Nothronychus

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Nothronychus
Artistic reconstruction of Nothronychus mckinleyi

Artistic reconstruction of Nothronychus mckinleyi

Temporal occurrence
Upper Cretaceous (Lower to Middle Turonium )
93.9 to 91.4 million years
Locations
Systematics
Lizard dinosaur (Saurischia)
Theropoda
Coelurosauria
Maniraptora
Therizinosauridae
Nothronychus
Scientific name
Nothronychus
Kirkland & Wolfe , 2001
species
  • N. mckinleyi Kirkland & Wolfe, 2001
  • N. graffami Zanno et al., 2009
Approximate size comparison to a human today

Nothronychus is a dinosaur - genus from the group of Therizinosauria . The species N. mckinleyi was described in 2001 by James Kirkland and Douglas G. Wolfe after discoveries in the Zuni Basin on the border between New Mexico and Arizona .

These finds come from rocks that belong to the "Morono Hill Formation ", which are dated to the early Upper Cretaceous (Middle Turonian ). A second specimen, described as N. graffami in 2009 , was found in the Tropic Shale Formation in Utah , which is dated to the early Turonian, between half a million and a million years before N. mckinleyi .

The name Nothronychus means something like "lazy claw".

description

Nothronychus is one of the Coelurosauria , the theropod group of carnivores, to which the well-known Tyrannosaurus also belongs. However, Nothronychus is assigned to the subgroup of the Maniraptora . These theropods evolved into omnivores, and in the case of Nothronychus and his family even herbivores. He walked more erect on his two legs than his carnivorous ancestors. N. graffami weighed around a ton, was 4.5 to 6 m long and 3 to 3.6 m high. N. mckinleyi was only a little smaller.

A reconstruction of 40 to 50% of his skeleton, from two different species, allowed the scientists to describe his leaf-shaped teeth with round roots, a long neck, long arms with dexterous hands and 10 cm long, curved claws on the fingers, a large, thick belly, stocky hind legs and a relatively short tail. N. mckinleyi differed from N. graffami in that it was less robustly built, as well as in some details of the vertebrae and a more strongly curved forearm bone ( ulna )

Discovery and Species

The first fossil that was later assigned to Nothronychus was discovered by a team of paleontologists in the Zuni Basin in New Mexico . An ilium (hip bone) of a therizinosaur was initially mistakenly identified as part of a newly discovered ceratopsia , the Zuniceratops . On closer inspection, however, the true nature of the bone emerged, and soon other bones were found. The New Mexico team, led by paleontologists Jim Kirkland and Doug Wolfe, published this find on August 22, 2001 in the Journal of Vertebrate Paleontology as the species Nothronychus mckinleyi . However, this name was already published on June 19, 2001 in a column by RE Molnar in the Arizona Republic newspaper.

A second, fully preserved therizinosaur was found in 2000 by Merle Graffam, a resident of Big Water, Arizona, in the Tropical Shale Formation of Utah . The area around Big Water was the destination of several expeditions by teams from the Museum of Northern Arizona , as it was known for its abundance of marine fossils, particularly plesiosaurs . In the late Cretaceous this region was a shallow sea, the Western Interior Seaway , of which numerous marine deposits have been preserved. The first Graffam find (a large toe bone found in isolation) surprised the scientists because it was clear that it was part of a land-based dinosaur, not a plesiosaur. However, the site must have been around 100 kilometers from the Cretaceous coastline. An excavation by a team at the Museum of Northern Arizona (MNA) discovered additional skeletal parts that the researchers used to determine that it was a therizinosaur. This was the first specimen of this group of dinosaurs to be found on the American continent. All therizinosaur fossils so far came from Mongolia and China .

The specimen found in Utah and examined by the MNA team was found to be a close relative of N. mckinleyi , although it has a stronger structure and is about half a million years older . This older specimen was first mentioned publicly in 2002 in two discussions at the 54th meeting of the Rocky Mountain Geological Society of America. Subsequently, it was named in an issue of the online magazine Arizona Geology as a species different from N. mckinleyi , but not named. The species was named and classified as the new species Nothronychus graffami on July 15, 2009 by Lindsay Zanno and her colleagues in the journal Proceedings of the Royal Society B with reference to the discoverer Merle Graffam . A reconstructed N. graffami skeleton has been on display at the Museum of Northern Arizona since September 2007.

literature

Web links

Commons : Nothronychus  - collection of images, videos and audio files

Individual evidence

  1. ^ Gregory S. Paul: The Princeton Field Guide To Dinosaurs. 2010, pp. 158-159 online
  2. ^ A b c Lindsay E. Zanno, David D. Gillette, L. Barry Albright, Alan L. Titus: A new North American therizinosaurid and the role of herbivory in 'predatory' dinosaur evolution. In: Proceedings of the Royal Society. Series B: Biological Sciences. Vol. 276, No. 1672, 2009, ISSN  0950-1193 , pp. 3505-3511, doi : 10.1098 / rspb.2009.1029 .
  3. ↑ a b c d David D. Gillette: Therizinosaur - Mystery of the Sickle-Clawed Dinosaur (= Arizona Geology. Vol. 37, No. 2, 2007, ZDB -ID 2140610-8 ). Arizona Geological Survey, Tucson AZ 2007, digitized version (PDF; 8.86 MB) .
  4. ^ A b James I. Kirkland , Douglas G. Wolfe: First definitive therizinosaurid (Dinosauria; Theropoda) from North America. In: Journal of Vertebrate Paleontology. Vol. 21, No. 3, 2001, ISSN  0272-4634 , pp. 410-414, doi : 10.1671 / 0272-4634 (2001) 021 [0410: FDTDTF] 2.0.CO; 2 .
  5. ↑ L. Barry Albright III, David D. Gillette, Alan L. Titus: New records of vertebrates from the Late Cretaceous Tropic Shale of Southern Utah. In: Paleontological Research in Grand-Staircase Escalante National Monument and Surrounding Area I. 2002, (abstract) .
  6. ↑ David D. Gillette, L. Barry Albright III, Alan L. Titus, Merle H. Graffam: Discovery and excavation of a therizinosaurid dinosaur from the Upper Cretaceous Tropic Shale (Early Turnoian), Kane County, Utah. In: Paleontological Research in Grand-Staircase Escalante National Monument and Surrounding Area I. 2002. (abstract) .