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EXHIBIT 137

Buitreraptor

Buitreraptor gonzalezorum

Buitreraptor had a long, low snout and numerous tiny teeth. [3]

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 / FOSSIL VIEW

The evidence in the bones

Buitreraptor gonzalezorum type MPCA 245 humerus, radius and ulna photographed from several views with scale bars.

Preserved forelimb bones of Buitreraptor gonzalezorum holotype MPCA 245, from Gianechini and colleagues’ 2018 anatomical study. Panels A–B show the humerus; C–E show radius and ulna; F details the ulna. Scale bars are 2 cm for A–E and 1 cm for F. These are fossil bones, without restored feathers or skin. [3]

Buitreraptor forelimb (MPCA 245).png · Federico A. Gianechini, Peter J. Makovicky, Sebastián Apesteguía and Ignacio Cerda. CC BY 4.0. Current Commons 1280 px preview converted to WebP, with a proportionally reduced thumbnail; original labels and scale bars retained. No cropping, mirroring, anatomical edits or compositing. Source license applies to these versions.

The photograph or figure shows the credited fossil material; displayed mounts and labels can include interpretation.

02 / MOVIE-STYLE INTERPRETATION

A cinematic imagination

Illustrative reconstruction of Buitreraptor gonzalezorum; covering, colors and unpreserved anatomy are hypotheses.

Original cinematic interpretation of Buitreraptor. Colors, soft tissues, scenery and missing anatomy are reconstructed artistic choices; this is not a directly observed individual or behavior. Its very long low snout anchors the view; complete plumage and missing soft tissues are comparative rather than directly preserved. 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[2]
DIETCarnivoreEvidence and uncertainty in the dossier
TOTAL LENGTHSee the dossierEstimate scope matters
FOSSILS FOUNDArgentina[2]
CompareRead the dossierView the sources

MEET THE ANIMAL

Meet Buitreraptor

Buitreraptor was a small carnivorous dinosaur from Late Cretaceous Argentina. The Natural History Museum gives an approximate length of 1.3 metres. This is an educational reconstruction, with no particular fossil or growth stage specified. It helps show the animal's general scale, but cannot tell us the largest size a fully grown Buitreraptor could reach. [D5]

Its long snout carried numerous tiny teeth. They were flattened from side to side and had grooves, but lacked the obvious sawlike edges seen in many other predatory dinosaurs. That unusual combination gives Buitreraptor a distinctive feeding profile. Teeth reveal the tools an animal had; they do not, by themselves, identify the species it actually ate. [D3]

Long lower legs and foot bones have led researchers to propose that Buitreraptor could run after small prey. This explanation comes from comparing limb proportions and how they might function. It is a hypothesis about movement and hunting, rather than a measured running speed or a preserved chase. Its exact prey and capture techniques remain uncertain. [D4]

PREHISTORIC ANIMAL DOSSIER

A life in profile.

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

Its distinctive dentition and long lower legs inform prey-capture hypotheses; published phylogenetic placement remains debated. [D4] [D7]

Profile scope: Genus — Buitreraptor; profile centered on B. gonzalezorum. [D1]

Time
Late Cretaceous
Fossil locations in this exhibit
Argentina
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 1.3 m (museum reference)

Educational reference without specimen or maturity; not an adult maximum. [D5]

Body mass

Inferred

About 3.3 kg (limb model)

MPCA 245; measured femoral circumference. Growing individual. [D6]

Diet and feeding

Inferred

Small animal prey inferred

Small, unserrated teeth and limb modeling favor capture of small prey; particular prey species are unverified. [D3] [D4]

Habitat and setting

Source supported

Candeleros dune-field setting

Cenomanian remains from La Buitrera, Río Negro, Argentina. Sediments indicate a paleodesert with intermittently wet areas. [D2]

Movement

Inferred

Two-legged, relatively cursorial

Long lower legs and metatarsi support running adaptations; fossil speed and endurance are unmeasured. [D4]

Recognizable anatomy

Source supported

Long snout; many tiny, grooved teeth

Teeth lack the conspicuous serrations of many northern dromaeosaurids. [D3]

Reproduction & life together

Reproduction and nesting

Not established

Not established here

Histology identifies growing subadults. A larger specimen was interpreted as sexually mature through growth slowing, not nesting evidence; breeding age and parental care remain unverified. [D2]

Mating and courtship

Not established

Not established here

Reviewed skeletal and functional studies establish no sex-specific display or mating sequence; proposed relationships with birds cannot supply one. [D4] [D7]

Social behavior

Not established

Not established here

Multiple referred skeletons document individuals; the reviewed material does not demonstrate coordinated hunting or a social group. [D2]

Dossier research & sources

Sources and inspection notes for the claims in this profile.

