Ugrunaaluk
"ancient grazer"
- Lived
- 72 to 66 million years ago, Late Cretaceous
- Diet
- Herbivore
- Group
- Ornithopods, Hadrosauridae
- Found in
- United States
- Named by
- Mori et al. 2016
Where its fossils were found
The evidence
Today
70 million years ago
Habitat
A low coastal plain in Arctic Alaska, crossed by river channels and flooded at intervals. Nanuqsaurus and Pachyrhinosaurus lived in the same region, which experienced long winter darkness.
Field notes
About Ugrunaaluk
What it was like
Ugrunaaluk was a duck-billed plant eater, known from the bones of many young animals. It had a broad beak and rows of grinding teeth.
Many scientists think it is simply Edmontosaurus, and that its bones look different only because they come from young animals.
Its world
It lived about 72 to 66 million years ago, at the end of the Late Cretaceous, in what is now northern Alaska, in the United States. Its bones come from the Prince Creek Formation, far to the north, where it shared the land with the tyrannosaur Nanuqsaurus and the horned Pachyrhinosaurus. It lived through long, dark winters.
How it was found
Mori and colleagues named Ugrunaaluk in 2016. Its name comes from a word in a local native language.
Field gallery
More views of Ugrunaaluk
Scenes reconstructed from the available fossil evidence.
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 Ugrunaaluk.
The evidence
The science behind Ugrunaaluk
Which parts of the picture come from its own bones, and which come from its relatives.
From its own fossils
- The bones used to name Ugrunaaluk come from separate individuals in a bonebed dominated by young duck-billed dinosaurs.
- The jaws carried tightly packed rows of teeth for processing plants.
- A later skull study found that features used to distinguish Ugrunaaluk also occur in Edmontosaurus or change as it grows.
Borrowed from relatives
- Edmontosaurus provides the main comparison for restoring the adult head and body.
Still unknown
- Experts disagree about whether Ugrunaaluk is distinct from Edmontosaurus, and which species the northern bones represent.
- How the head changed between the known young animals and fully grown adults.
- Its color.
Discovery timeline
- 2016Named itMori, Druckenmiller & Erickson
- 2019Same rocksTakasaki et al.
- 2020RedescriptionTakasaki et al.
- 2023Growing upSöderblom et al.
Key papers
The research behind what we know of Ugrunaaluk
Named it
Named Ugrunaaluk from mostly immature duck-billed dinosaur bones and proposed skull features separating it from Edmontosaurus.
A new Arctic hadrosaurid (Dinosauria: Hadrosauridae) from the Prince Creek Formation (lower Maastrichtian) of northern Alaska. Acta Palaeontologica Polonica 61
Read the paper : A new Arctic hadrosaurid (Dinosauria: Hadrosauridae) from the Prince Creek Formation (lower Maastrichtian) of northern Alaska (opens in a new tab)Same rocks
Identified a skull bone of a hollow-crested duck-billed dinosaur in the same bonebed, alongside the animals called Ugrunaaluk.
The First Definite Lambeosaurine Bone From the Liscomb Bonebed of the Upper Cretaceous Prince Creek Formation, Alaska, United States. Scientific Reports 9
Read the paper : The First Definite Lambeosaurine Bone From the Liscomb Bonebed of the Upper Cretaceous Prince Creek Formation, Alaska, United States (opens in a new tab)Redescription
Reexamined skull bones and concluded that the animals named Ugrunaaluk belong to Edmontosaurus, with their species unresolved.
Re-examination of the cranial osteology of the Arctic Alaskan hadrosaurine with implications for its taxonomic status. PLOS ONE 15: e0232410
Read the paper : Re-examination of the cranial osteology of the Arctic Alaskan hadrosaurine with implications for its taxonomic status (opens in a new tab)Growing up
Compared lower-jaw growth in the northern animals and Edmontosaurus, finding results compatible with competing taxonomic interpretations.
The dentary of hadrosauroid dinosaurs: evolution through heterochrony. Palaeontology 66
Read the paper : The dentary of hadrosauroid dinosaurs: evolution through heterochrony (opens in a new tab)
Close relatives
Other members of Hadrosauridae
Sources: Wikidata