly and remarkably convergent with the 'dome-headed' pachycephalosaur dinosaurs that lived over 100 million years later," the researchers wrote in their study.
"Surprisingly, numerous additional taxa in the same assemblage (the Otis Chalk assemblage from the Dockum Group of Texas) demonstrate the early acquisition of morphological novelties that were later convergently evolved by post-Triassic dinosaurs."
The latest finding offered evidence of convergence across a considerable length of time and among a diverse group of dinosaurs and reptiles from the Triassic and Jurassic periods.
The Triopticus in particular exemplifies body-shape convergence as the shape of its skull appear to have been copied by distantly related dome-headed dinosaurs that emerged after more than 100 million years.
"It is amazing to think that many of the iconic dinosaur features that we know and love, such as long snouts, toothless beaks, armor plates and thickened dome skulls, were arrived at completely independently up to 100 million years earlier in these distant reptilian cousins," said University of Chicago evolutionary biologist Katharine Criswell.
