Pronunciation: ARK-to-SOR-us
Meaning: Arctic lizard
Author/s: Adams (1875)
Synonyms: None known
First Discovery: Nunavut, Canada
Discovery Chart Position: #
Arctosaurus osborni
Based, as it is, on a single partial neck bone, it's surprising that paleontologists have spent so much time fiddling with Arctosaurus. It was originally described as "a reptile of unknown affinities" (Adams 1875) and later tagged an anchisaurid sauropodomorph (Lydekker 1889), a turtle (Huene 1906), a melanorosaurid (Huene 1956), and a thecodontosaurid (Romer 1966). Then Galton and Cluver (1976) granted it entry into Theropoda on the grounds of weight-saving openings in the sides of its vertebra — a feature known to boffins as "pleurocoels".
The term "pleurocoel" has been redefined in recent times, and in a critical review of Triassic dinosaurs in 2007 Sterling Nesbitt showed that Arctosaurus didn't have 'em. So this troublesome critter, once reported as "the first dinosaur ever described from Canada", fell a little short of its own headline by not actually being a dinosaur and only scrapes into Archosauriformes because there isn't enough evidence to move it anywhere else. But on the plus side, it is the northernmost occurrence of a Late Triassic land-dwelling tetrapod discovered to date.
The term "pleurocoel" has been redefined in recent times, and in a critical review of Triassic dinosaurs in 2007 Sterling Nesbitt showed that Arctosaurus didn't have 'em. So this troublesome critter, once reported as "the first dinosaur ever described from Canada", fell a little short of its own headline by not actually being a dinosaur and only scrapes into Archosauriformes because there isn't enough evidence to move it anywhere else. But on the plus side, it is the northernmost occurrence of a Late Triassic land-dwelling tetrapod discovered to date.
(Osborn's Arctic Lizard)Etymology
Arctosaurus is derived from "Arctic" (its place of discovery) and the Greek "sauros" (lizard). The species epithet, osborni, honours Sherard Osborn who discovered the specimen.
Discovery
Arctosaurus was discovered in the Heiberg Formation (Bathurst Group) on Cameron Island, Nunavut, Arctic Archipelago, Canada, by Admiral Sherrard Osborn.The holotype (NMI 62 1971) is a partial neck (cervical) vertebra.
