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a plant-eating therizinosaurid theropod dinosaur from the Late Cretaceous of North America.
Pronunciation: noh-throh-NI-kus
Meaning: Sloth claws
Author/s: Kirkland and Wolfe (2001)
Synonyms: None known
First Discovery: New Mexico, USA
Chart Position: 405

Nothronychus mckinleyi

Unbeknown to palaeontologists working at New Mexico's Haystack Butte, they had already discovered the first remains of Nothronychus five years before it was named. But they mistook a hip bone (ischium) for a cheek bone (squamosal) and had assigned it to Zuniceratops; the oldest known ceratopsian from North America.

After further discoveries in the same area, Nothyronychus was coined by Kirkland and Wolf and took ownership of said hip bone. Then it trumped Zuniceratops by being the first definitive therizinosaur from outside of Asia and the most complete therizinosaur known from anywhere in the world, and blew minds by sporting a weird suite of features that experts would never have put together had they not found them all rolled into a single skeleton.

Thanks to Nothyronychus we now know that all therizinosaurids had leaf-shaped teeth in a small skull set on a long neck, short, stocky legs with three-toed feet, and three huge hand claws for which they (the "reaping lizards") were named. They're weird on the inside too, with aero-textured vertebrae and a large, tilted, sloth-like pelvis with a backwards-pointing ornthischian-style pubis to accommodate an enormous pot belly. Therizinosaurids were vegetarians yet compared to all other herbivores they had a very short tail. But perhaps the most unusual thing about them is that they were coelurosaurian theropods; the branch of saurischian dinosaurs that are renowned for their fondness of flesh.
(Bobby McKinley's sloth-like claw)Etymology
Nothronychus is derived from the Greek "nothros" (slothful) and "onyx" (claw), named for the large, groundsloth-like claws on its hands. The species epithet, mckinleyi (muh-KIN-lee-ie), honors rancher and research supporter Bobby McKinley, on whose land the specimen was found.
The first remains of Nothronychus were discovered at "Haystack Butte" in the Moreno Hill Formation, Zuni Basin, Catron County, west-central New Mexico, mingled with the remains of Zuniceratops in 1996. However, it wasn't named until further discoveries were made in the same area in 2001. The holotype (MSM P-2117) consists of two skull fragments, a braincase, some vertebrae and parts of the shoulder, forelimbs, pelvis and hindlimbs.
Era: Mesozoic
Epoch: Late Cretaceous
Stage: Turonian
Age range: 94-89 mya
Est. max. length: 5.3 meters
Est. max. hip height: ?
Est. max. weight: 2 tons
Diet: Herbivore
Nothronychus graffami
Nothronychus graffami was named in 2009 by Lyndsey Zanno in honor of Merle Graffam who discovered its first remains—a toe—in the Kaiparowits Basin's Tropic Shale Formation at Kane County, southern Utah, USA, in 2000. The holotype (UMNH VP 16420) is a partial skeleton that was discovered in 2000/2001, but its bones were so badly crushed it took a laboratory full of experts four years to process. Nothronychus graffami differs from Nothronychus mckinleyi in five features of its arm, vertebrae and pelvis, and is of a more robust build and a half million years older. But the weirdest thing is that it was found 100 km from shore at the bottom of what was once the Western Interior Seaway among the remains of plesiosaurs, sea turtles, fish, and sharks.
• Kirkland JI and Wolfe DG (2001) "First definitive therizinosaurid (Dinosauria; Theropoda) from North America". Journal of Vertebrate Paleontology, 21(3): 410-414.
• Clark JM, Maryanska T and Barsbold R (2004) "Therizinosauroidea" in Weishampel, Dodson and Osmólska (eds.) "The Dinosauria: Second Edition". University of California Press.
• Gillette DD (2007) "Therizinosaur: Mystery of the Sickle-Clawed Dinosaur". Arizon Geological Survey: Arizona Geology, Vol. 37, No. 2.
• Holtz TR Jr. (2008) "Dinosaurs: The Most Complete, Up-to-Date Encyclopedia for Dinosaur Lovers of All Ages". (Online supplement here).
• Zanno LE (2010) "A taxonomic and phylogenetic re-evaluation of Therizinosauria (Dinosauria: Maniraptora)". Journal of Systematic Palaeontology Vol.8, Issue 4. doi: 10.1080/14772019.2010.488045
• Lautenschlager S, Rayfield EJ, Altangerel P, Zanno LE, Witmer LM (2012) "The Endocranial Anatomy of Therizinosauria and Its Implications for Sensory and Cognitive Function". PLoS ONE 7(12): e52289.
• Hedrick BP, Zanno LE, Wolfe DG and Dodson P (2015) "The Slothful Claw: Osteology and Taphonomy of N. mckinleyi and N. graffami (Dinosauria: Theropoda) and Anatomical Considerations for Derived Therizinosaurids". PLoS ONE 10(6): e0129449.
• Zanno LE, Gillette DD, Albright LB and Titus AL (2009) "A new North American therizinosaurid and the role of herbivory in ‘predatory’ dinosaur evolution". Proc. R. Soc. B, 276, 3505–3511.
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To cite this page:
Atkinson, L. "NOTHRONYCHUS :: from DinoChecker's dinosaur archive".
›. Web access: 19th Jan 2018.