Body length
InferredAbout 9 m (museum reference)
A rounded reconstruction value with no stated specimen or maturity assessment; it is not an adult maximum. [D1]
EXHIBIT 77
Maiasaura
Maiasaura peeblesorum
Maiasaura preserves detailed evidence of growth, nesting and possible care.
TWO WAYS TO PICTURE THE PAST
Science & the silver screen
Compare the evidence with the familiar movie image. The illustrations are not to a shared scale.
01 / SCIENTIFIC RECONSTRUCTION
An animal, reconstructed
Image unavailableSide-view life reconstruction of Maiasaura peeblesorum with a small low skull crest, duckbill and long tail.The exhibit and its credited image source remain available.
Life reconstruction of Maiasaura peeblesorum by TotalDino, using the current revised artwork. Preserved anatomy informs the skeleton; missing parts, soft tissues, colors and markings remain interpretations. [1]
Maiasaura TD.png · TotalDino. CC BY 4.0. Commons-listed 1280px current preview resized proportionally for the thumbnail and converted to WebP; no anatomical edits. Same source license applies.
Scientific reconstruction is an interpretation; source credit does not certify every anatomical detail.
02 / MOVIE-STYLE INTERPRETATION
A cinematic imagination
Image unavailableIllustrative reconstruction of Maiasaura peeblesorum.The exhibit and its credited image source remain available.
Original cinematic interpretation of Maiasaura peeblesorum. Coloration, soft tissues and scenery are artistic choices; reconstructed proportions do not establish 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[2]
DIETHerbivoreEvidence and uncertainty in the dossier
TOTAL LENGTHSee the dossierEstimate scope matters
FOSSILS FOUNDMontana, USA[2]
MEET THE ANIMAL
Meet Maiasaura
Maiasaura was a plant-eating dinosaur from Late Cretaceous Montana. A beak and many food-processing teeth suited it to eating vegetation. Its fossils offer more than a body outline: nesting sites, young animals, and extensive bonebeds make it possible to investigate growth and reproduction. These different clues answer different questions about its life. [D1] [D2]
Thin sections of leg bones reveal how the animal grew. Some rings in a young Maiasaura formed within one year, so counting every ring as a birthday would give the wrong age. Researchers have to distinguish yearly pauses from other growth marks before turning a fossil bone into a life-history record. [D3]
Recent studies compare bone-related clues to metabolism and tooth wear in young and adults. Their results support ideas that hatchlings were dependent and may have received selected food. That does not preserve a parent feeding a chick or identify which parent provided care. Maiasaura's reputation for parenting rests on evidence that can be tested and revised, not a complete recording of family life. [D4] [D5]
PREHISTORIC ANIMAL DOSSIER
A life in profile.
The animal, the evidence, and the questions still open.
Care remains inferred.
Profile scope: Species — Maiasaura peeblesorum.
- Time
- Late Cretaceous
- Fossil locations in this exhibit
- Montana, USA
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 mass
InferredAbout 3,660 kg for ROM 44770
Limb-circumference estimate for an individual labeled mature; not a species-wide average or maximum. [D6]
Diet and feeding
InferredPlant-eating, with juvenile/adult differences
A 2026 study finds different wear patterns in young and adults. Selective provision of better-quality food is an interpretation, not preserved meals. [D5]
Habitat and setting
Source supportedTwo Medicine Formation, Montana
Nesting localities and extensive bonebeds place this species in a Late Cretaceous continental setting. Depositional occurrence does not identify one exclusive habitat. [D2]
Movement
InferredJuveniles and adults probably moved differently
The growth study discusses a proposed transition from bipedal juveniles toward quadrupedal adults. These postures are skeletal interpretations, not a directly observed life sequence. [D2]
Recognizable anatomy
Source supportedBeak and rows of food-processing teeth
The horny beak and many chewing teeth fit a hadrosaur adapted to processing vegetation. Individual soft tissues and colors remain reconstructed. [D1]
Reproduction & life together
Reproduction and nesting
DebatedNests and young; dependent hatchlings proposed
Nesting evidence supports reproduction. Earlier incapacity-based care arguments were challenged by mineralized neonatal pelvis and missing adult nest remains. A 2025 bone-derived metabolic comparison favors dependence. Provisioning, nest attendance and nest residence remain interpretations; feeding acts and incubation duration are not directly recorded. [D4]
Mating and courtship
Not establishedNot established here
The reviewed nesting, growth and metabolic studies do not establish mate choice, pairing or courtship displays.