  1. The earliest dromaeosaurid theropod from South America (Makovicky, Apesteguía and Agnolín, 2005)Nature · Accessed 2026-10-02Original publisher abstract inspected: named genus, near-complete skeleton and South American occurrence. · Inspected: abstract
  2. Postcranial skeletal anatomy of the holotype and referred specimens of Buitreraptor gonzalezorum (Gianechini et al., 2018)PeerJ · Accessed 2026-10-02Full original material, stratigraphy and histology sections inspected: Cenomanian Candeleros setting; MPCA 245/238/471D subadults and separate MPCN-PV 598 growth interpretation. · Inspected: page
  3. The teeth of the unenlagiine theropod Buitreraptor ... and the unusual dentition of Gondwanan dromaeosaurids (Gianechini et al., 2011)Acta Palaeontologica Polonica · Accessed 2026-10-02Original abstract inspected: tooth number, compression, grooves and absent denticles/carinae. · Inspected: abstract
  4. Differential locomotor and predatory strategies of Gondwanan and derived Laurasian dromaeosaurids (Gianechini, Ercoli and Díaz-Martínez, 2020)Journal of Anatomy · Accessed 2026-10-02Original full abstract, methods and functional discussion inspected; comparative limb proportions support inferred running/small-prey strategies, not observed behavior. · Inspected: page
  5. BuitreraptorNatural History Museum, London · Accessed 2026-10-02Institutional profile:1.3 m educational reference without specimen or maturity; carnivore, Late Cretaceous Argentina. · Inspected: page
  6. Benson et al. (2014), Rates of dinosaur body mass evolution ..., Dataset S1PLOS Biology · Accessed 2026-10-02Original XLS inspected: MPCA 245,3.3106 kg from measured femoral circumference 34 mm. Juvenile flag alone is not an adult assessment. · Inspected: page
  7. Phylogenetic relationships of Unenlagiidae among Paraves (Motta et al., 2025)Journal of Systematic Palaeontology · Accessed 2026-10-02Original publisher abstract proposes avialan placement for unenlagiids; phylogenetic hypothesis, not fossil flight observation. · Inspected: abstract

THE STORY IN THE FOSSILS

A small predator with unusual teeth.

Long jaws carried unusually small teeth without denticles. These preserved structures offer stronger evidence than an imagined menu. [3]

Growth marks reveal that the main studied skeletons were still growing. Their sizes cannot define a mature population range. [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. The earliest dromaeosaurid theropod from South America (Makovicky, Apesteguía and Agnolín, 2005)Nature · Accessed 2026-10-02Original publisher abstract inspected: named genus, near-complete skeleton and South American occurrence. · Inspected: abstract
  2. Postcranial skeletal anatomy of the holotype and referred specimens of Buitreraptor gonzalezorum (Gianechini et al., 2018)PeerJ · Accessed 2026-10-02Full original material, stratigraphy and histology sections inspected: Cenomanian Candeleros setting; MPCA 245/238/471D subadults and separate MPCN-PV 598 growth interpretation. · Inspected: page
  3. The teeth of the unenlagiine theropod Buitreraptor ... and the unusual dentition of Gondwanan dromaeosaurids (Gianechini et al., 2011)Acta Palaeontologica Polonica · Accessed 2026-10-02Original abstract inspected: tooth number, compression, grooves and absent denticles/carinae. · Inspected: abstract
  4. Differential locomotor and predatory strategies of Gondwanan and derived Laurasian dromaeosaurids (Gianechini, Ercoli and Díaz-Martínez, 2020)Journal of Anatomy · Accessed 2026-10-02Original full abstract, methods and functional discussion inspected; comparative limb proportions support inferred running/small-prey strategies, not observed behavior. · Inspected: page
  5. BuitreraptorNatural History Museum, London · Accessed 2026-10-02Institutional profile:1.3 m educational reference without specimen or maturity; carnivore, Late Cretaceous Argentina. · Inspected: page
  6. Benson et al. (2014), Rates of dinosaur body mass evolution ..., Dataset S1PLOS Biology · Accessed 2026-10-02Original XLS inspected: MPCA 245,3.3106 kg from measured femoral circumference 34 mm. Juvenile flag alone is not an adult assessment. · Inspected: page
  7. Phylogenetic relationships of Unenlagiidae among Paraves (Motta et al., 2025)Journal of Systematic Palaeontology · Accessed 2026-10-02Original publisher abstract proposes avialan placement for unenlagiids; phylogenetic hypothesis, not fossil flight observation. · Inspected: abstract

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