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EXHIBIT 109

Riojasaurus

Riojasaurus incertus

Riojasaurus was a robust sauropodomorph from Late Triassic Argentina. Its small skull and unusual teeth became known through a skeleton smaller than the headless type. [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

Riojasaurus skull cast displayed in Copenhagen, with narrow jaws and small teeth.

Riojasaurus skull cast in Copenhagen. The cast illustrates cranial form; the source file gives no individual inventory or maturity and is not a measured whole-body specimen. [1]

Riojasaurus skull · FunkMonk. CC BY 3.0. Resized proportionally and converted to WebP; no anatomical edits. Same source license applies.

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

02 / MOVIE-STYLE INTERPRETATION

A cinematic imagination

Artistic reconstruction of Riojasaurus; colors and soft tissues are illustrative.

Original cinematic interpretation of Riojasaurus incertus. Colors, soft tissues, scenery and missing anatomy are reconstructed artistic choices; this is not a directly observed individual or behavior. Posture and hand stance remain comparative interpretations. 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 Triassic[1]
DIETHerbivoreEvidence and uncertainty in the dossier
TOTAL LENGTHSee the dossierEstimate scope matters
FOSSILS FOUNDArgentina[1]
CompareRead the dossierView the sources

MEET THE ANIMAL

Meet Riojasaurus

Riojasaurus was a Late Triassic dinosaur from Argentina. Its museum profile allows a plant-based diet or omnivory, meaning food from both plants and animals. That uncertainty should stay visible rather than becoming a precise menu. A rounded length reference of 5.2 metres also lacks a named individual or growth stage, so it is not an adult maximum. [D6]

How it usually moved is debated. Limb analysis in a thesis favors a four-legged interpretation while leaving some two-legged movement possible. A later scientific synthesis describes Riojasaurus as bipedal, meaning two-legged. These differing reconstructions cannot supply one measured gait sequence. Comparing limb proportions can test movement ideas, but it does not preserve the animal walking. [D4] [D5]

Historical naming adds another layer. An inspected systematic comparison includes Strenusaurus within Riojasaurus rather than treating it as another genus. A fossil profile is therefore built from both anatomy and identity: before comparing bodies or behavior, researchers must be clear about which dinosaur the names refer to. [D2]

PREHISTORIC ANIMAL DOSSIER

A life in profile.

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

The first described skull belongs to referred ULR 56, substantially smaller than the type. Research interpretations disagree about how consistently this animal walked on four legs. [D1] [D4] [D5]

Profile scope: Genus profile centered on Riojasaurus incertus, including the reviewed synonym Strenusaurus. Different reconstruction references are not treated as an adult species range. [D2]

Time
Late Triassic
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 5.2 m; museum reference

The current directory does not identify an individual or life stage. A separate historical mass model uses a 10 m outline; these references are not endpoints of an adult species range. [D6] [D7]

Body mass

Inferred

About 3.0 tonnes; historical outline model

Seebacher’s Table 2 integrates a reconstructed 10 m body outline with width and density assumptions. No specimen or maturity is specified; this does not match the museum’s 5.2 m reference. [D7]

Diet

Inferred

Plants likely; omnivory unresolved

The museum allows herbivory or omnivory. Skull material has mostly conical teeth with minute denticles, rather than a simple leaf-shaped tooth pattern; the reviewed evidence does not establish a detailed menu. [D6] [D1]

Habitat & fossil setting

Source supported

Los Colorados Formation, La Rioja

The described Argentinian material is Late Triassic. The reviewed skull study establishes locality and geological unit, but does not resolve individual habitat preferences or a detailed seasonal climate. [D1]

Movement

Debated

Bipedal versus quadrupedal habits debated

Traditional anatomy and Fechner’s limb analysis favor quadrupedal interpretations while allowing bipedality. Maidment and Barrett instead describe it as bipedal. A habitual gait cannot be settled from these differing interpretations alone. [D4] [D5]

Distinctive anatomy

Source supported

Robust build with a small, unusual-toothed head

The type lacks a skull. ULR 56 supplies a roughly 25 cm skull and conical teeth, but is about 35 percent smaller than the type; its proportions cannot be silently transferred to every individual. [D1]

Reproduction & life together

Reproduction & nesting

Not established

Not established here

Reviewed genus-specific sources do not establish assigned eggs, nesting grounds, incubation behavior or parental care. Other early sauropodomorph nesting discoveries remain broader comparisons.

Courtship & mating

Not established

Not established here

Focused searches and reviewed anatomical studies do not establish calls, display behavior, mate choice or sex-specific traits.

Social behavior

Not established

Not established here

Young and adult skeletons are represented in collections, but their number alone does not establish stable herds, age-segregated groups or family relationships. [D6]

Dossier research & sources

Sources and inspection notes for the claims in this profile.

