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EXHIBIT 138

Unenlagia

Unenlagia comahuensis

Unenlagia combines bird-like shoulder features with a flightless body. [1] [2]

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

Unenlagia comahuensis known postcranial bones highlighted within a hypothetical body silhouette.

Known-material diagram of Unenlagia comahuensis by Conty. Colored pieces identify reported fossil material; the grey body, head, covering, hands and feet complete a hypothetical animal. The incomplete holotype does not preserve a skull or the entire external outline, and the silhouette is not a direct feather fossil or adult measurement. [1]

Unenlagia known material.JPG · Conty. Public domain. Current Commons 1280 px preview converted to WebP with proportional thumbnail reduction. No cropping, mirroring, anatomical edits or compositing; original diagram preserved.

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

02 / MOVIE-STYLE INTERPRETATION

A cinematic imagination

Illustrative reconstruction of Unenlagia comahuensis; covering, colors and unpreserved anatomy are hypotheses.

Original cinematic interpretation of Unenlagia. Colors, soft tissues, scenery and missing anatomy are reconstructed artistic choices; this is not a directly observed individual or behavior. The head and complete feather covering are comparative reconstructions, not preserved genus-specific skull or plumage. 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 LENGTH3–4 mEstimate scope matters
FOSSILS FOUNDArgentina[2]
CompareRead the dossierView the sources

MEET THE ANIMAL

Meet Unenlagia

Unenlagia was a carnivorous dinosaur from Late Cretaceous Argentina. This profile centers on Unenlagia comahuensis. The museum's general length reference is about 2.4 metres, but it is not tied to a particular individual or age. It should not be confused with a measured adult maximum, especially when different studies reconstruct an incomplete animal in different ways. [D5]

The original discovery drew attention to features of its shoulder and pelvis that resembled those of birds. These bones helped researchers investigate the evolutionary relationship between birds and other dinosaurs. A birdlike shoulder is a clue about anatomy, however, not a direct record of feathers or flight. Neither a flight display nor a particular courtship routine is preserved by those similarities. [D1]

Later research examined spaces inside its vertebrae, the bones that form the backbone. Internal cavities provide evidence relevant to air-filled parts of the skeleton. Such evidence concerns the animal's internal construction; it does not show the covering on its skin. Unenlagia is a useful reminder that a skeleton can reveal important evolutionary changes while leaving much of the living animal unknown. [D7]

PREHISTORIC ANIMAL DOSSIER

A life in profile.

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

An incomplete postcranial skeleton provides the body reference; its head and plumage remain reconstructions. [D2]

Profile scope: Genus — Unenlagia; U. comahuensis is the reference. U. paynemili was questioned as distinct. [D2]

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 3–4 m (holotype restoration)

MCF PVPH 78; incomplete skeleton. Adult interpretation rests on size and vertebral fusion. [D2]

Body mass

Inferred

About 63 kg (limb model)

MCF PVPH 78; measured femoral circumference. [D6]

Diet and feeding

Inferred

Carnivory inferred

Institutional classification; no skull or direct prey evidence in the described type material. [D5] [D2]

Habitat and setting

Source supported

Portezuelo sedimentary setting

Turonian–Coniacian mudstones at Sierra Portezuelo, Neuquén, Argentina; one partly articulated skeleton. [D2]

Movement

Inferred

Flightless biped inferred

Shoulder analysis supports folding predatory forelimbs rather than powered flight; hindlimbs support two-legged movement. [D2]

Recognizable anatomy

Source supported

Bird-like shoulder; pneumatic vertebrae

Shoulder features and CT-observed vertebral cavities document anatomy, not feathers or flight. [D1] [D7]

Reproduction & life together

Reproduction and nesting

Not established

Not established here

The type adult assessment does not establish breeding age, eggs, nests or parental care. [D2]

Mating and courtship

Not established

Not established here

Avian-like skeletal features do not identify a mating display; reviewed sources supply no directly attributed courtship evidence. [D1]

Social behavior

Not established

Not established here

The type was one individual without associated vertebrates; habitual social behavior remains unknown. [D2]

Dossier research & sources

Sources and inspection notes for the claims in this profile.

