Nothronychus ‭(‬slothful claw‭)‬

Short Info

Nothronychus ‭(‬slothful claw‭)‬

Phonetic : Nof-ron-e-kus.

Named By : J.‭ ‬I.‭ ‬Kirkland‭ & ‬D.‭ ‬G.‭ ‬Wolfe‭ ‬-‭ ‬2001

Diet : Herbivore

Size : Estimated 4.5 – 6 meters long

Type of Dinosaur : Large Theropod

Type Species : N.‭ ‬mckinleyi‭ (‬type‭)‬,‭ ‬N.‭ ‬graffami

Found in : USA,‭ ‬New Mexico‭ ‬-‭ ‬Moreno Hill Formation,‭ ‬and Utah‭ ‬-‭ ‬Tropic Shale Formation

When it Lived : Late Cretaceous, 94-89 million years ago

Nothronychus, which means “slothful claw”, is a genus that includes therizinosaurids theropod dinosaurs. It was found in North America during Late Cretaceous. Douglas G. Wolfe and James Kirkland described the type species Nothronychus mckinleyi in 2001. It was found near New Mexico’s border to Arizona in an area called the Zuni Basin. The rocks that make up the Moreno Hill Formation date to the late Cretaceous period (mid–Turonian stage), which occurred around 91 million year ago. The second specimen, Nothronychus graffami (described as a second species in 2009), was discovered in the Tropic Shale in Utah. It dates to the early Turonian and is approximately one million and a quarter million years older than N. mckinleyi.


Nothronychus (1)Kabacchi, CC BY 2.0, via Wikimedia Commons


Nothronychus were large herbivorous, bulky theropods that ate large quantities of herbivorous theropods. They had a sloth-like hip similar to the one of non-related ornithischians, four-toed feet with all the four toes facing forward, long necks, and prominent clawed arms. They were approximately 4.2m (14.1ft) long and weighed 800kg (1,800 lb). N. graffami was slightly stronger than N. mckinleyi.

A team of paleontologists discovered the first fossil evidence that Nothronychus had. They were working at the Haystack Butte site in New Mexico. Therizinosaur hip bone (a therizinosaurischium) was initially mistaken for a Squamosal, which is a part the skull crest of the recently discovered Ceratopsian Zuniceratops. However, closer inspection revealed the true identity and more pieces of the skeleton were soon discovered. Their find was published in the Journal of Vertebrate Paleontology by the New Mexico team led paleontologists Jim Kirkland, and Doug Wolfe on 22 August 2001. It is the first specimen of the new species Nothronychus McKinleyi. However, the Arizona Republic newspaper was the first to publish the name in a column written by R.E. Molnar. Nothronychus is the generic name. It comes from Nothros (nothros meaning slothful, and onux (onyx meaning claw) in Greek. Bobby McKinley, the rancher on whom the fossil discoveries were made, was given the specific name mckinleyi. The specimen MSM P2106, the holotype, is composed of very few skull fragments, a braincase and parts of the shouldergirdle, pelvis, hindlimbs, and forelimbs.

Merle Graffam (a Big Water resident) discovered UMNH VP 16420 from the Tropic Shale Formation in southern Utah. This second, more complete specimen dates back to the early Turonian stages. Many expeditions were made to Big Water by the Museum of Northern Arizona (MNA) teams. The area was well-known for its abundance of marine reptile fossils and plesiosaurs. The area was submerged in the Western Interior Seaway during the late Cretaceous. It also retains large marine deposits. Graffam’s first discovery, a large, isolated toebone, was a surprise to his colleagues. It clearly belonged to an earth-dwelling dinosaur and not a Plesiosaur. The bone was located close to the Cretaceous shoreline at the time. MNA crew excavated the area and discovered more of the skeleton. Scientists determined that the bone was a therizinosaur and the first such example to be found in the Americas. Therizinosaur fossils have been sourced from China and Mongolia. N. graffami, which is the more complete of the two species, does not have the skull.

Although closely related to N. mckinleyi’s Utah specimen, the MNA team found that it was heavier and half a million years younger. MNA’s specimen was announced for the first time at the 54th Rocky Mountain Geological Society of America meeting in 2002. Later, it was discussed in Arizona Geology as a distinct species of N. mckinleyi. However, it was not named. Lindsay Zanno and his colleagues named the specimen Nothronychus graffami in the journal Proceedings of the Royal Society B, 15 July 2009. Graffam was the one who discovered the original specimens. N. graffami is named after Graffam. In September 2007, a reconstructed skeleton from N. graffami was displayed at the MNA. Hedrick and his colleagues completed a large osteological review of both species and respective specimens in 2015 and concluded that Nothronychus is one of the most well-known and complete therizinosaurids.

Source: Wikipedia