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Dinosaur or crocodile? An Arizona mystery in bones

December 20 , 2016:

by Ron Dungan

For Petrified Forest paleontologists, finding fossils is just the beginning. Piecing them together yields surprises.

For paleontologist Bill Parker, finding fossils is easy. Putting them together is the hard part.

Parker works at Petrified Forest National Park, a boneyard of prehistoric plants and animals in the high desert of northern Arizona best known for its massive deposits of petrified wood. But the logs are only part of the park’s fossil record.

Parker and his colleagues frequently turn up fossilized bits of reptiles, fish, dinosaurs and other animals. Piecing bone fragments together is a long, detailed process. Sometimes, researchers are not even sure what animal they are working with when the bones come into the lab.

“It’s kind of like a murder mystery, where all the evidence has been left out in the rain and there are no witnesses,” Parker said.

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Imagine the murder victim’s corpse on river bank. The killer, a large dinosaur, has lumbered off into the conifers and ferns to rest. Scavengers find the carcass, rip off an arm or a leg and leave the area. Heavy rains wash the skull downstream. What’s left settles into ground and hardens over time.

The string of events is never the same, but the work of scavengers, weather and other events scatters bones for the ages, so paleontologists rarely find entire skeletons in the field. They visit museums, read academic papers and talk about their work – sometimes one researcher has a skull, another has a neck, a shoulder, an arm. They think about what an animal might have looked like.

“I put fossils together in my sleep,” Parker said.

Sometimes, the pieces fall together in his dreams and he awakes to a eureka moment. The park’s curator, Matt Smith, said he's had the same experience.

For the most part, the work is routine, if painstakingly detailed. But over time, the park has yielded major discoveries – 28 animals new to science with more possibly on the way. Every now and then, researchers find whole skeletons. The finds can help solve mysteries of deep time, in this case, of the Triassic, an age before dinosaurs ruled the planet.
A mystery that started with teeth

The mystery began with a set of teeth, leaf shaped, that appeared to belong to a plant-eating dinosaur. They were discovered by a researcher in New Mexico, who found them near Revuelto Creek. He named the species Revueltosaurus, published a paper and stored the teeth at the New Mexico Museum of Natural History.

“We go with the best evidence we have. It looked like a plant-eating dinosaur from the Jurassic,” Parker said. He read the paper and knew about the animal. A few teeth similar to the ones in New Mexico were later found at Petrified Forest.

In 2004, Parker found some fossilized armor plates in an unexplored hillside in the park. He returned the next day with his boss, who found a jaw. It was May, June, the high desert growing warm.

“We do paleontology in the worst part of the day. The archaeologists think we’re nuts. But we kind of have to because you need overhead light to find the bones,” Parker said.

They kept digging, finding plates and bones, all the time working under the assumption that they were uncovering pieces of two, three, four different kinds of animals.

“We had all these pieces of armor that were all over the hill,” Parker said. They had a Revueltosaurus jaw. They had bits of spine, legs and ankles and rib bones.

“Then we went to the lab and started cleaning it all up and we realized it belonged to one type of animal,” Parker said.

When they were done, they had nine Revueltosaurus specimens, including a couple of skeletons. But something was wrong. The animal didn’t look like a plant-eating dinosaur from the Jurassic.
Plumbing the depths of time

Strip away the Earth’s water and vegetation and its surface would look a lot like the moon, pocked with craters and divots from asteroids and meteorites.

The impacts are one of many ways that the Earth has changed over the years. The geological record tells us of rivers of lava, continents coming together and then splitting, mountains forming, oceans rising and falling.

Scientists believe that these impacts, climate change or a combination of the two may have caused mass extinctions. With each extinction, life on Earth changed.

Large birds once ate small horses, “whales didn’t live in the ocean and snakes had legs,” Parker said. He likes to point out that not all fossils are dinosaurs, and that every living thing has a fossil record – parrots, dogs, cats, crocodiles.

“As you go back they look less and less like what they look like today,” Parker said.

“Most people don’t have any concept of deep time,” Parker said. Children cannot grasp how long ago 215 million years ago really is, and adults generally don’t give it much thought. By the time kids are old enough to understand deep time, they have taken up sports and other pursuits, and they tend to mash dinosaurs, the Ice Age, woolly mammoths and cave men into a compressed timeline.

Parker was like that. As a child he had a brief fascination with dinosaurs, but by 26 he was managing kitchens for a living.

“Started as a dishwasher, worked my way up,” Parker said. Once he got to manager, he wondered: “Is this it?”

About that time his mom bought him a dinosaur calendar, which rekindled that childhood interest. He took classes at Mesa Community College and went on to Northern Arizona University. He worked summer jobs in the Forest Service and had just got engaged during a trip to Havasupai Falls when someone asked if he had heard about an opening at Petrified Forest. He found that he had about two hours to apply before the application period closed, but he made it, and he got the job.



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