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The collection/Adasaurus

EXHIBIT 139

Adasaurus

Adasaurus mongoliensis

Adasaurus is distinguished by a reduced claw on its second toe. [1]

Evidence profile

TWO WAYS TO PICTURE THE PAST

Compare the evidence with the familiar movie image. The illustrations are not to a shared scale.

01 / SKELETAL RECONSTRUCTION

A framework from the fossils

Adasaurus mongoliensis skull restoration with preserved rear skull in white and restored missing regions in grey.

Adasaurus mongoliensis skull restoration by PaleoNeolitic, based on the incomplete IGM 100/20 skull reviewed by Turner and colleagues. White regions represent preserved material; grey regions restore missing anatomy, notably much of the snout. The full outline and teeth in restored regions are comparative reconstruction, not a complete fossil skull. [1]

Adasaurus Skull.png · PaleoNeolitic. CC BY-SA 4.0. Current Commons 1280 px preview converted to WebP and proportionally reduced for thumbnail use. No cropping, mirroring, anatomical edits or compositing; diagram annotations retained. Derivatives retain CC BY-SA 4.0.

Skeletal mounts and drawings may restore missing parts; the caption identifies the displayed material.

02 / MOVIE-STYLE INTERPRETATION

A cinematic imagination

Illustrative reconstruction of Adasaurus mongoliensis; covering, colors and unpreserved anatomy are hypotheses.

Original cinematic interpretation of Adasaurus. Colors, soft tissues, scenery and missing anatomy are reconstructed artistic choices; this is not a directly observed individual or behavior. The reduced second-toe claw is distinguished from the enlarged sickle claws of many other dromaeosaurs; complete plumage and missing contours remain inferred. 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]
DIETCarnivoreEvidence and uncertainty in the dossier
TOTAL LENGTHSee the dossierEstimate scope matters
FOSSILS FOUNDMongolia[1]
CompareRead the dossierView the sources

MEET THE ANIMAL

Meet Adasaurus

Adasaurus was a dromaeosaurid dinosaur from Late Cretaceous Mongolia. Dromaeosaurids are the group often called raptors. Its fossils come from Bugin Tsav in the Nemegt Formation. The main specimen preserves part of the rear of the skull and an incomplete skeleton; a separate specimen includes tail bones and a foot. Together, they leave substantial gaps in its appearance. [S1]

Its second toe carried an unusually reduced claw, rather than the strongly enlarged claw familiar from many other raptors. Researchers also compare details of its cheek, skull roof and pelvis to distinguish it from related dinosaurs. The claw's shape suggests that its use may have differed, but does not preserve an observed attack or identify a particular prey animal. [S1]

One published size calculation estimated a body length of about 2.39 metres from its thighbone. This method compares a bone's length with body proportions in other dinosaurs to reconstruct missing anatomy. It is an estimate for the fossil used in that calculation, not a complete skeleton measured from nose to tail or a confirmed maximum for the species. [D4]

Overview sources
  1. Reexamination of Adasaurus mongoliensis from the Upper Cretaceous Nemegt Formation of MongoliaSociety of Vertebrate Paleontology; Kubota and Barsbold, 2006 meeting abstract, p.54A; Ghent University repository · Accessed 2026-10-04Inspected: abstract

PREHISTORIC ANIMAL DOSSIER

A life in profile.

The animal, the evidence, and the questions still open.

The unusual claw is preserved anatomy; its exact use during hunting remains uncertain. [D1] [D2]

Profile scope: Genus — Adasaurus; A. mongoliensis from Nemegt material. [D1]

Time
Late Cretaceous
Fossil locations in this exhibit
Mongolia
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 length

Inferred

About 2.39 m (femur-based reconstruction)

IGM 100/20; 2007 regression from 273 mm femur. Maturity unverified here. [D4]

Body mass

Inferred

About 44 kg (limb model)

IGM 100/20; measured femoral circumference; maturity unverified. [D3]

Diet and feeding

Inferred

Animal prey inferred

Carnivory is inferred comparatively from dromaeosaurid relationships; the preserved skull is largely posterior, and restored teeth are not evidence of a specific meal. [D1]

Habitat and setting

Source supported

Nemegt Formation, Bugin Tsav

Late Cretaceous Mongolia; locality alone does not define complete habitat preference. [D1]

Movement

Inferred

Two-legged movement inferred

Hindlimb and foot material support bipedal reconstruction; the reduced claw does not measure running speed. [D2]

