Body length
InferredAbout 5.3 m (educational genus reference)
The museum does not identify one measured individual or growth stage; this is not a species maximum. [D2]
EXHIBIT 214
Nothronychus
Nothronychus mckinleyi and N. graffami
Dinosaur
Nothronychus was a therizinosaur with a small head, long neck, broad abdomen and impressive hand claws. [3]
TWO WAYS TO PICTURE THE PAST
Science & the silver screen
Compare the evidence with the familiar movie image. The illustrations are not to a shared scale.
01 / SOURCE-INFORMED RECONSTRUCTION
A life reconstruction from the evidence
Image unavailableIllustrative life reconstruction of Nothronychus in a period-appropriate environment; coloration and missing anatomy are interpretations.The exhibit and its credited image source remain available.
An illustrative reconstruction. Compare its anatomy with the evidence and limitations in the dossier. [3]
Source-informed reconstruction. Appearance evidence [3]. Original illustration; missing anatomy, coloration and scenery include interpretation.
Fossils constrain this life reconstruction. Missing anatomy, coloration and the environmental scene include interpretation; the dossier explains the evidence limits.
02 / MOVIE-STYLE INTERPRETATION
A cinematic imagination
Image unavailableIllustrative reconstruction of Nothronychus mckinleyi and N. graffami; missing anatomy, pose and colors are hypotheses.The exhibit and its credited image source remain available.
An illustrative reconstruction. Compare its anatomy with the evidence and limitations in the dossier. Lighting, coloration and scenery are artistic choices. This image does not document a fossil locality or behavior.
Original artwork · artistic interpretation.
Scientific view: source-informed reconstruction, credited paleoart or specimen-based imagery. Movie-style view: Original artistic interpretation. Reconstructions involve uncertainty.
PERIODLate Cretaceous[1]
DIETHerbivoreEvidence and uncertainty in the dossier
TOTAL LENGTHSee the dossierEstimate scope matters
FOSSILS FOUNDUnited States[1]
MEET THE ANIMAL
Meet Nothronychus
Nothronychus belonged to the therizinosaurs, an unusual branch of the two-legged theropod dinosaurs. Its long neck, small head and roomy belly made it look very different from a large meat-eating hunter. The Natural History Museum of Utah interprets this body plan as suited to plant feeding. Its unusually large, curved hand claws are striking, but their appearance alone does not reveal every activity they performed. The Utah specimen reached a sea after death, although its anatomy belonged to a land animal. [D3]
Two species have separate skeletons. Burial pressure altered some bone shapes; the Utah body lacks a skull. [D1]
Scientists can investigate movement even when muscles and ligaments are missing. A recent study reconstructed hip ligaments using marks on the bones and comparisons with other animals. Its model suggests a wide-legged, slower-moving dinosaur whose knees supplied much of its leg motion. That is a tested anatomical hypothesis, rather than a film of a walking animal or a measurement of its running speed. [D4]
PREHISTORIC ANIMAL DOSSIER
A life in profile.
The animal, the evidence, and the questions still open.
Partial skull and body bones help reconstruct this unusual theropod. Hip-ligament research proposes a slow, wide-legged gait rather than measuring an actual walking animal. [D2] [D4]
Profile scope: Genus — Nothronychus; two species represented by separate partial skeletons. [D1]
- Time
- Late Cretaceous
- Fossil locations in this exhibit
- United States
How to read the evidence
Source supported identifies a description documented by the cited source. Inferred marks a reconstruction or functional estimate. Debated marks competing interpretations. Not established means the sources reviewed for this dossier do not support a firm conclusion; it does not mean a behavior never occurred.
A size reference is an estimate, not a population range. Nesting evidence does not by itself establish courtship, mate choice, or lifelong pairing.
Body mass
Not establishedNot established here
The inspected sources provide no comparable, maturity-qualified body-mass estimate adopted here. [D2]
Diet and feeding
InferredPlant feeding inferred
Small head and capacious gut support herbivory; a museum also labels the genus omnivorous. No particular meal is established. [D3] [D2]
Habitat and setting
InferredTerrestrial western North America
The Utah carcass reached an offshore sea; marine Tropic Shale burial does not show an aquatic lifestyle. [D3]
Movement
InferredBipedal, broad-gauge gait proposed
A ligament model suggests restricted hip motion and slower progression. It does not provide an observed gait or measured speed. [D4]
Recognizable anatomy
Source supportedLong neck and large claws
The Utah museum emphasizes a small head and broad gut in its plant-feeding reconstruction. [D3]
Reproduction & life together
Reproduction and nesting
Not establishedNot established here
Focused searches and reviewed osteology found no assigned eggs, nests or parental-care evidence. [D1]
Mating and courtship
Not establishedNot established here
The reviewed museum directory supplies no taxon-specific mating, courtship or sex-color evidence. [D2]
Social behavior
Not establishedNot established here
Transported bones do not demonstrate a living herd. [D1]
Dossier research & sources
Sources and inspection notes for the claims in this profile.
