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EXHIBIT 189

Segnosaurus

Segnosaurus galbinensis

Segnosaurus had a downturned lower jaw and unusually complex teeth. These structures support a distinctive plant-feeding interpretation. [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 / FOSSIL VIEW

The evidence in the bones

Segnosaurus type hemimandibles MPC-D 100/80.

Published views of Segnosaurus galbinensis type jaw material, MPC-D 100/80. The downturned front and teeth are fossil anatomy. These panels are several views of jaw material, not separate animals, a complete head or direct evidence of a particular meal. [1]

Segnosaurus type hemimandibles MPC-D 100/80 · Lindsay E. Zanno, Khishigjav Tsogtbaatar, Tsogtbaatar Chinzorig & Terry A. Gates. CC BY 4.0. Converted to WebP and resized proportionally within verified native dimensions; no anatomical edits. Existing Commons crops or figure revisions are retained under the inspected file license.

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

02 / MOVIE-STYLE INTERPRETATION

A cinematic imagination

Artistic reconstruction of Segnosaurus; colors and restored soft tissues are illustrative.

Original cinematic interpretation of Segnosaurus. The distinctive downturned front lower jaw follows the described fossil. Full upper head, covering and living posture remain comparative; complex teeth do not document a meal or mating display. Lighting, colors and scenery are artistic choices; this image does not document directly observed behavior. 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[5]
DIETHerbivore (inferred)Evidence and uncertainty in the dossier
TOTAL LENGTHSee the dossierEstimate scope matters
FOSSILS FOUNDMongolia[2]
CompareRead the dossierView the sources

MEET THE ANIMAL

Meet Segnosaurus

Segnosaurus was a therizinosaur with particularly elaborate teeth. Folded cutting edges and additional small points made its tooth surfaces more complex. These features support specialized plant feeding. Differences from Erlikosaurus suggest different feeding roles, although the precise foods of either animal remain uncertain. [D1]

Its Mongolian rock formation records river and lake environments during the Late Cretaceous. That setting helps place the dinosaur in a changing landscape rather than an empty backdrop. Dating the formation establishes a regional time framework; it does not give the exact year when one Segnosaurus individual lived or prove that every fossil locality had identical conditions. [D5]

Body mass has been estimated using the relationship between thigh-bone length and weight. This is a mathematical reconstruction, rather than weighing an intact fossil animal. Such estimates depend on the model and the bones supplied to it. They help convey that Segnosaurus was substantial, while leaving uncertainty about a particular individual's weight and the largest adults. [D3]

Embryos described for other therizinosaur relatives do not identify Segnosaurus's own eggs. Similar family relationships are useful for comparison, but they cannot establish this genus's nest design, clutch size or parental care. [D6]

PREHISTORIC ANIMAL DOSSIER

A life in profile.

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

Its dental specialization may have helped divide food resources among therizinosaurs. That interpretation is comparative; fossil jaw anatomy does not preserve particular meals or living social groups. [D3]

Profile scope: Genus profile centered on S. galbinensis and type MPC-D 100/80, historically GIN 100/80. Separate referred limb material is not assumed to be one complete adult. [D2]

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 4 m; broad museum reference

The museum supplies this figure without an individual, maturity assessment or length calculation. It is retained as an unscoped restoration reference, not a verified adult size range. [D4]

Body mass

Inferred

Above 1.2 tonnes in the reviewed model set

The 2013 analysis uses femoral-length allometry and identifies Segnosaurus above 1,200 kg. The exact supplementary specimen row was unavailable; neither a precise individual estimate nor adult maximum is established here. [D3]

Diet

Inferred

Herbivory inferred from specialized dentition

Folded cutting edges and extra denticles support specialized feeding. Facultative versus obligate herbivory and exact food choices remain uncertain. [D1]

Habitat & fossil setting

Source supported

Bayanshiree river and lake deposits

Reviewed material comes from southeastern Mongolia. Formation-wide chronology is Cenomanian–Santonian; fluvial and lacustrine sediments supply environmental context without directly dating every individual. [D2] [D5]

Movement

Inferred

Bipedal reconstruction with four-digit feet

The original skeletal account documents a broad, noncompact four-digit pes and unusual pelvis. Bone proportions support a two-legged restoration, not a measured walking speed. [D2]

Distinctive anatomy

Source supported

Downturned dentary and 24 tooth positions

Type jaw MPC-D 100/80 preserves complex crown morphology. Some unusual distal triple carinae may be developmental abnormalities, so they are not described as universal adult features. [D1]

Reproduction & life together

Reproduction & nesting

Not established

Not established here

Chinese therizinosauroid embryos have been described, but the inspected abstract does not securely identify Segnosaurus as their producer. Its clutch size and parental care remain unresolved. [D6]

Courtship & mating

Not established

Not established here

Focused searches did not establish sexes, mate choice, mating seasons or a particular courtship display. Restored colors and feather arrangements are artistic interpretations.

