Einiosaurus
eye-nee-oh-SORE-us
"bison lizard"
- Lived
- 84 to 72 million years ago, Late Cretaceous
- Diet
- Herbivore
- Length
- estimates range from 4.5 to 6 m (15 to 20 ft)
- Group
- Ceratopsians, Ceratopsidae
- Found in
- United States
- Named by
- Sampson 1994
Where its fossils were found
The evidence
Today
80 million years ago
Habitat
The Two Medicine Formation in Montana records inland river plains with dry periods. Other dinosaurs from these rocks include Maiasaura and Daspletosaurus.
Field notes
About Einiosaurus
What it was like
Einiosaurus was a horned plant eater between 4.5 and 6 meters (15 to 20 feet) long. Its nose horn curved sharply forward and down, like a bottle opener, and a pair of long spikes rose from the back of its frill.
It walked on four legs and cut plants with a narrow, hooked beak.
Its world
It lived about 84 to 72 million years ago, in the Late Cretaceous, in what is now Montana. Its fossils come from the Two Medicine Formation, where it lived beside the horned Achelousaurus, the duck-bill Maiasaura and the tyrannosaur Daspletosaurus.
Its bones were found in bonebeds holding several animals together, which suggests it lived in herds, or at least gathered in groups.
How it was found
Sampson named Einiosaurus in 1994. Its name comes from a word for bison in a local native language.
Field gallery
More views of Einiosaurus
Scenes reconstructed from the available fossil evidence.
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Lived alongside
Found in the same rock formations
A rock formation can hold fossils laid down millions of years apart, so not every animal here met Einiosaurus.
The evidence
The science behind Einiosaurus
Which parts of the picture come from its own bones, and which come from its relatives.
From its own fossils
- Adult skulls have a nose horn that bends forward and down, rounded knobs above the eyes and a pair of long, straight frill spikes.
- Bonebeds contain skulls and body bones from several animals of different ages.
- A partly grown skull has a nearly adult-sized frill but a shorter face and less developed facial ornaments.
Borrowed from relatives
- Its own body bones guide the basic build, with Centrosaurus and Styracosaurus helping restore missing parts of the skeleton.
Still unknown
- Its color and the appearance of the skin over its frill.
- How it used its curved nose horn.
- Whether its bonebeds represent lasting herds or temporary gatherings.
Discovery timeline
- 1994Named itSampson
- 1995Full descriptionSampson
- 1997Growing upSAMPSON, RYAN & TANKE
- 2021Growing upWilson & Scannella
Key papers
The research behind what we know of Einiosaurus
Named it
Introduced Einiosaurus and Achelousaurus, two horned dinosaurs from the Two Medicine Formation.
Two new horned dinosaurs (Ornithischia: Ceratopsidae) from the Upper Cretaceous Two Medicine Formation, Montana, USA. Journal of Vertebrate Paleontology 14: 44A
No link available
Full description
Described skulls and body bones from bonebeds and linked Einiosaurus with Achelousaurus and Pachyrhinosaurus.
Two new horned dinosaurs from the upper Cretaceous Two Medicine Formation of Montana; with a phylogenetic analysis of the Centrosaurinae (Ornithischia: Ceratopsidae). Journal of Vertebrate Paleontology 15: 743-760
Read the paper : Two new horned dinosaurs from the upper Cretaceous Two Medicine Formation of Montana; with a phylogenetic analysis of the Centrosaurinae (Ornithischia: Ceratopsidae) (opens in a new tab)Growing up
Compared young and adult horned dinosaurs, showing that their distinctive horns and frills developed late in growth.
Craniofacial ontogeny in centrosaurine dinosaurs (Ornithischia: Ceratopsidae): taxonomic and behavioral implications. Zoological Journal of the Linnean Society 121: 293-337
Read the paper : Craniofacial ontogeny in centrosaurine dinosaurs (Ornithischia: Ceratopsidae): taxonomic and behavioral implications (opens in a new tab)Growing up
Described a partly grown Einiosaurus skull with a large frill and immature facial ornaments, tracing changes in the knobs above its eyes.
Comparative cranial osteology of subadult eucentrosauran ceratopsid dinosaurs from the Two Medicine Formation, Montana, indicates sequence of ornamentation development and complex supraorbital ontogenetic change. Acta Palaeontologica Polonica 66
Read the paper : Comparative cranial osteology of subadult eucentrosauran ceratopsid dinosaurs from the Two Medicine Formation, Montana, indicates sequence of ornamentation development and complex supraorbital ontogenetic change (opens in a new tab)
Close relatives
Other members of Ceratopsidae
Sources: Wikidata