Opabinia regalis

Opabinia regalis is an extinct, stem group arthropod found in the Middle Cambrian Burgess Shale Lagerstätte of British Columbia, Canada. It flourished from 505 million years ago to 487 million years ago during the Cambrian Period of the Paleozoic Era. It measured 2-3 inches in length and is presumed to have been a carnivore. Fewer than twenty good specimens have been described; 3 specimens of Opabinia are known from the Greater Phyllopod bed, where they constitute less than 0.1% of the community. Opabinia was a soft-bodied animal, averaging about 5.7 cm in length, and its segmented body had lobes along the sides and a fan-shaped tail. The head shows unusual features: five eyes, a mouth under the head and facing backwards, and a proboscis that probably passed food to the mouth. Opabinia probably lived on the seafloor, using the proboscis to seek out small, soft food.

Charles Doolittle Walcott found in the Burgess Shale nine almost complete fossils of Opabinia regalis and a few of what he classified as Opabinia media, and published a description of all of these in 1912. The generic name is derived from Opabin pass between Mount Hungabee and Mount Biddle, southeast of Lake O'Hara, British Columbia, Canada. In 1966–1967, Harry B. Whittington found another good specimen, and in 1975 he published a detailed description based on very thorough dissection of ...

All the recognized Opabinia specimens found so far come from the "Phyllopod bed" of the Burgess Shale, in the Canadian Rockies of British Columbia. In 1997, Briggs and Nedin reported from South Australia a new specimen of Myoscolex that was much better preserved than previous specimens, leading them to conclude that it was a close relative of Opabinia—although this interpretation was later questioned by Dzik, who instead concluded that Myoscolex was an annelid worm.

Opabinia looked so strange that the audience at the first presentation of Whittington's analysis laughed. The length of Opabinia regalis from head to tail ranged between 4 centimetres and 7 centimetres. The animal also had a hollow proboscis, whose total length was about one-third of the body's and projected down from under the head and then curved forwards and upwards. The proboscis was striated like a vacuum cleaner's hose and probably flexible, and it ended with a claw-like structure whose in.

The way in which the Burgess Shale animals were buried, by a mudslide or a sediment-laden current that acted as a sandstorm, suggests they lived on the surface of the seafloor. Opabinia probably used its proboscis to search the sediment for food particles and pass them to its mouth. Since there is no sign of anything that might function as jaws, its food was presumably small and soft. Whittington, believing that Opabinia had no legs, thought that it crawled on its lobes and that it could also have.