Enigmacursor
"puzzle runner"
Type species Enigmacursor mollyborthwickae
- Lived
- 155 to 143 million years ago, Late Jurassic
- Diet
- Herbivore
- Group
- Early ornithischians
- Found in
- United States
- Named by
- Maidment and Barrett 2025
Where its fossils were found
The evidence
Today
150 million years ago
Habitat
It lived on floodplains beside rivers, where ferns and cycads grew. Stegosaurus, Allosaurus and Diplodocus lived in the Morrison Formation.
Field notes
About Enigmacursor
What it was like
Enigmacursor was a small plant eater that ran on its long hind legs. It is known from a partial skeleton. It was once thought to be a specimen of Nanosaurus, but closer study showed it was different.
Its world
It lived in the Late Jurassic, in what is now Colorado. It comes from the Morrison Formation, where it shared the land with Stegosaurus, Allosaurus, Diplodocus and Brontosaurus.
How it was found
Maidment and Barrett named Enigmacursor in 2025. The type species is Enigmacursor mollyborthwickae.
Field gallery
More views of Enigmacursor
Scenes reconstructed from the available fossil evidence.
1 of 2
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 Enigmacursor.
The evidence
The science behind Enigmacursor
Which parts of the picture come from its own bones, and which come from its relatives.
From its own fossils
- A partial skeleton preserves three teeth and much of the backbone, arms, hips and legs, but no skull bones. A combination of features in its back, hip and leg bones separates it from other small plant eaters.
- Its long hind legs, with a shinbone longer than the thigh bone, were suited to running. Both feet are nearly complete, with four clawed toes each.
- Only three poorly preserved bones of the left hand survive. The wrists and fingers of the mounted skeleton are modeled.
Borrowed from relatives
- The missing skull is restored from Lesothosaurus, and the neck and the end of the tail from Agilisaurus.
- The hands follow Minimocursor, whose wrist and fingers are preserved together.
Still unknown
- The shape of its skull and jaws.
- Its closest relative. The naming study found Yandusaurus, but with weak support.
- Its adult size.
Discovery timeline
- 2015Close relativePorro, Witmer & Barrett
- 2023Close relativeManitkoon et al.
- 2023Its worldMaidment
- 2025Named itMaidment & Barrett
Key papers
The research behind what we know of Enigmacursor
Close relative
Used scans to describe the skull and lower jaw of Lesothosaurus, an early small plant eater, from several damaged specimens.
Digital preparation and osteology of the skull of Lesothosaurus diagnosticus (Ornithischia: Dinosauria). PeerJ 3: e1494
Read the paper : Digital preparation and osteology of the skull of Lesothosaurus diagnosticus (Ornithischia: Dinosauria) (opens in a new tab)Close relative
Described Minimocursor, another early small plant eater whose left hand and wrist are preserved together.
A New Basal Neornithischian Dinosaur from the Phu Kradung Formation (Upper Jurassic) of Northeastern Thailand. Diversity 15: 851
Read the paper : A New Basal Neornithischian Dinosaur from the Phu Kradung Formation (Upper Jurassic) of Northeastern Thailand (opens in a new tab)Its world
Found that animal diversity increased through time in the Morrison Formation and varied geographically, with the highest diversity near the basin's center.
Diversity through time and space in the Upper Jurassic Morrison Formation, western U.S.A. Journal of Vertebrate Paleontology 43
Read the paper : Diversity through time and space in the Upper Jurassic Morrison Formation, western U.S.A. (opens in a new tab)Named it
Described Enigmacursor from a partial skeleton with teeth but no skull, and found Yandusaurus to be its closest relative in the analysis, with weak support.
Enigmacursor mollyborthwickae , a neornithischian dinosaur from the Upper Jurassic Morrison Formation of the western USA. Royal Society Open Science 12
Read the paper : Enigmacursor mollyborthwickae , a neornithischian dinosaur from the Upper Jurassic Morrison Formation of the western USA (opens in a new tab)
Close relatives
Other members of Neornithischia
Sources: Wikidata