  1. New evidence concerning avian origins from the Late Cretaceous of Patagonia (Novas and Puerta, 1997)Nature · Accessed 2026-10-02Original abstract: named taxon and avian-like shoulder, pelvis and hindlimbs, not preserved plumage or behavior. · Inspected: abstract
  2. Osteology of Unenlagia comahuensis ... (Novas et al., 2021)The Anatomical Record · Accessed 2026-10-02Full original systematic, size, maturity, functional and locality sections: MCF PVPH 78 restoration 3–4 m, adulthood inferred from size/fusion, U.paynemili distinctness questioned. · Inspected: page
  3. Osteology of the unenlagiid theropod Neuquenraptor argentinus ... (Brissón Egli et al., 2017)Acta Palaeontologica Polonica · Accessed 2026-10-02Original abstract and taxonomic conclusion: Neuquenraptor/Unenlagia synonymy cannot be confirmed or dismissed. · Inspected: page
  4. Unenlagiid theropods: are they members of the Dromaeosauridae? (Agnolín and Novas, 2011)Anais da Academia Brasileira de Ciências · Accessed 2026-10-02Original indexed methods excerpt treats Neuquenraptor as a junior synonym of Unenlagia; later review is uncertain. · Inspected: excerpt
  5. UnenlagiaNatural History Museum, London · Accessed 2026-10-02Institutional carnivory/occurrence summary. Educational 2.4 m is not substituted for the scoped 2021 restoration. · Inspected: page
  6. Benson et al. (2014), Dataset S1PLOS Biology · Accessed 2026-10-02Original XLS: MCF PVPH 78,62.5187 kg, measured femoral circumference 99 mm. Maturity evaluated independently using Novas 2021. · Inspected: page
  7. Vertebral pneumaticity of the unenlagiine theropod Unenlagia comahuensis (Gianechini and Zurriaguz, 2021)Cretaceous Research · Accessed 2026-10-02Original abstract/indexed introductory excerpt: CT-observed internal vertebral pneumatic structure. · Inspected: abstract

THE STORY IN THE FOSSILS

A shoulder between familiar categories.

The shoulder helped frame debate over bird origins. [1]

CT scans reveal air-related spaces inside vertebrae. This anatomical evidence does not preserve the external covering. [7]

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. New evidence concerning avian origins from the Late Cretaceous of Patagonia (Novas and Puerta, 1997)Nature · Accessed 2026-10-02Original abstract: named taxon and avian-like shoulder, pelvis and hindlimbs, not preserved plumage or behavior. · Inspected: abstract
  2. Osteology of Unenlagia comahuensis ... (Novas et al., 2021)The Anatomical Record · Accessed 2026-10-02Full original systematic, size, maturity, functional and locality sections: MCF PVPH 78 restoration 3–4 m, adulthood inferred from size/fusion, U.paynemili distinctness questioned. · Inspected: page
  3. Osteology of the unenlagiid theropod Neuquenraptor argentinus ... (Brissón Egli et al., 2017)Acta Palaeontologica Polonica · Accessed 2026-10-02Original abstract and taxonomic conclusion: Neuquenraptor/Unenlagia synonymy cannot be confirmed or dismissed. · Inspected: page
  4. Unenlagiid theropods: are they members of the Dromaeosauridae? (Agnolín and Novas, 2011)Anais da Academia Brasileira de Ciências · Accessed 2026-10-02Original indexed methods excerpt treats Neuquenraptor as a junior synonym of Unenlagia; later review is uncertain. · Inspected: excerpt
  5. UnenlagiaNatural History Museum, London · Accessed 2026-10-02Institutional carnivory/occurrence summary. Educational 2.4 m is not substituted for the scoped 2021 restoration. · Inspected: page
  6. Benson et al. (2014), Dataset S1PLOS Biology · Accessed 2026-10-02Original XLS: MCF PVPH 78,62.5187 kg, measured femoral circumference 99 mm. Maturity evaluated independently using Novas 2021. · Inspected: page
  7. Vertebral pneumaticity of the unenlagiine theropod Unenlagia comahuensis (Gianechini and Zurriaguz, 2021)Cretaceous Research · Accessed 2026-10-02Original abstract/indexed introductory excerpt: CT-observed internal vertebral pneumatic structure. · Inspected: abstract

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