| Diet | Carnivore |
| Environment | Land |
| Era | Triassic |
| Period | Late Triassic |
| Type | Other |
| Location | England |
Avalonianus represents one of palaeontology's most confusing cases - a fossil chimera that has puzzled scientists for over a century. Originally described in 1898 by Harry Seeley as 'Avalonia', this Late Triassic archosaur from England's Westbury Formation was later renamed Avalonianus in 1961 when the original name was found to be already in use.
What makes Avalonianus particularly problematic is that it was based on a mixture of fossils from completely different animals. The original teeth, which are now lost, actually came from an ornithosuchian - a group of crocodile-like archosaurs that were not dinosaurs at all. Later, additional fossil remains from genuine prosauropod dinosaurs were incorrectly attributed to the same genus, creating a confusing jumble of unrelated specimens.
Ornithosuchians like the creature that provided Avalonianus's teeth were fascinating predators that lived during the Late Triassic period, around 208 to 201 million years ago. These archosaurs were part of the diverse ecosystem that existed before dinosaurs became dominant, and they filled similar ecological niches to later carnivorous dinosaurs.
Today, Avalonianus serves as an important reminder of how early palaeontological work sometimes mixed up different species, and why careful analysis of fossil specimens is crucial for understanding prehistoric life.
The original distinguishing features cannot be accurately determined as Avalonianus was based on a mixture of fossils from different animals, and the diagnostic teeth have been lost.
As the original fossil material was a chimera and the teeth are lost, specific behaviours cannot be reliably determined for Avalonianus.
Avalonianus was first described by Harry Seeley in 1898. The original fossils were discovered at Westbury Formation, England.
