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.

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


Hedrick, B., Zanno, L., Wolfe, D., Dodson, P. 2015. The slothful claw: Osteology and taphonomy of Nothronychus mckinleyi and N. graffami (Dinosauria: Theropoda) and anatomical considerations for derived therizinosaurids. PLOS ONE. doi: 10.1371/journal.pone.0129449

Previous Paleo Profiles:

Atychodracon megacephalus
Sefapanosaurus zastronensis
Huanansaurus ganzhouensis
Zhenyuanlong suni
Lepidus praecisio

3 thoughts on “Paleo Profile: Nothronychus graffami

  1. We actually had more that this image suggests, Braincase, much of neck, almost entire forelimb (minus claws), both ischia (lower rear pelvic bones) caudal vertebrae and some leg bones including claws. The Zuni Basin beast was better preserved (not flattened), And can be dated to the basal Collignoniceras woolgari woolgari ammonite subzone near the base of the middle Turonian, while N. graffmani is from near the boundary of the Vascoceras birchbyi and Mammites nodosoides ammonite Zones in the middle of the Lower Turonian. There is certainly less than one half of one million years between them. Remember my dissertation was on theoretical biostratigraphy of this same stratigraphic interval and the geological timescale for this interval was based on volcanic ashes I collected.

    One of the paleontologists we were working with in the field pushed hard that we make the then unidentified ischium of Nothronychus the holotype of Zuniceratops as it was so weird. Nothronychus mckinleyi was found in a bone bed of Zuniceratops. Fortunately I insisted that we continue to make the type of Zuniceratops a scrappy associated skeleton from across the valley. Thus, the world was saved from the embarrassing therizinosaurs Zuniceratops christopheri and Z. graffmani.

    Oh and Ian; I came up with the name Nothronychus, as in means “sloth claw” for that very reason.

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