What makes Maiasaura scientifically significant?

Maiasaura provides critical insights into the evolutionary radiation of Ornithopoda. Holotypes and fossil evidence indicate: Hundreds of skeletons, fossilized nests, clutches of eggs, hatchlings, and juvenile growth series.

Maiasaura (Maiasaura peeblesorum Horner & Makela, 1979) - Size, Diet & Cretaceous Period Facts

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Maiasaura (Maiasaura peeblesorum Horner & Makela, 1979) - Size, Diet & Cretaceous Period Facts | DinoOrigin

Evolutionary Taxonomy & Cladistics

View Dinosaur Phylogeny

Phylogenetic classification of Maiasaura peeblesorum Horner & Makela, 1979 based on peer-reviewed cladistic analyses of diagnostic skeletal synapomorphies.

Taxonomic Rank	Taxon / Clade	Diagnostic Context
Kingdom	Animalia	Monophyletic prehistoric clade
Phylum	Chordata	Monophyletic prehistoric clade
Clade	Dinosauria	Monophyletic prehistoric clade
Order	Ornithischia (Bird-Hipped Dinosaurs)	Characterized by a pelvis with a backwards-pointing pubis parallel to the ischium.
Suborder	Ornithopoda	Beaked, bipedal and facultatively quadrupedal herbivores with complex multi-layered dental batteries.
Genus	Maiasaura	Monophyletic prehistoric clade
Species	Maiasaura peeblesorum Horner & Makela, 1979	Specific authority designation

Anatomy & Physical Characteristics

Maiasaura holds an iconic place in paleontology. Unearthed at 'Egg Mountain' in the Two Medicine Formation of Montana by Jack Horner and Bob Makela in 1978, it provided the first undeniable proof that non-avian dinosaurs nurtured, fed, and protected their young in communal nesting colonies.

Fossil nests contained baby Maiasaura with worn teeth and immature limb cartilage, proving they remained in the nest for weeks and were fed by devoted parents.

Diagnostic Morphological Traits

Large hadrosaurid with a modest bony crest in front of the eyes, a duck-like beak, and strong hind limbs.

Comparative Scale & Biometrics

Anatomical dimensions relative to an average adult human (1.8 m / 6 ft tall)

Approx. 5.0× human length

Maiasaura (Length)8–9 m (26.2–29.5 ft)

Adult Human1.8 m (6.0 ft)

Length

8–9 m (26.2–29.5 ft)

Height

2.8–3.2 m (9.2–10.5 ft)

Estimated Mass

2.5–4.0 metric tons (5,512–8,818 lbs)

Diet & Feeding Ecology

All Herbivore Species

Trophic Guild: Herbivore

Conifers, ferns, woody twigs, and flowering plants pulverized with interlocking dental batteries.

Paleobiology & Behavior

Highly maternal hadrosaur that nested in communal colonies, bringing food to altricial hatchlings as demonstrated by fossil nesting sites. In the Two Medicine Formation, Maiasaura herds were constantly monitored by intelligent predatory troodontids like Troodon.

Habitat & Ecological Biome

Prehistoric Depositional Setting

Semi-arid upland plains with seasonal streams and conifer woodlands.

Fossil Evidence & Specimen Records

Preserved Skeletal Material & Bonebeds

Hundreds of skeletons, fossilized nests, clutches of eggs, hatchlings, and juvenile growth series.

Discovery & Taxonomic Naming History

Year of Discovery / Description1978

Type Specimen Locality & FormationTwo Medicine Formation, Teton County, Montana, United States

Discovered by Laurie Trexler and excavated by Jack Horner and Robert Makela.

Geological Era & Chronostratigraphy

Explore All Cretaceous Period Fauna

Cretaceous Period PeriodTemporal Interval: 79–76 Ma (million years ago)

The longest and final period of the Mesozoic Era, characterized by the rise of flowering plants, ceratopsians, hadrosaurs, tyrannosaurids, and concluding with the Chicxulub asteroid impact.

Where It Lived & Paleoenvironment

North America Dinosaurs

During the Mesozoic Era, continental drift progressively reconfigured land bridges, atmospheric currents, and regional precipitation regimes. Fossils of Maiasaura evidence its adaptation to the paleoenvironments of North America.

Paleogeographic RealmNorth America (North America)

Home to the fossil-rich Morrison Formation of the Late Jurassic and the Hell Creek and Dinosaur Park Formations of the Late Cretaceous.

Fossil Discovery Locality

Scientific Significance & Evolutionary Impact

The anatomical architecture of Maiasaura serves as a crucial benchmark in vertebrate paleontology, illustrating key adaptive radiations within Ornithopoda.

Phylogenetic Placement: Informs cladistic debates concerning the divergence, skull biomechanics, and skeletal evolution of Cretaceous Period fauna.
Paleoecological Guild: Documents trophic specialization (Herbivore) and predator-prey dynamics across its regional ecosystem.
Taphonomic Record: Hundreds of skeletons, fossilized nests, clutches of eggs, hatchlings, and juvenile growth series.

Frequently Asked Questions About Maiasaura

Scientifically verified answers based on peer-reviewed paleontological evidence.

Q1.When did Maiasaura live?

Maiasaura lived during the Cretaceous Period Period, approximately 79–76 Ma (million years ago). This places it within the Mesozoic Era.

Q2.How big was Maiasaura?

Paleontological estimates place Maiasaura at a length of 8–9 m (26.2–29.5 ft), a hip/standing height of 2.8–3.2 m (9.2–10.5 ft), and a body mass of 2.5–4.0 metric tons (5,512–8,818 lbs).

Q3.What was the diet of Maiasaura?

Classified as a herbivore, Maiasaura specialized in consuming Conifers, ferns, woody twigs, and flowering plants pulverized with interlocking dental batteries..

Q4.Where were Maiasaura fossils discovered?

Fossil specimens of Maiasaura have been recovered from Two Medicine Formation, Teton County, Montana, United States, with notable historic specimens documented in 1978. Discovered by Laurie Trexler and excavated by Jack Horner and Robert Makela.

Academic Literature & Peer-Reviewed References

Authoritative citations establishing the factual taxonomy, biometrics, and anatomy of Maiasaura.

NatureView Publication
Horner, J. R., & Makela, R. (1979). Nest of juveniles provides evidence of family structure among dinosaurs. Nature, 282(5736), 296-298. https://doi.org/10.1038/282296a0
Curated & Verified: 2026-09-24

Maiasaura

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