partial skull fmnh p15003 in field museum
the horseshoe canyon formation has been radiometrically dated being between 74 , 67 million years old. deposited during gradual withdrawal of western interior seaway, during campanian , maastrichtian stage of late cretaceous period. horseshoe canyon formation terrestrial unit part of edmonton group includes battle formation , whitemud member, both in edmonton. valley dinosaurs lived included ancient meandering estuary channels, straight channels, peat swamps, river deltas, floodplains, shorelines , wetlands. due changing sea levels, many different environments represented in horseshoe canyon formation, including offshore , near-shore marine habitats , coastal habitats lagoons, , tidal flats. area wet , warm temperate subtropical climate. prior campanian–maastrichtian boundary, mean annual temperature , precipitation in region dropped rapidly. dinosaurs formation form part of edmontonian land vertebrate age, , distinct in formations above , below.
anchiceratops specimens found in upper part of unit 1 of formation, part of horsetheif member, dated 72-71 million years ago. anchiceratops shared paleoenvironment other dinosaurs, such maniraptorans (epichirostenotes curriei), ornithomimids (ornithomimus edmontonicus), pachycephalosaurids (sphaerotholus edmontonensis), hadrosaurids (edmontosaurus regalis), ceratopsians (pachyrhinosaurus canadensis), , unidentified tyrannosaurids, apex predators. of these, hadrosaurs dominated in terms of sheer number , made half of dinosaurs lived in region. other vertebrates present in horseshoe canyon formation @ time of anchiceratops included reptiles, , amphibians. sharks, rays, sturgeons, bowfins, gars , gar-like aspidorhynchus made fish fauna. reptiles such turtles , crocodilians rare in horseshoe canyon formation, , thought reflect relatively cool climate prevailed @ time. study quinney et al. (2013) however, showed decline in turtle diversity, attributed climate, coincided instead changes in soil drainage conditions, , limited aridity, landscape instability, , migratory barriers. saltwater plesiosaur leurospondylus present , freshwater environments populated turtles, champsosaurus, , crocodilians leidyosuchus , stangerochampsa. evidence has shown multituberculates , marsupial didelphodon coyi present. vertebrate trace fossils region included tracks of theropods, ceratopsians , ornithopods, provide evidence these animals present. non-vertebrates in ecosystem included both marine , terrestrial invertebrates.
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