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The collection/Alamosaurus

EXHIBIT 87

Alamosaurus

Alamosaurus sanjuanensis

Alamosaurus is a New Mexican titanosaur with fossil assignments reconsidered in 2025.

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

Gilmore’s 1922 plate of the Alamosaurus holotype left scapula, with dashed outlines indicating missing margins.

Gilmore’s 1922 Plate 1 records the Alamosaurus holotype scapula, USNM 10486. Dashed outlines reconstruct missing portions. The printed one-tenth scale no longer applies after digital resizing; this is a shoulder bone, not a complete skeleton. [7]

A new sauropod dinosaur from the Ojo Alamo Formation of New Mexico.pdf, Plate 1 · Charles W. Gilmore (publication); Smithsonian Institution / Biodiversity Heritage Library (scan). Public domain (United States). Plate 1 page preview resized proportionally and converted to WebP. No cropping, anatomical edits or upscaling.

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 Alamosaurus; colors and soft tissues are illustrative.

Original cinematic interpretation of Alamosaurus sanjuanensis. Full-body proportions remain uncertain because the type fossil is fragmentary. Coloration, soft tissues and scenery are artistic choices; this is not a measured individual. 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[8]
DIETHerbivoreEvidence and uncertainty in the dossier
TOTAL LENGTHSee the dossierEstimate scope matters
FOSSILS FOUNDNew Mexico, United States[8]
CompareRead the dossierView the sources

MEET THE ANIMAL

Meet Alamosaurus

Alamosaurus was named from Late Cretaceous fossils discovered in New Mexico. Its original shoulder blade is an important anchor for identifying the dinosaur. That bone was incomplete, and a pelvic bone found nearby could not confidently be assigned to the same individual. The earliest material therefore does not amount to one complete skeleton. [D7]

It is classified as a plant-eating sauropod. Familiar museum body-length figures should be treated carefully when they do not name a specimen, growth stage, or estimation method. A reference figure is useful for orientation, but it cannot turn a partial fossil into a measured animal or establish how large all members of a species grew. [D2]

Institutional descriptions reconstruct sauropods such as Alamosaurus walking on four supporting limbs. That broader body plan does not provide a measured speed or one exact stride for this dinosaur. The long-necked body in a restoration combines the preserved pieces with reconstructed proportions. Its silhouette is more complete than the original fossil, leaving some movement details and proportions uncertain. [D1]

PREHISTORIC ANIMAL DOSSIER

A life in profile.

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

The type scapula anchors this profile; body reconstructions remain uncertain.

Profile scope: Species focus: A. sanjuanensis; disputed referrals remain separate.

Time
Late Cretaceous
Fossil locations in this exhibit
New Mexico, United States
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

Not established

Not established here

NHM lists 21 m without specimen, maturity or method. The 2025 revision questions historical referrals; this is not a secure type-based length. [D2] [D8]

Body mass

Inferred

About 20 tonnes; type-scaled composite model

Paul’s 2025 model scales an approximate, incomplete regional-titanosaur composite to the holotype scapula. Type maturity and whole-body proportions remain unresolved; this is not an adult maximum. [D8]

Diet

Source supported

Plant-eater

The museum identifies herbivory. Precise foods and feeding height remain uncertain for the restricted genus. [D2]

Habitat & fossil setting

Source supported

Early Maastrichtian, New Mexico

The revision anchors Alamosaurus in the lower Ojo Alamo type occurrence. Historical terminal-Cretaceous Texas and Utah referrals require reassessment. [D8]

Movement

Inferred

Four-legged terrestrial walker

The institutional reconstruction follows the sauropod supporting-limb plan. Precise Alamosaurus gait, limb spacing and speed remain unresolved. [D1]

Distinctive anatomy

Source supported

Type shoulder blade

USNM 10486 preserves a gradually broadening left scapula, 155 cm long as preserved; Gilmore estimated 170 cm if complete. Bone length is not body length. [D7]

Reproduction & life together

Reproduction & nesting

Not established

Not established here

Focused nesting searches and reviewed specimens do not identify Alamosaurus eggs or clutches. Generic titanosaur nests cannot establish its parental care.