Social behavior
InferredAggregations are supported by bonebed evidence
A largely single-species bonebed preserves many growth stages. Association supports animals gathering; transport and accumulation require interpretation, and do not establish permanent herd composition. [D2]
Dossier research & sources
Sources and inspection notes for the claims in this profile.
- MaiasauraNatural History Museum, London · Accessed 2026-10-02Museum profile; rounded reference size, diet, identity and geographic occurrence. Life stage and individual basis of size values are not specified. · Inspected: page
- Maiasaura, a model organism for extinct vertebrate population biology: a large sample statistical assessment of growth dynamics and survivorshipPaleobiology / Cambridge University Press · Accessed 2026-10-02Original study; tibial growth series, bonebed context, maturity estimates, body-size discussion and occurrence in the Two Medicine Formation inspected. · Inspected: page
- Maiasaura (Dinosauria: Hadrosauridae) Tibia Osteohistology Reveals Non-annual Cortical Vascular Rings in Young of the YearFrontiers in Earth Science · Accessed 2026-10-02Original histological study; young-of-year growth markers and distinction between annual and nonannual rings. · Inspected: page
- Neonatal state and degree of necessity for parental care in Maiasaura based on inferred neonatal metabolic ratesScientific Reports / Nature Portfolio · Accessed 2026-10-02Original study; bone-derived metabolic proxies, bird comparisons and inferred neonatal dependence. This tests a care hypothesis rather than observing parental feeding. · Inspected: page
- Tooth wear in juvenile and adult hadrosaurs: implications for parental care in MaiasauraPalaeogeography, Palaeoclimatology, Palaeoecology / Elsevier · Accessed 2026-10-02Publisher-indexed abstract inspected; juvenile/adult tooth-wear comparison and selective food-provisioning interpretation. Full publisher page was inaccessible. Published May 2026. · Inspected: excerpt
- Rates of Dinosaur Body Mass Evolution Indicate 170 Million Years of Sustained Ecological Innovation on the Avian Stem LineagePLOS Biology · Accessed 2026-10-02Original paper methods and downloaded Dataset S1 inspected; Full data and Mass estimates sheets identify specimen, maturity notes, limb measurements and calculated mass. Dataset retained locally for scope verification. · Inspected: page
THE STORY IN THE FOSSILS
A life history written in bone.
A young Maiasaura tibia can contain vascular rings that formed within one year. Reading every ring as an annual birthday would produce the wrong age. Histology must distinguish rapid growth from yearly pauses. [3]
Its reputation for care continues to be tested. Recent metabolic proxies and tooth wear favor dependence and possible food provisioning. Neither reveals which parent fed the young or how food was delivered. [4] [5]
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.
- MaiasauraNatural History Museum, London · Accessed 2026-10-02Museum profile; rounded reference size, diet, identity and geographic occurrence. Life stage and individual basis of size values are not specified. · Inspected: page
- Maiasaura, a model organism for extinct vertebrate population biology: a large sample statistical assessment of growth dynamics and survivorshipPaleobiology / Cambridge University Press · Accessed 2026-10-02Original study; tibial growth series, bonebed context, maturity estimates, body-size discussion and occurrence in the Two Medicine Formation inspected. · Inspected: page
- Maiasaura (Dinosauria: Hadrosauridae) Tibia Osteohistology Reveals Non-annual Cortical Vascular Rings in Young of the YearFrontiers in Earth Science · Accessed 2026-10-02Original histological study; young-of-year growth markers and distinction between annual and nonannual rings. · Inspected: page
- Neonatal state and degree of necessity for parental care in Maiasaura based on inferred neonatal metabolic ratesScientific Reports / Nature Portfolio · Accessed 2026-10-02Original study; bone-derived metabolic proxies, bird comparisons and inferred neonatal dependence. This tests a care hypothesis rather than observing parental feeding. · Inspected: page
- Tooth wear in juvenile and adult hadrosaurs: implications for parental care in MaiasauraPalaeogeography, Palaeoclimatology, Palaeoecology / Elsevier · Accessed 2026-10-02Publisher-indexed abstract inspected; juvenile/adult tooth-wear comparison and selective food-provisioning interpretation. Full publisher page was inaccessible. Published May 2026. · Inspected: excerpt
- Rates of Dinosaur Body Mass Evolution Indicate 170 Million Years of Sustained Ecological Innovation on the Avian Stem LineagePLOS Biology · Accessed 2026-10-02Original paper methods and downloaded Dataset S1 inspected; Full data and Mass estimates sheets identify specimen, maturity notes, limb measurements and calculated mass. Dataset retained locally for scope verification. · Inspected: page
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