  1. Notes on the first skull and jaws of Riojasaurus incertus from the Late Triassic of La Rioja, ArgentinaAmeghiniana; Bonaparte & Pumares (1995), Smithsonian-hosted translation · Accessed 2026-10-02Primary translated text inspected: headless PVL 3808 type, skull-bearing ULR 56 about 35 percent smaller, skull/teeth and traditional quadrupedal interpretation. Historical phylogenetic proposals are not adopted. · Inspected: excerpt
  2. Anatomy and systematics of Thecodontosaurus antiquus from the Upper Triassic of Southwest EnglandJournal of Vertebrate Paleontology; Benton, Juul, Storrs & Galton (2000), author-deposited published paper · Accessed 2026-10-02Table 1, based on specimens studied first-hand, lists Riojasaurus with Strenusaurus synonymy. Thecodontosaurus biology is not assigned to Riojasaurus. · Inspected: excerpt
  3. A revision of the parainfraclass Archosauria, excluding the advanced CrocodyliaMesozoic Meanderings 2; Olshevsky (1991), taxonomic revision · Accessed 2026-10-02Riojasaurus entry inspected for the exact former name Strenusaurus procerus; outdated higher-level classification is not adopted. · Inspected: excerpt
  4. The evolution of locomotion in the prosauropod dinosaursLMU Munich; Fechner (2009), doctoral research thesis · Accessed 2026-10-02Riojasaurus limb proportions and locomotion discussion: quadrupedal interpretation with facultative bipedality not excluded. Thesis status retained explicitly. · Inspected: excerpt
  5. The evolution of quadrupedality in ornithischian dinosaursJournal of Iberian Geology; Maidment & Barrett (2017) · Accessed 2026-10-02Primary synthesis discussion describes Riojasaurus as bipedal; this differs from the traditional and thesis interpretations. No measured gait sequence is available. · Inspected: excerpt
  6. RiojasaurusNatural History Museum, London · Accessed 2026-10-025.2 m reference without specimen/maturity, herbivory or omnivory, Argentina and multiple young/adult skeletons; collection count is not a herd observation. · Inspected: page
  7. A new method to calculate allometric length-mass relationships of dinosaursJournal of Vertebrate Paleontology; Seebacher (2001), author-deposited full text · Accessed 2026-10-02Methods and Table 2 inspected: Riojasaurus 10 m reconstructed outline and 3038.7 kg estimate, no individual inventory or life stage specified. · Inspected: excerpt

THE STORY IN THE FOSSILS

Meet Riojasaurus.

The headless type and the first skull-bearing skeleton are different individuals. Keeping their sizes separate allows the skull discovery to illuminate anatomy without turning a composite restoration into a measured fossil animal. [1]

Strenusaurus appears within Riojasaurus in the inspected systematic comparison. Reserving that historical name prevents the same animal from becoming another catalog entry. [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. Notes on the first skull and jaws of Riojasaurus incertus from the Late Triassic of La Rioja, ArgentinaAmeghiniana; Bonaparte & Pumares (1995), Smithsonian-hosted translation · Accessed 2026-10-02Primary translated text inspected: headless PVL 3808 type, skull-bearing ULR 56 about 35 percent smaller, skull/teeth and traditional quadrupedal interpretation. Historical phylogenetic proposals are not adopted. · Inspected: excerpt
  2. Anatomy and systematics of Thecodontosaurus antiquus from the Upper Triassic of Southwest EnglandJournal of Vertebrate Paleontology; Benton, Juul, Storrs & Galton (2000), author-deposited published paper · Accessed 2026-10-02Table 1, based on specimens studied first-hand, lists Riojasaurus with Strenusaurus synonymy. Thecodontosaurus biology is not assigned to Riojasaurus. · Inspected: excerpt
  3. A revision of the parainfraclass Archosauria, excluding the advanced CrocodyliaMesozoic Meanderings 2; Olshevsky (1991), taxonomic revision · Accessed 2026-10-02Riojasaurus entry inspected for the exact former name Strenusaurus procerus; outdated higher-level classification is not adopted. · Inspected: excerpt
  4. The evolution of locomotion in the prosauropod dinosaursLMU Munich; Fechner (2009), doctoral research thesis · Accessed 2026-10-02Riojasaurus limb proportions and locomotion discussion: quadrupedal interpretation with facultative bipedality not excluded. Thesis status retained explicitly. · Inspected: excerpt
  5. The evolution of quadrupedality in ornithischian dinosaursJournal of Iberian Geology; Maidment & Barrett (2017) · Accessed 2026-10-02Primary synthesis discussion describes Riojasaurus as bipedal; this differs from the traditional and thesis interpretations. No measured gait sequence is available. · Inspected: excerpt
  6. RiojasaurusNatural History Museum, London · Accessed 2026-10-025.2 m reference without specimen/maturity, herbivory or omnivory, Argentina and multiple young/adult skeletons; collection count is not a herd observation. · Inspected: page
  7. A new method to calculate allometric length-mass relationships of dinosaursJournal of Vertebrate Paleontology; Seebacher (2001), author-deposited full text · Accessed 2026-10-02Methods and Table 2 inspected: Riojasaurus 10 m reconstructed outline and 3038.7 kg estimate, no individual inventory or life stage specified. · Inspected: excerpt

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