Dinosaurs - Cretaceous Gallery

144-65 million years ago

Spanning 144 to 65 million years ago, the Cretaceous covers 75 million years. For the first 30 million of those years, we know very little about dinosaur life in the Ancient Southwest as there is very little rock exposed from that era. While there were fewer kinds of dinosaurs in the Cretaceous overall, there were larger populations of the dinosaurs that did thrive in this period. Late Cretaceous dinosaur bones have been discovered in the Southwest right up to the end of the Age of the Dinosaurs.

Tyrannosaurus Rex

This 'tyrant lizard' is one of the most infamous in dinosaur legend - he was a huge meat-eating creature with unforgiving teeth in a massive head, with powerful legs equipped for a chase, and the height to see well into the distance to locate prey. As a theropod, T Rex walked on two hind legs, but to balance the mass of his head and tail, may have run in a horizontal position with head forwards, tailed stretched out behind. But T Rex did not dominate the Age of the Dinosaurs, in fact he didn't even exist until the last 4-5 million of the Cretaceous period. Weighing in at up to 5 tons, this huge fellow could be 45 feet long and stand nearly 20 feet tall. His head alone was four feet long, the jaws making up three feet of that, with 6-inch saber-like teeth. And then on the other end, his toes were eight inch talon like claws, three pointing forwards, one to the back, helping support this beast as he stood tall to survey his landscape, and then to help balance him as he ran after his prey. But with his tiny arms, it is doubtful he caught meals with his hands - more likely he chomped them with his three-foot jaws … or, some scientists suggest maybe he wasn't a killer, but a scavenger. That theory is based on the fact that his eyes were relatively small, his hands nearly useless, and his olfactory (smell) capability was great - like a vulture.

T Rex are known to have lived in the northern western area, not in the heart of the Southwest … but, a find in Baja California suggests one of his close relatives also roamed the southern section of the Southwest.

Alamosaurus

Alamosaurus is one of only two Sauropods (the huge, four legged plant eaters) to live in North America during the Late Cretaceous. She is named after a rock formation in New Mexico called Ojo Alamo, where she was discovered. Compared to other sauropods she was not huge, but at 50 feet from nose to tail, she was one of the biggest creatures in her own landscape. This dinosaur roamed the Late Cretaceous tropical forests, munching foliage from high up in the forest canopy with her long graceful neck. Her front legs were shorter than her hind legs, so she walked like an Apatosaurus (Jurassic) leaning forwards with higher hips. A whole skeleton fossil has not yet been found, but elements have been discovered in New Mexico, Utah and Texas.

Hadrosaurs

Here is a dinosaur with an unusual flat, rounded, horned bill that has been found in New Mexico, Baja California, Mexico and up into Canada. It was the most abundant type of dinosaur in the Late Cretaceous in North America, and its fossils make up 75% of all North American fossils that have been found. All had rounded bill-like mouths; some also had exotic crests on their heads (like the Lambeosaurus found in Baja California). One's horn-like crest even arched back from the forehead to towards the middle of the back. This one was the Parasaurolophus and was found in New Mexico. Some of these crests were solid, others had nasal passages for breathing through. What so you think these crests or horns were for? Improving their sense of smell? Allowing them to make distinctive nasal sounds? To help identify their own kind from other crested types? To do battle with? To breathe while eating?

The Hadrosaurs did not have claws on the their hind feet, they had toes that ended in a hoof. And their front hands were webbed. They grazed on plants through out the day. While not having front teeth, they could have up to 200 rear teeth that ground the plant foods they had snapped off with their beak. They raised their young from eggs as hatchlings, and the young did not develop crests until they were in young adulthood. Of the 16 types of Hadrosaurs found in North America, 10 types had hard or no crests, and 6 had hollow crests.

California Dinosaurs
One of the most important dinosaur discoveries in recent years took place in Northern California in 1991 where it had been thought no dinosaurs had existed as much of the western sates had been completely under water during the Mesozoic. Camp Internet's Trail Guide, Professor Richard Hilton is a geologist who was out hunting for ammonite fossils in the foothills of the Cascade Mountains, a little west of Mount Shasta. He found some unusual bone specimens and brought them back to store in the lab. A few years later, his department at Sierra College hired a paleontologist from Utah, Frank De Courten, who immediately recognized the importance of the find. What they had discovered in 1993 was that 115 million years ago a swift footed, deer sized - Hypsilophodont - dinosaur, walking on it back legs, roamed the heavily forested northern mountains of what is now California. He had short little front arms and hands that were dexterous enough to gather plant food (he was a plant eater). This find proved that there had been more dinosaur life in the west than previously imagined.