(Pronunciation: uh-BUY-dough-SORE-us MAC-in-TOSH-eye)
Age: Early Cretaceous (~105 million years ago)
Where It's Found in Utah: Dinosaur National Monument, Uintah County.
Geologic Formation: Cedar Mountain Formation (Ruby Ranch or Mussentuchit Member)
Classification: Saurischia - Sauropodomorpha – Sauropoda – Macronaria - Titanosauriformes
Description: At 43 feet (13 meters) long, Abydosaurus was a moderately-sized sauropod dinosaur, a little smaller than Camarasaurus. It had a high, boxy skull with a protruding snout – perfect for cropping vegetation from the tops of trees. Abydosaurus belongs to the same sauropod group as Camarasaurus, but it is most closely related to another Late Jurassic dinosaur from the Morrison Formation that you might have heard of – Brachiosaurus. Although their skulls and neck bones are very similar, Abydosaurus had narrower teeth than Brachiosaurus. This allowed it to pack more teeth in its mouth and replace them at a faster rate as they wore out. Like all dinosaurs and other reptiles, Abydosaurus replaced its teeth many times throughout its life.
Why It’s a Top NHMU Dinosaur: Abydosaurus is one of the newest dinosaurs discovered in Utah! It was discovered just 1200 feet away from the famous Late Jurassic Carnegie Quarry in the Morrison Formation at Dinosaur National Monument. How could these two fossil sites be so close together yet be separated by 45 million years of time? It turns out that rock layers at Dinosaur National Monument are tipped on edge by geologic forces so that they are oriented almost vertically. Think about a book– each rock layer is a page that’s laying face down on the table. These rock layers are stacked up through time like the pages in a book, with the youngest rock layers on top. Then geologic forces contort the rock layers so that the book is vertical, and you see the edge of the pages instead of the faces. So older fossils buried beneath younger ones can end up almost side-by-side.
Chure, D., B. B. Britt, J. A. Whitlock, and J. A. Wilson. 2010. First complete sauropod dinosaur skull from the Cretaceous of the Americas and the evolution of sauropod dentition. Naturwissenschaften 97:379-391.
Brigham Young University. Abydosaurus: New dinosaur discovered head-first, for a change.
Image: © Victor Leshyk
Author: Randall Irmis, Curator of Paleontology at the Natural History Museum of Utah (2012)