- The Slothful Claw: Osteology and Taphonomy of Nothronychus mckinleyi and N. graffami (Hedrick et al., 2015)PLOS ONE 10(6):e0129449 · Accessed 2026-10-05Full original osteology, species diagnoses, specimens and taphonomy inspected. N. mckinleyi MSM P2117 comes from the middle Turonian Moreno Hill Formation of New Mexico; N. graffami UMNH VP16420 comes from early Turonian Tropic Shale in Utah. The latter lacks a skull and was transported offshore. Differences in ulnar curvature can reflect burial compression; mixed, transported bone accumulations do not establish social behavior. · Inspected: page
- Nothronychus dinosaur directoryNatural History Museum, London · Accessed 2026-10-05Institutional directory inspected: 5.3 m is an educational genus reference without fossil-individual or maturity scope. Its omnivorous label differs from the plant-feeding anatomical interpretation in the Utah museum profile; neither identifies a preserved meal. · Inspected: page
- Kane County — Nothronychus graffamiNatural History Museum of Utah · Accessed 2026-10-05Full institutional account inspected: small head, long neck, wide gut and large hand claws support herbivory; the land animal was washed into a marine setting. The 14-foot reference applies to the displayed N. graffami reconstruction and is not pooled with the London genus reference. · Inspected: page
- Reconstruction of soft noncontractile tissue in the derived therizinosaur Nothronychus (Smith and Gillette, 2023)Journal of Morphology 284(5):e21579 · Accessed 2026-10-05Original indexed abstract inspected. Hip-ligament reconstruction from fossil scars and comparative anatomy proposes restricted femoral motion, laterally abducted femur and slow broad-gauge progression. This is a functional model, not a Nothronychus trackway or measured speed. · Inspected: abstract
THE STORY IN THE FOSSILS
Evidence behind Nothronychus
The best-known Utah skeleton came from rocks laid down at sea. Its bones nevertheless belong to a land-dwelling dinosaur. [3]
Reconstructing motion also means restoring missing soft tissues. The proposed hip ligaments constrain a possible gait without preserving actual footsteps. [4]
A note on scale and time
The dossier identifies the scope of each reference estimate. A mount, an individual fossil and a species-wide adult range are different measurements. Comparison metrics remain unavailable where adult scope has not been established. Unknown does not mean zero.
Sources & editorial notes
Sources support the stated claims and scopes. Refer to the evidence notes for uncertainty.
- The Slothful Claw: Osteology and Taphonomy of Nothronychus mckinleyi and N. graffami (Hedrick et al., 2015)PLOS ONE 10(6):e0129449 · Accessed 2026-10-05Full original osteology, species diagnoses, specimens and taphonomy inspected. N. mckinleyi MSM P2117 comes from the middle Turonian Moreno Hill Formation of New Mexico; N. graffami UMNH VP16420 comes from early Turonian Tropic Shale in Utah. The latter lacks a skull and was transported offshore. Differences in ulnar curvature can reflect burial compression; mixed, transported bone accumulations do not establish social behavior. · Inspected: page
- Nothronychus dinosaur directoryNatural History Museum, London · Accessed 2026-10-05Institutional directory inspected: 5.3 m is an educational genus reference without fossil-individual or maturity scope. Its omnivorous label differs from the plant-feeding anatomical interpretation in the Utah museum profile; neither identifies a preserved meal. · Inspected: page
- Kane County — Nothronychus graffamiNatural History Museum of Utah · Accessed 2026-10-05Full institutional account inspected: small head, long neck, wide gut and large hand claws support herbivory; the land animal was washed into a marine setting. The 14-foot reference applies to the displayed N. graffami reconstruction and is not pooled with the London genus reference. · Inspected: page
- Reconstruction of soft noncontractile tissue in the derived therizinosaur Nothronychus (Smith and Gillette, 2023)Journal of Morphology 284(5):e21579 · Accessed 2026-10-05Original indexed abstract inspected. Hip-ligament reconstruction from fossil scars and comparative anatomy proposes restricted femoral motion, laterally abducted femur and slow broad-gauge progression. This is a functional model, not a Nothronychus trackway or measured speed. · Inspected: abstract
KEEP EXPLORING
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