Maiasaura

Horner & Makela, 1979 MAY-ya-SAWR-a

From Greek 'maia' (good mother) and 'saura' (the feminine form of sauros, lizard); meaning 'good mother lizard' or 'good mother reptile', referring to evidence of parental care

83.6–72.2 million years ago Campanian, Late Cretaceous

Late Cretaceous stages

Maiasaura is a large herbivorous saurolophine hadrosaurid ("duck-billed") dinosaur genus that lived in the area currently covered by the state of Montana and the Canadian province of Alberta, in the Upper Cretaceous (mid to late Campanian), from 86.3 to 70.6 million years ago. Maiasaura is the state fossil of Montana.

Diagnosis

Wide elongate facial region
Short naris located on anterior end of snout with extensive lateral facial region
Short wide premaxillary bill with deflected border similar to lambeosaurs
Small solid incipient crest above and between orbits, formed by nasal and frontal bones
Nasals concave anterior to incipient crest
Dentary teeth with long and narrow enamel crown
Predentary wide and very shallow with round, evenly spaced, denticulate processes

Species

Maiasaura peeblesorum Horner & Makela, 1979

Type species

Named for the families of John and James Peebles, on whose land the holotype and associated nesting site were discovered in Montana.

Holotype: YPM-PU 22405 , Yale Peabody Museum of Natural History
Material: Skull with partial right dentary and predentary.
Horizon: upper Two Medicine Formation, Campanian, Late Cretaceous , 83.6–72.2 million years ago
Locality: James and John Peebles ranch, Montana, United States

References

Horner, J. R.; Makela, R. (1979). Nest of juveniles provides evidence of family structure among dinosaurs. Nature 282(5736): 296-298. Springer Science and Business Media LLC. doi:10.1038/282296a0 horner1979a
Jones, B. (2026). The Princeton Encyclopedia of Dinosaurs: Ornithischians. Princeton University Press.
Source of the hip height estimate.
jones2026a