Omnisaura

Dinosaur genus

Maiasaura

Horner and Makela 1979

Maiasaura is a dinosaur genus known from bones, found in rocks 83.6–72.2 million years old, in the United States.

Confidence labels
How sure are we?2 high7 medium1 lowHow we rate confidence

Confidence labels are switched off. Facts with low confidence, or where sources disagree, still carry a small dot: tap it for the reason.

At a glance

Data as of 5 October 2026
83.6–72.2 Ma
Triassic
Jurassic
Cretaceous
252 million years ago20114366

The last non-bird dinosaurs died out 66 million years ago. That's as far from us as the end of this bar.

Named by
Horner and Makela 1979
highhigh: PBDB and Wikidata agree.
Sources

Given by: Paleobiology Database. How it was chosen: PBDB leads.

Described in
J. R. Horner, R. Makela (1979). Nest of juveniles provides evidence of family structure among dinosaurs. Nature 282: 296–298. Read it
highhigh: PBDB gives this publication for the name; its author and year match the naming authority (Horner and Makela 1979), on which PBDB and Wikidata agree.
Sources

Given by: Paleobiology Database. The publication the Paleobiology Database gives as the authority for this genus name, usually the one that first named and described it.

Lived
Campanian, 83.6–72.2 million years ago
mediummedium: Only PBDB gives this; nothing contradicts it.
Omnisaura calculation83.6–72.2 million years ago, from its dated fossil records
mediummedium: Omnisaura's calculation from 4 confirmed PBDB records.
Sources

Given by: Paleobiology Database. How it was chosen: PBDB leads.

Fossils found in
United States
mediummedium: Only PBDB records it (4 records).
Sources

Given by: Paleobiology Database. How it was chosen: Union of all sources (ISO 3166).

Rock formations
Two Medicine
mediummedium: Only PBDB records it (4 records).
Sources

Given by: Paleobiology Database. How it was chosen: Canonical names, automatic and editor-approved matches applied.

Family
Hadrosauridae
mediummedium: Only PBDB gives this; nothing contradicts it.
Sources

Given by: Paleobiology Database. How it was chosen: PBDB leads.

Parent group
Brachylophosaurini
mediummedium: Only PBDB gives this; nothing contradicts it.
Sources

Given by: Paleobiology Database. How it was chosen: PBDB leads.

Species named in its records
Maiasaura peeblesorum
Sources

Given by: Paleobiology Database (the species its fossil records are identified as).

Diet
herbivore (inferred for its group)
mediummedium: Only PBDB gives this, and it infers it for the whole of Ornithopoda, the group this genus belongs to, not from this genus's own fossils.
Sources

Given by: Paleobiology Database. How it was chosen: PBDB, inferred from a group the genus belongs to.

Way of life
ground dwelling, gregarious (inferred for its group)
lowlow: PBDB infers this way of life for the whole of Ornithischia; behaviour is rarely known for one genus.
Sources

Given by: Paleobiology Database. How it was chosen: PBDB, inferred from a group the genus belongs to.

Known from
Bones
Sources

Given by: Paleobiology Database (what the name was based on).

Sources: Paleobiology Database (CC BY 4.0), Wikidata (CC0 1.0)Confidence levels and gaps are Omnisaura's own assessment.

Gaps are answers

What isn't known yet

  • Type species: no source we use gives it yet.
  • Order: no source we use gives it yet.
  • Common names: no source we use gives it yet.
  • What it was named after: no source we use gives it yet.
  • Held back: 3 fossil records left out: identified only tentatively (for example "cf.", "?" or the name in quotation marks).
  • Resting on one source: 4 facts come from a single source with nothing against them (rated medium): parent group (PBDB); family (PBDB); age (headline) (PBDB); diet (PBDB).

Size and appearance aren't covered yet, and diet and way of life only as PBDB infers them for the wider group. Omnisaura leaves the rest out rather than guess.

Where sources disagree

None open. Where our sources overlap, they agree on everything shown here.

Did it meet…?

?

Same time, different places. Their fossils overlap in age, 83.6 to 72.2 million years ago, but no rock formation holds both.

Going by the ages and rock formations of their dated fossils, as on the map. Compare their fossil sites on the map.

Connections

Genera linked to Maiasaura by where and when their fossils were found, by classification and by who named them. Select a name to open its page.

MaiasauraSame rocks, same timeSame familySame naming authorAlso found in United StatesHypacrosaurusDaspletosaurusOohkotokiaOrodromeusand 24 moreAcheralichnusAcristavusAdelolophusAdynomosaurusand 35 moreCerasinopsRubeosaurusand 1 moreSaurornitholestesStegocerasAgujaceratopsRichardoestesiaand 78 more

Same rocks, same time 28

Genera found in the same rock units, from rocks of overlapping age, the most shared fossil sites first.

HypacrosaurusDaspletosaurusOohkotokiaOrodromeusTroodonBrontotholusPrismatoolithusProsaurolophusSaurornitholestesSpheroolithusAchelousaurusCerasinopsContinuoolithusEiniosaurusEuoplocephalusGryposaurusand 12 more

Named by Horner and Makela 3

Genera whose naming authority includes the same surname. The authority has no initials, so different people who share a surname can appear together.

CerasinopsOrodromeusRubeosaurus

Found in United States 82

Other genera found in United States, from rocks of overlapping age, the most fossil sites there first.

SaurornitholestesStegocerasAgujaceratopsRichardoestesiaKritosaurusTroodonParasaurolophusDaspletosaurusParonychodonPentaceratopsGryposaurusHypacrosaurusOrnithomimusAppalachiosaurusOrodromeusUtahceratopsand 66 more

Credits

Where this page comes from

  • Paleobiology DatabaseCC BY 4.0 · fossil records, ages, classification
  • WikidataCC0 1.0 · names and identifiers
  • OmnisauraOmnisaura editorial · confidence levels and gaps
  • PaleoMAP PaleoCoastlines (Kocsis and Scotese 2021)CC BY 4.0 · ancient coastlines on the small map
  • Natural EarthPublic domain · today's coastlines

Pictures linked from this page are credited beside each one, with their own licences; the full list is in the JSON download.