Horseshoe Canyon Formation
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The Horseshoe Canyon Formation is part of the Edmonton Series and is up to 230m in thickness. It is Late Campanian to Early Maastrichtian in age (Edmontonian Land Mammal Age) and is composed of mudstone, sandstone, and carbonaceous shales. There are a variety of environments represented by the succession, including floodplains, estuarine channels, and coalswamps, which have yielded a diversity of fossil material. Tidally-influenced estuarine point bar deposits are easily recongizable as Inclined Heterolithic Stratification (IHS). Brackish-water trace fossil assemblages occur within these bar deposits and demonstrate periodic incursion of marine waters into the estuaries. The Horseshoe Canyon Formation crops out extensively in the area of Drumheller, Alberta, as well as further north along the Red Deer River near Trochu, and also in the city of Edmonton. It is overlain by the Battle, Whitemud, and Scollard formations.
Dinosaurs found in the Horseshoe Canyon Formation include Albertosaurus, Anchiceratops, Arrhinoceratops, Atrociraptor, Chirostenotes, Dromiceiomimus, Edmontonia, Edmontosaurus, Euoplocephalus, Hypacrosaurus, Ornithomimus, Pachyrhinosaurus, Parksosaurus, Saurolophus, Stegoceras, Struthiomimus and Troodon. Other finds have included mammals such as Didelphodon coyi, non-dinosaur reptiles, amphibians, fish, marine and terrestrial invertebrates and plant fossils. Reptiles such as turtles and crocodilians are rare in the Horseshoe Canyon Formation, and this is thought to reflect the relatively cool climate which prevailed at the time.
Horseshoe Canyon itself is located 17 km southwest of Drumheller, Alberta, Canada, on Highway 9. This Canyon gets its name from its horseshoe shape and is approximately 3 km long, extending from Highway 9 to Kneehill Creek area.
[edit] Dinosaurs
Theropoda (Currie, 2005)
- Coelurosauria incertae sedis
- Family unknown
- Tyrannosauroidea
- Ornithomimosauria
- Ornithomimidae
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- Dromiceiomimus brevitertius (may be synonymous with Ornithomimus edmontonicus)
- Ornithomimus edmontonicus
- Struthiomimus altus
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- Ornithomimidae
- Maniraptora
Ornithischia (Ryan and Evans, 2005)
- Ankylosauria
- Pachycephalosauria
- Ceratopsia
- Ceratopsidae
- Centrosaurinae
- Chasmosaurinae
- Anchiceratops ornatus
- Arrhinoceratops brachyops
- Eotriceratops xerinsularis‏ (found within the upper 20 m of the formation)
- Ceratopsidae
- Ornithopoda