Edmontosaurus, the duck-billed giant that grazed beside Tyrannosaurus until the asteroid
One of the very last non-avian dinosaurs was a flat-snouted plant eater up to 12 metres long. Edmontosaurus roamed from Colorado to Alaska's north slope in herds, shared its world with Triceratops and Tyrannosaurus, and some of its bones even carry marks from tyrannosaur attacks.
The genus holds two species. Edmontosaurus regalis turns up in western North American rocks about 73 million years old, while E. annectens lived right at the end of the Cretaceous, 66 million years ago, just before the mass extinction. Typical annectens adults reached 12 metres and around 5.6 tonnes, and exceptional individuals may have hit 15 metres and nearly 16 tonnes, placing them among the biggest hadrosaurs known. Unlike crested relatives with hollow head ornaments, it had at most a small solid crest or fleshy comb.
It walked on two legs or four, preferred coasts and coastal plains, and its mass bone beds suggest it lived in groups and perhaps migrated. Specimens are so plentiful and well preserved, some with skin impressions and possible stomach contents, that researchers have studied its brain, feeding and injuries in detail. In 2025 Tuinstra and colleagues detected hydroxyproline, a building block of collagen, in an Edmontosaurus fossil, the first clear identification of genuine original dinosaur organic material and a blow to the idea that such traces must be contamination.
The name, meaning lizard from Edmonton, came from Lawrence Lambe in 1917, based on finds in southern Alberta's Horseshoe Canyon Formation. Yet annectens had been described 25 years earlier by Othniel Charles Marsh, as a species of Claosaurus, from two skeletons John Bell Hatcher dug up in Wyoming in 1891. Those became the first hadrosaur ever given a skeletal restoration and the first two essentially complete dinosaur skeletons mounted in the United States, displayed in 1901 and 1904.
Then came decades of reshuffling. After Marsh died in 1897 the species was bounced between Claosaurus, Thespesius and Trachodon, and Hatcher in 1902 lumped almost every known duckbill into Trachodon until new Canadian and Montana finds exposed more variety. Charles Gilmore reshuffled things again in 1915. Popular books long called the animal Anatosaurus or Anatotitan, duck lizard and giant duck, names now treated as synonyms.
Source: Edmontosaurus
