Body length
InferredApproximately 2–3 m reference length.
Museum educational estimate; not a demonstrated adult range or a measurement of every growth stage. [D4]
EXHIBIT 256
Chilesaurus
Chilesaurus diegosuarezi
Dinosaur
A plant-eating dinosaur with an unusual mixture of skeletal features and an unsettled family-tree position. [4]
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 Chilesaurus 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. [2]
Source-informed reconstruction. Appearance evidence [2]. 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 Chilesaurus diegosuarezi; missing anatomy, pose, skin 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 Jurassic[1]
DIETHerbivoreEvidence and uncertainty in the dossier
TOTAL LENGTH2–3 mEstimate scope matters
FOSSILS FOUNDChile[1]
MEET THE ANIMAL
Meet Chilesaurus
Chilesaurus lived in Chile during the Late Jurassic. It walked on its hind legs and used a long tail for balance. Although parts of its body resemble those of meat-eating dinosaurs, its jaws and teeth fit plant feeding. Several skeletons give researchers a useful view of its unusual combination of features, rather than leaving them with just one mysterious bone. [D4]
That unusual combination makes its family-tree position difficult to establish. A 2017 analysis placed it near the beginning of the bird-hipped dinosaur group. Its backward-pointing pubis and straightened cheek teeth helped support that result. Even so, sharing a feature does not automatically make an animal a direct ancestor, and some important bird-hipped jaw features are absent. [D2]
A later study tested how the choice of comparison animals affects the answer. Adding different outgroups changed the position recovered for Chilesaurus. Researchers therefore continue to debate whether it belongs among theropods or ornithischians. Its story shows how a new fossil can challenge an old classification, and how careful testing can reveal uncertainty instead of immediately removing it. [D5]
PREHISTORIC ANIMAL DOSSIER
A life in profile.
The animal, the evidence, and the questions still open.
Later phylogenetic tests recover different placements depending on comparison taxa and character selection; a precise relationship remains unresolved. [D5]
Profile scope: The exhibit concerns Chilesaurus diegosuarezi from the Toqui Formation of southern Chile. [D1]
- Time
- Late Jurassic
- Fossil locations in this exhibit
- Chile
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
No mass estimate adopted. The inspected sources do not provide a specimen-bound body-mass estimate suitable for this comparison. [D1]
Diet and feeding
InferredHerbivory inferred from jaws and teeth.
Straightened leaf-cutting teeth support plant feeding; neither an exact menu nor a preserved meal is identified here. [D2]
Habitat and setting
InferredLate Jurassic terrestrial Toqui Formation.
Associated terrestrial vertebrates locate the fossil setting; burial alongside other animals does not establish a social group. [D1]
Movement
InferredBipedal movement with a balancing tail.
The museum describes two-legged posture; no fossil-supported speed is adopted. [D4]
Recognizable anatomy
InferredBird-like pelvis combined with other unusual skeletal traits.
A toothless front upper-jaw region and non-recurved cheek teeth occur without the typical ornithischian predentary bone. [D2]
Reproduction & life together
Reproduction and nesting
Not establishedNot established here
Egg and nest assignment unresolved. Neither the original description nor inspected posture study establishes Chilesaurus reproductive remains. [D3]
Mating and courtship
Not establishedNot established here
No supported mating display reconstructed. The reviewed articulated skeletons preserve anatomy and arm position, rather than a courtship sequence. [D3]
Social behavior
Not establishedNot established here
Several individuals do not prove herd living. Rapid burial and similar folded-arm positions permit behavioral interpretations, but everyday group organization remains unknown. [D3]
Dossier research & sources
Sources and inspection notes for the claims in this profile.
- Novas et al. (2015), An enigmatic plant-eating theropod from the Late Jurassic period of ChileNature · Accessed 2026-10-08Original abstract and accessible fossil figure captions inspected; paywalled main text not claimed as read. · Inspected: abstract
- Baron and Barrett (2017), A dinosaur missing-link? Chilesaurus and the early evolution of ornithischian dinosaursBiology Letters · Accessed 2026-10-08Full original reassessment inspected; ornithischian placement is a hypothesis superseded by continuing debate. · Inspected: page
- Chimento et al. (2017), Forelimb posture in Chilesaurus diegosuarezi and its behavioral and phylogenetic implicationsAMEGHINIANA / Universidad de Chile · Accessed 2026-10-08Institutional abstract inspected, including four articulated individuals with folded forelimbs; full repository PDF access was blocked. · Inspected: abstract
- Dinosaur Q&A: What was Chilesaurus diegosuarezi?Natural History Museum, London · Accessed 2026-10-08Complete indexed institutional interview inspected for anatomy and educational reference length; its definitive missing-link framing is qualified using later research. · Inspected: excerpt
- Baron (2024), The effect of character and outgroup choice on the phylogenetic position of ChilesaurusPalaeoworld · Accessed 2026-10-08Publisher abstract, introduction and accessible section excerpts inspected; online DOI dates to 2022, final volume to 2024. · Inspected: abstract
THE STORY IN THE FOSSILS
Evidence behind Chilesaurus
The unusual skeleton initially appeared to combine traits associated with different dinosaur groups. Articulated specimens show that those features really belonged together, rather than representing an accidental collection of unrelated bones. [1]
Changing the outgroup used in a family-tree analysis can move Chilesaurus. This is evidence that the comparison method matters, rather than proof that one placement has finally ended the debate. [5]
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.
- Novas et al. (2015), An enigmatic plant-eating theropod from the Late Jurassic period of ChileNature · Accessed 2026-10-08Original abstract and accessible fossil figure captions inspected; paywalled main text not claimed as read. · Inspected: abstract
- Baron and Barrett (2017), A dinosaur missing-link? Chilesaurus and the early evolution of ornithischian dinosaursBiology Letters · Accessed 2026-10-08Full original reassessment inspected; ornithischian placement is a hypothesis superseded by continuing debate. · Inspected: page
- Chimento et al. (2017), Forelimb posture in Chilesaurus diegosuarezi and its behavioral and phylogenetic implicationsAMEGHINIANA / Universidad de Chile · Accessed 2026-10-08Institutional abstract inspected, including four articulated individuals with folded forelimbs; full repository PDF access was blocked. · Inspected: abstract
- Dinosaur Q&A: What was Chilesaurus diegosuarezi?Natural History Museum, London · Accessed 2026-10-08Complete indexed institutional interview inspected for anatomy and educational reference length; its definitive missing-link framing is qualified using later research. · Inspected: excerpt
- Baron (2024), The effect of character and outgroup choice on the phylogenetic position of ChilesaurusPalaeoworld · Accessed 2026-10-08Publisher abstract, introduction and accessible section excerpts inspected; online DOI dates to 2022, final volume to 2024. · Inspected: abstract
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