Courtship & mating

Not established

Not established here

Reviewed anatomical and behavioral research does not establish courtship, mate choice or mating posture.

Social behavior

Not established

Not established here

The historical Big Bend juvenile-herd interpretation concerns Texas referrals. A 2025 revision questions such assignments; securely applying that behavior to Alamosaurus requires reassessment. [D6] [D8]

Dossier research & sources

Sources and inspection notes for the claims in this profile.

  1. Alamosaurus—The Last of the Super-Giant Dinosaurs from New MexicoNew Mexico Bureau of Geology and Mineral Resources; Earth Matters (2024) · Accessed 2026-10-02Research-team overview of Alamosaurus geography and biology; its 33 tons/66,000 lb reference uses US short tons and lacks a named mass-estimated individual. This institutional account predates Paul 2025 and uses a broader historical referral scope. · Inspected: excerpt
  2. AlamosaurusNatural History Museum, London · Accessed 2026-10-02Museum 21 m reference, herbivory, type species and Late Cretaceous assignment; length specimen, life stage and method unspecified. · Inspected: page
  3. The first giant titanosaurian sauropod from the Upper Cretaceous of North AmericaActa Palaeontologica Polonica; Fowler & Sullivan (2011) · Accessed 2026-10-02Primary abstract: two large vertebrae and a partial femur referred to Alamosaurus; fragmentary comparative size evidence, not a complete measured body. Paul 2025 retains New Mexican referrals only provisionally. · Inspected: abstract
  4. A juvenile specimen of the sauropod dinosaur Alamosaurus sanjuanensis from the Upper Cretaceous of Big Bend National Park, TexasJournal of Paleontology; Lehman & Coulson (2002; online archive 2015) · Accessed 2026-10-02Original research abstract: juvenile cervical and pelvic anatomy, a shallow floodplain pond and species referral. The TMM 43621-1 genus referral is questioned in Paul 2025. · Inspected: abstract
  5. A juvenile specimen of Alamosaurus sanjuanensis: skeletal reconstruction sectionJournal of Paleontology; Lehman & Coulson (2002), repository-hosted published paper · Accessed 2026-10-02Indexed published paragraph on p169 inspected: composite adult reconstruction, doubled juvenile dimensions, TMM 41541 limb circumferences and 30-tonne mass model. TMM 41541 and the composite’s Alamosaurus identity are questioned in Paul 2025; this historical estimate no longer supplies the mass field. · Inspected: excerpt
  6. Evidence for gregarious behavior and age segregation in sauropod dinosaursPalaeogeography, Palaeoclimatology, Palaeoecology; Myers & Fiorillo (2009) · Accessed 2026-10-02Publisher abstract and indexed excerpts inspected: Big Bend assemblage interpreted as an age-segregated juvenile Alamosaurus herd; not direct adult behavior. Subsequent questioning of Texas referrals limits applying this historical interpretation to the restricted genus. · Inspected: abstract
  7. A new sauropod dinosaur from the Ojo Alamo formation of New Mexico (with two plates)Smithsonian Miscellaneous Collections; Charles W. Gilmore (1922) · Accessed 2026-10-02Original published description and Plate 1 inspected: holotype USNM 10486 scapula, paratype USNM 10487, locality, preserved versus reconstructed bone dimensions and uncertain same-individual association. · Inspected: page
  8. Stratigraphic and anatomical evidence for multiple titanosaurid dinosaur taxa in the Late Cretaceous (Campanian-Maastrichtian) of southwestern North AmericaGeology of the Intermountain West; Gregory S. Paul (2025) · Accessed 2026-10-02Official full published PDF downloaded and inspected, especially pp206 and 210-216: Utetitan naming, questioned referrals, restricted Alamosaurus scope, approximate composite models and Perot concerns. The original Gilmore specimen numbers 10486/10487 are retained; the revision repeatedly transposes them to 10846/10847. · Inspected: page

THE STORY IN THE FOSSILS

Meet Alamosaurus.

