Edmontosaurus

Edmontosaurus is among the largest and most extensively studied hadrosaurids. Paleontologists recognise two species today: the older E. regalis from the late Campanian and the younger E. annectens from the Maastrichtian. E. regalis is notable for possessing a soft-tissue "cock's comb" on its head, while E. annectens was the primary hadrosaur in the Hell Creek ecosystem. In the past, the genus served as a taxonomic "wastebasket" for various species now consolidated under Edmontosaurus, including those once known as Anatosaurus, Anatotitan, Trachodon, and Diclonius.

These large, broad-snouted herbivores had flat-topped skulls lacking the bony crests of lambeosaurines like Parasaurolophus. They possessed some of the most advanced dental systems of any dinosaur, with more than 1,000 teeth arranged in columns. These batteries were constantly replaced and formed a powerful grinding surface for tough plants. The animal's body was robust, capable of both two-legged and four-legged movement. Several specimens include skin impressions that show small polygonal scales and rows of larger plates along the spine.

A 2013 study by Bell et al. revealed a fleshy cranial comb on a specimen of E. regalis. This structure, similar to a rooster's comb, was likely used for sexual display. Because it was made of soft tissue, it is not preserved in the vast majority of skeletons.

Edmontosaurus was a generalist herbivore that lived in herds across the Late Cretaceous landscapes of Laramidia and Alaska. Large-scale fossil sites, such as the Liscomb Bonebed in northern Alaska and various Hell Creek localities, contain thousands of individuals, which strongly suggests mass herding behaviour. One of the most famous examples of dinosaur interaction is an Edmontosaurus annectens tail with a healed T. rex bite mark. This fossil, cited by Carpenter (1998) and DePalma et al., confirms that T. rex engaged in active hunting and that Edmontosaurus could sometimes survive such encounters.

Analysis of tooth wear shows that these dinosaurs processed fibrous plants including conifers, ferns, and early flowering plants. The abundance of fossils, including growth series, has allowed for a detailed reconstruction of their life history.

• AMNH 5060 — the famous "Trachodon mummy," American Museum of Natural History; preserves skin impressions over much of the body.
• CMN 8399 ("Edmontosaurus regalis with cock's comb") — Royal Tyrrell Museum; basis for soft-tissue crest description.
• Liscomb Bonebed material — University of Alaska, Prince Creek Formation.
• MOR 1142 — T. rex bite-marked specimen, Museum of the Rockies.

Anatotitan / Edmontosaurus annectens synonymy — most workers now treat Anatotitan as a junior synonym of E. annectens, but some retain the distinction. Cock's comb extent — known from E. regalis, presumed for E. annectens but not directly preserved. Mass estimates — typical adults ~4 tonnes, largest individuals ~9 tonnes. Migration — Alaskan populations may have migrated seasonally or been resident; debate ongoing.

Edmontosaurus appears in Walking with Dinosaurs (1999), Prehistoric Planet (2022), and many recent dinosaur films. The "Trachodon mummy" is one of the most-photographed dinosaur fossils in the AMNH.

• ornithopoda
• parasaurolophus
• lambeosaurus
• hadrosaurus
• tyrannosaurus-rex

• Bell, P. R., Fanti, F., Currie, P. J., & Arbour, V. M. (2014). A mummified duck-billed dinosaur with a soft-tissue cock's comb. Current Biology, 24, 70–75.
• Campione, N. E., & Evans, D. C. (2011). Cranial growth and variation in Edmontosaurus and the systematics of edmontosaurine hadrosaurids. PLOS ONE, 6, e25186.
• Carpenter, K. (1998). Evidence of predatory behavior by carnivorous dinosaurs. Gaia, 15, 135–144.
• Horner, J. R., Weishampel, D. B., & Forster, C. A. (2004). Hadrosauridae. In The Dinosauria (2nd ed.).