| Diet | Herbivore |
| Height | 1m |
| Length | 3m |
| Weight | 50 kg |
| Environment | Land |
| Era | Cretaceous |
| Period | Late Cretaceous |
| Type | Ornithopod |
| Location | Europe |
Onychosaurus was a small ornithopod dinosaur that lived during the Late Cretaceous period, between 83.6 and 72.2 million years ago in what is now Romania. However, this dinosaur remains one of palaeontology's more mysterious creatures, as it is known only from very fragmentary fossil remains that make it difficult to study in detail.
The fragmentary nature of Onychosaurus fossils means that much about its appearance and behaviour remains uncertain. What we can infer is that it was likely a small, plant-eating ornithopod that walked on two legs, similar to other small herbivorous dinosaurs of its time. It would have inhabited the ancient landscapes of Transylvania during the final phase of the Cretaceous period, when this region was a collection of islands in a warm, tropical sea.
As an ornithopod, Onychosaurus would have possessed the characteristic beak-like front of the mouth for cropping vegetation, along with cheek teeth adapted for processing plant material. The name 'Claw Lizard' suggests that distinctive claws were amongst the fossil remains discovered, though the incomplete nature of the specimens makes it challenging to determine exactly how these claws were used.
Like many dinosaur discoveries from the early 20th century, Onychosaurus represents the challenges faced by palaeontologists working with limited fossil evidence, highlighting how much we still have to learn about the diversity of dinosaur life during the Cretaceous period.
The distinguishing features of Onychosaurus remain largely unknown due to the fragmentary nature of its fossil remains. The notable claws that gave this dinosaur its name appear to have been distinctive enough to warrant mention in its original description.
The behaviour of Onychosaurus is largely speculative due to the limited fossil evidence. As a probable small ornithopod, it would likely have been a herbivore that moved on two legs and possibly lived in small groups, feeding on the low-growing vegetation of Late Cretaceous Romania.
Onychosaurus was first described by Franz Nopcsa in 1902. The original fossils were discovered at Transylvania, Romania.