Social behavior

Not established

Not established here

Referred material comes from more than one locality. This sampling does not demonstrate one herd or association with contemporaneous therizinosaurs in life. [D2]

Dossier research & sources

Sources and inspection notes for the claims in this profile.

  1. Specializations of the mandibular anatomy and dentition of Segnosaurus galbinensis (Theropoda: Therizinosauria)PeerJ; Zanno, Tsogtbaatar, Chinzorig & Gates (2016) · Accessed 2026-10-02Original full eighteen-page PDF inspected: type MPC-D 100/80, downturned dentary, 24 tooth positions, complex carinae and inferred dietary partitioning. Triple carinae may include developmental abnormality. · Inspected: page
  2. Segnosauria, a new infraorder of carnivorous dinosaursActa Palaeontologica Polonica; Barsbold & Perle (1980) · Accessed 2026-10-02Original nine-page PDF inspected: type and referred Segnosaurus inventory, pelvis and broad four-digit foot. Historical carnivorous interpretation is not adopted over later feeding research. · Inspected: page
  3. No evidence for directional evolution of body mass in herbivorous theropod dinosaursProceedings of the Royal Society B; Zanno & Makovicky (2012 online/2013 issue) · Accessed 2026-10-02Original full text inspected: femoral-length mass methodology and Segnosaurus model above 1,200 kg. Exact supplementary specimen row unavailable; no unverified 4.17-tonne figure adopted. · Inspected: page
  4. SegnosaurusNatural History Museum, London · Accessed 2026-10-02Current museum page inspected: unscoped 4.0 m length. Its carnivorous label conflicts with newer craniodental research and is not adopted. · Inspected: page
  5. Azhdarchid pterosaur diversity in the Bayanshiree Formation, Upper Cretaceous of the Gobi Desert, MongoliaPeerJ; Pêgas, Zhou & Kobayashi (2025) · Accessed 2026-10-02Original full PDF inspected: formation-wide Cenomanian–Santonian framework, upper beds and fluvial/lacustrine depositional environments; ages are not direct dates on individual therizinosaurs. · Inspected: page
  6. Embryos of therizinosauroid theropods from the Upper Cretaceous of China: diagnosis and analysis of ossification patternsActa Zoologica; Kundrát, Cruickshank, Manning & Nudds (2008) · Accessed 2026-10-02Original publisher abstract inspected: Chinese therizinosauroid embryos compared with Neimongosaurus and Erliansaurus; not a secure clutch assignment to this genus. · Inspected: abstract

THE STORY IN THE FOSSILS

Meet Segnosaurus.

Differences in body size can suggest distinct feeding niches. The 2013 study tests this proposal for differently sized therizinosaurs; it does not document competition or a particular meal. [3]

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. Specializations of the mandibular anatomy and dentition of Segnosaurus galbinensis (Theropoda: Therizinosauria)PeerJ; Zanno, Tsogtbaatar, Chinzorig & Gates (2016) · Accessed 2026-10-02Original full eighteen-page PDF inspected: type MPC-D 100/80, downturned dentary, 24 tooth positions, complex carinae and inferred dietary partitioning. Triple carinae may include developmental abnormality. · Inspected: page
  2. Segnosauria, a new infraorder of carnivorous dinosaursActa Palaeontologica Polonica; Barsbold & Perle (1980) · Accessed 2026-10-02Original nine-page PDF inspected: type and referred Segnosaurus inventory, pelvis and broad four-digit foot. Historical carnivorous interpretation is not adopted over later feeding research. · Inspected: page
  3. No evidence for directional evolution of body mass in herbivorous theropod dinosaursProceedings of the Royal Society B; Zanno & Makovicky (2012 online/2013 issue) · Accessed 2026-10-02Original full text inspected: femoral-length mass methodology and Segnosaurus model above 1,200 kg. Exact supplementary specimen row unavailable; no unverified 4.17-tonne figure adopted. · Inspected: page
  4. SegnosaurusNatural History Museum, London · Accessed 2026-10-02Current museum page inspected: unscoped 4.0 m length. Its carnivorous label conflicts with newer craniodental research and is not adopted. · Inspected: page
  5. Azhdarchid pterosaur diversity in the Bayanshiree Formation, Upper Cretaceous of the Gobi Desert, MongoliaPeerJ; Pêgas, Zhou & Kobayashi (2025) · Accessed 2026-10-02Original full PDF inspected: formation-wide Cenomanian–Santonian framework, upper beds and fluvial/lacustrine depositional environments; ages are not direct dates on individual therizinosaurs. · Inspected: page
  6. Embryos of therizinosauroid theropods from the Upper Cretaceous of China: diagnosis and analysis of ossification patternsActa Zoologica; Kundrát, Cruickshank, Manning & Nudds (2008) · Accessed 2026-10-02Original publisher abstract inspected: Chinese therizinosauroid embryos compared with Neimongosaurus and Erliansaurus; not a secure clutch assignment to this genus. · Inspected: abstract

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