Nothronychus looks over the Past Worlds gallery of the Natural History Museum of Utah.
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Photo by Brian Switek.
Nothronychus looks over the Past Worlds gallery of the Natural History Museum of Utah.

Paleo Profile: Nothronychus graffami

Name: Nothronychus graffami

Meaning: The genus name translates to “slothful claw”, while the species name honors the dinosaur’s discoverer, Merle Graffam.

Age: Around 93 million years ago

Where in the world?: Southern Utah

What sort of critter?: Nothronychus was an herbivorous theropod dinosaur that belonged to a lineage called therizinosaurs.

Size: Over 15 feet long.

How much of the creature’s body is known?: Vertebrae from the neck, back, and tail; ribs; hips; hindlimb, and forelimb.

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Blue bones are those known for Nothronychus mckinleyi, red are for N. graffami, and purple bones represent elements known in both. From Hedrick et al., 2015.

Claim to fame: In 2001, paleontologists Jim Kirkland and Doug Wolfe named a very strange dinosaur. Relatively little of its skeleton was known – a few vertebrae, part of an arm, part of a leg, and a piece of hip bone found in northern New Mexico – but it was enough to identify the animal as one of the tubby, fuzzy, long-necked, large-clawed herbivores called therizinosaurs. They named the species Nothronychus mckinleyi.

But even as the first Nothronychus was heading to press, a second one had been uncovered. Merle Graffam found a more complete skeleton in slightly older rocks of southern Utah. No one had expected to find a dinosaur in the rocks Graffam was searching. The sediment was from an ancient seaway that yielded plesiosaurs and other marine reptiles. But the anatomy didn’t lie. In 2009, Lindsay Zanno named the dinosaur as a second species of NothronychusN. graffami – that had been washed out to sea and buried far from shore.

The second skeleton provided paleontologists with a far more detailed view of Nothronychus than the first. But did the two bodies really belong to different species? University of Pennsylvania paleontologist Brandon Hedrick had another look earlier this year, and, indeed, the two can be distinguished from each other as distinct species. More than that, they were separated in space by two hundred miles and anywhere between 1.5 and 3 million years. Perhaps, by searching in that window, paleontologists will be able to uncover how this bizarre dinosaur evolved along the edges of North America’s long lost sea.


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