02-10-2008 - Biodiversity

sagar: Author=’Lindsay Patterson’ program=’5397′ video=”Compare the skulls of these three dinosaurs: The same, or different? Dracorex pictured on top left, Stygimoloch on top right, and Pachycephalosaurus on bottom. Image credit: Holly N. WoodwardNew evidence suggests that what was thought to be three separate dinosaur species might actually be the same dinosaur – in three different stages of growth.

Jack Horner is a paleontologist at Montana State University who’s interested in dinosaur evolution and ecology. At the 2007 meeting of the Society of Vertebrate Paleontology, Horner told his colleagues that two juvenile specimens of the dinosaur Pachycephalosaurus were victims of mistaken identity.

Pachycephalosaurus has a distinctive dome shaped head that’s made of bone. Paleontologists had identified two smaller but related species – Stygimoloch and Dracorex Hogwartsia – named after the Harry Potter novels. Physically, these dinosaurs all look different.

So how can Horner tell that they’re all the same dinosaur? By a simple comparison.

He took CT scans and cut open the skulls of the different specimens. He found that the two smaller dinosaurs have the spongy, light bone typical of juvenile dinosaurs – which would have grown into the massive, heavy boned dome of the Pachycephalosaurus. Horner said that if you compare it to the way that human babies grow into adults, it’s easy to see how these two smaller dinosaurs developed into pachycephalosaurs.

Dracorex was the smallest dinosaur species identified. It didn’t have a dome, but it had big spikes sticking out from the back of its head. Stygimoloch was medium sized, with a small dome and spikes. Pachycephalosaurus was full grown, with a large dome and bumps in the place of spikes.

An adult pachycephalosaur was 12 to 15 feet long, and walked on its hind legs. It lived about 68 to 65 million years ago, alongside the T. Rex and Triceratops, making it among the last of the dinosaurs to live on Earth.

Jack Horner previously worked with pachycephalosaurs to disprove the notion that they used their boned domes to butt heads with each other. He told Earth & Sky that they would need a cushion in their heads to protect their brains, like big-horned sheep. Horner said that if Pachycephalosaurus did indeed butt heads, it would only last for one fight.

Written by Lindsay Patterson

3 Responses to “Private: Dinos suffer case of mistaken identity”

1. poohead32 says:

   February 11, 2008 at 7:06 pm

   Sweet!!! i didnt know that!!!!

   Reply
2. joseph aaron aguilar says:

   February 13, 2008 at 9:15 pm

   that was interesting!

   Reply
3. redentor marquez 3 says:

   February 26, 2008 at 8:54 am

   Yes! Certainly I see the resemblance!

   Reply