Paul’s 2025 revision names Utetitan from Utah skeleton USNM 15560 and treats key Texas specimens as indeterminate. These proposals change which fossils can inform Alamosaurus biology. [8]

Gilmore’s original shoulder blade and pelvic bone were found roughly 200 feet apart. Whether they belonged to one individual was uncertain even in 1922; a complete skeleton cannot be assumed. [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. Alamosaurus—The Last of the Super-Giant Dinosaurs from New MexicoNew Mexico Bureau of Geology and Mineral Resources; Earth Matters (2024) · Accessed 2026-10-02Research-team overview of Alamosaurus geography and biology; its 33 tons/66,000 lb reference uses US short tons and lacks a named mass-estimated individual. This institutional account predates Paul 2025 and uses a broader historical referral scope. · Inspected: excerpt
  2. AlamosaurusNatural History Museum, London · Accessed 2026-10-02Museum 21 m reference, herbivory, type species and Late Cretaceous assignment; length specimen, life stage and method unspecified. · Inspected: page
  3. The first giant titanosaurian sauropod from the Upper Cretaceous of North AmericaActa Palaeontologica Polonica; Fowler & Sullivan (2011) · Accessed 2026-10-02Primary abstract: two large vertebrae and a partial femur referred to Alamosaurus; fragmentary comparative size evidence, not a complete measured body. Paul 2025 retains New Mexican referrals only provisionally. · Inspected: abstract
  4. A juvenile specimen of the sauropod dinosaur Alamosaurus sanjuanensis from the Upper Cretaceous of Big Bend National Park, TexasJournal of Paleontology; Lehman & Coulson (2002; online archive 2015) · Accessed 2026-10-02Original research abstract: juvenile cervical and pelvic anatomy, a shallow floodplain pond and species referral. The TMM 43621-1 genus referral is questioned in Paul 2025. · Inspected: abstract
  5. A juvenile specimen of Alamosaurus sanjuanensis: skeletal reconstruction sectionJournal of Paleontology; Lehman & Coulson (2002), repository-hosted published paper · Accessed 2026-10-02Indexed published paragraph on p169 inspected: composite adult reconstruction, doubled juvenile dimensions, TMM 41541 limb circumferences and 30-tonne mass model. TMM 41541 and the composite’s Alamosaurus identity are questioned in Paul 2025; this historical estimate no longer supplies the mass field. · Inspected: excerpt
  6. Evidence for gregarious behavior and age segregation in sauropod dinosaursPalaeogeography, Palaeoclimatology, Palaeoecology; Myers & Fiorillo (2009) · Accessed 2026-10-02Publisher abstract and indexed excerpts inspected: Big Bend assemblage interpreted as an age-segregated juvenile Alamosaurus herd; not direct adult behavior. Subsequent questioning of Texas referrals limits applying this historical interpretation to the restricted genus. · Inspected: abstract
  7. A new sauropod dinosaur from the Ojo Alamo formation of New Mexico (with two plates)Smithsonian Miscellaneous Collections; Charles W. Gilmore (1922) · Accessed 2026-10-02Original published description and Plate 1 inspected: holotype USNM 10486 scapula, paratype USNM 10487, locality, preserved versus reconstructed bone dimensions and uncertain same-individual association. · Inspected: page
  8. Stratigraphic and anatomical evidence for multiple titanosaurid dinosaur taxa in the Late Cretaceous (Campanian-Maastrichtian) of southwestern North AmericaGeology of the Intermountain West; Gregory S. Paul (2025) · Accessed 2026-10-02Official full published PDF downloaded and inspected, especially pp206 and 210-216: Utetitan naming, questioned referrals, restricted Alamosaurus scope, approximate composite models and Perot concerns. The original Gilmore specimen numbers 10486/10487 are retained; the revision repeatedly transposes them to 10846/10847. · Inspected: page

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