Recognizable anatomy

Source supported

Reduced second-toe claw

The original description and revised diagnosis retain a small ungual on digit II. [D1] [D2]

Reproduction & life together

Reproduction and nesting

Not established

Not established here

Reviewed descriptions establish no assigned eggs or parental-care record. A fusion observation alone does not diagnose reproductive maturity. [D1] [D2]

Mating and courtship

Not established

Not established here

The original description does not identify sex-specific ornaments or a directly supported mating sequence. [D1]

Social behavior

Not established

Not established here

Type and referred material do not establish a social group or coordinated hunting. [D1]

Dossier research & sources

Sources and inspection notes for the claims in this profile.

  1. Carnivorous dinosaurs from the Cretaceous of Mongolia (Barsbold, 1983), Smithsonian translationJoint Soviet–Mongolian Paleontological Expedition / Smithsonian · Accessed 2026-10-02Original translated taxon section: named species, incomplete skull/postcrania, Bugin Tsav Nemegt locality, reduced second-toe ungual. · Inspected: page
  2. A Review of Dromaeosaurid Systematics and Paravian Phylogeny (Turner et al., 2012)Bulletin of the American Museum of Natural History · Accessed 2026-10-02Publisher-indexed diagnosis/foot excerpts, not full monograph. Reduced ungual retained; Bayanshire referrals 100/22,100/23 excluded. Fusion statement not securely matched to modeled type; no adult comparison. · Inspected: excerpt
  3. Benson et al. (2014), Dataset S1PLOS Biology · Accessed 2026-10-02Original XLS: IGM 100/20,43.8259 kg, measured femoral circumference 87 mm; specimen maturity not independently secured. · Inspected: page
  4. A Basal Dromaeosaurid and Size Evolution Preceding Avian Flight (Turner et al., 2007), Supporting Online MaterialScience / original supporting PDF mirror · Accessed 2026-10-02Original 35-page supplement methods p 24/Table S 1 p 25: IGM 100/20,2390 mm body-length regression from 273 mm femur, not a measured complete body. · Inspected: page

THE STORY IN THE FOSSILS

A raptor without the usual oversized claw.

A smaller second-toe ungual changes the familiar raptor silhouette. It cannot identify exactly how this dinosaur caught prey. [1]

The skull is incomplete; restorations distinguish the preserved rear skull from the reconstructed snout. [2]

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.

  1. Carnivorous dinosaurs from the Cretaceous of Mongolia (Barsbold, 1983), Smithsonian translationJoint Soviet–Mongolian Paleontological Expedition / Smithsonian · Accessed 2026-10-02Original translated taxon section: named species, incomplete skull/postcrania, Bugin Tsav Nemegt locality, reduced second-toe ungual. · Inspected: page
  2. A Review of Dromaeosaurid Systematics and Paravian Phylogeny (Turner et al., 2012)Bulletin of the American Museum of Natural History · Accessed 2026-10-02Publisher-indexed diagnosis/foot excerpts, not full monograph. Reduced ungual retained; Bayanshire referrals 100/22,100/23 excluded. Fusion statement not securely matched to modeled type; no adult comparison. · Inspected: excerpt
  3. Benson et al. (2014), Dataset S1PLOS Biology · Accessed 2026-10-02Original XLS: IGM 100/20,43.8259 kg, measured femoral circumference 87 mm; specimen maturity not independently secured. · Inspected: page
  4. A Basal Dromaeosaurid and Size Evolution Preceding Avian Flight (Turner et al., 2007), Supporting Online MaterialScience / original supporting PDF mirror · Accessed 2026-10-02Original 35-page supplement methods p 24/Table S 1 p 25: IGM 100/20,2390 mm body-length regression from 273 mm femur, not a measured complete body. · Inspected: page

FOLLOW YOUR CURIOSITY

Who will you meet next?

KEEP EXPLORING

More from the collection

Scaly featherless raptor in a dark forest, with a long level tail, grasping hands and a raised curved toe claw.
Movie-style interpretation
Late Cretaceous

Velociraptor

Velociraptor mongoliensis

Velociraptor mongoliensis was a lightly built meat-eater from Late Cretaceous Mongolia. Its long limbs, teeth and enlarged foot claws made it distinctive, while the Fighting Dinosaurs specimen records a remarkable interaction with a horned dinosaur.

CarnivoreMeet this animal