Jurassic Dinos editorial · Updated · Source-based review
What was Enigmacursor?
Enigmacursor was a small plant-eating dinosaur from Late Jurassic North America. Its species is Enigmacursor mollyborthwickae, named in 2025. The fossils come from the Colorado part of the Morrison Formation.
The Morrison is famous for enormous dinosaurs, but its smaller animals are also important. Enigmacursor helps researchers investigate a portion of the ecosystem that has often received less attention than giant sauropods and predators.
Why does its name refer to a puzzle?
The genus name combines an idea of mystery with a running-related word. The mystery concerns the complicated history of small Morrison ornithischians. Older names were established from material that can be difficult to diagnose reliably when compared with today’s much larger fossil record.
The new specimen was initially presented as Nanosaurus. Detailed study instead supported a separate, identifiable genus. The species name honours Molly Borthwick, whose support helped the Natural History Museum acquire the specimen.
Is every old small dinosaur now Enigmacursor?
No. Recognising problems with historical names does not automatically transfer every referred fossil to the new genus. Other specimens need to be examined for the characters that actually identify them.
The original analysis recovered Enigmacursor as an early-branching neornithischian outside Cerapoda. That placement describes a relationship hypothesis based on anatomy. It should not be decided by a general resemblance to a small running dinosaur in a picture.
How complete is the skeleton?
The specimen preserves useful portions of the backbone and limbs in three dimensions, but it is not complete. In particular, the skull remains unknown. A finished head in our illustration is therefore an artistic completion rather than a discovered skull.
Some skeletal features suggest that the individual may not have been fully grown. Museum researchers also explain that preparation obscures details relevant to that interpretation. We therefore avoid turning possible immaturity into a definite age or using the specimen as an exact adult size measurement.
Reading the whole-animal view
Our portrait follows a complete reference specifically identified as Enigmacursor. Its small rounded head, short forelimbs, long hindlimbs and straight tapering tail provide the visual framework. Colours, body pattern and soft tissues remain artistic interpretations.
Long legs and a running-related name do not establish a measured speed. Nor does a fossil without an obvious injury reveal its exact cause of death. The engaging reconstruction is paired with sources so that the known skeleton, uncertain growth stage and historical naming puzzle remain clear.
Compare Dryosaurus and Stegosaurus, then explore the E directory.
Quick answers
- Where was Enigmacursor found?
- In the Morrison Formation of Colorado, USA.
- Was its skull found?
- No. The completed head in the image remains an artistic reconstruction.
- Is every fossil once called Nanosaurus now Enigmacursor?
- No. Other specimens require their own anatomical assessment.
- Was the specimen fully grown?
- Some features suggest immaturity, but preparation obscures details, so that interpretation remains qualified.
