Description and Classification

Edmontosaurus was a large dinosaur, typically reaching lengths of 9 to 13 meters (about 30 to 43 feet) and weighing several tons, possibly around 4 to 7 metric tons. Its most recognizable feature was its wide, flattened snout, similar to a duck’s bill, which was toothless at the front. However, further back in its jaws, Edmontosaurus possessed hundreds of tightly packed teeth, forming complex “dental batteries.” These were incredibly effective for grinding tough plant material. It could walk on its two strong hind legs (bipedally) or on all fours (quadrupedally), using its front limbs for support when feeding low to the ground. Unlike some other hadrosaurs like Parasaurolophus, Edmontosaurus did not have a large, hollow bony crest on its head, although some specimens of E. regalis suggest it may have had a fleshy comb or frill. Fossilized skin impressions show that its body was covered in scales of different sizes.

Edmontosaurus belongs to the order Ornithischia (bird-hipped dinosaurs) and the family Hadrosauridae, commonly known as duck-billed dinosaurs. Within this family, it is classified in the subfamily Saurolophinae (sometimes called Hadrosaurinae). Saurolophines are generally characterized by their lack of hollow, elaborate cranial crests, distinguishing them from the Lambeosaurinae subfamily, which includes dinosaurs like Corythosaurus and Lambeosaurus. Other relatives within the hadrosaur group include dinosaurs such as Maiasaura and Saurolophus.

Distinguishing Features

• A broad, flattened, duck-like beak (rostrum) at the front of its snout, which was toothless.
• Complex dental batteries located in the cheeks, containing hundreds of constantly replaced teeth designed for grinding vegetation.
• The absence of large, hollow bony crests on its skull, though some evidence points to soft-tissue structures like a fleshy comb or frill on the head of certain species (e.g., E. regalis).
• A robust body capable of both bipedal (two-legged) movement for running and quadrupedal (four-legged) posture for walking or grazing.
• A long, stiff, and heavy tail that provided balance, especially when moving bipedally or standing.
• Well-preserved skin impressions revealing a covering of non-overlapping scales, some small and uniform, others larger and polygonal.

Paleoenvironment and Diet

Edmontosaurus lived in the coastal plains, river valleys, and swampy lowlands of western North America during the final stages of the Cretaceous period. Its fossils are commonly found in well-known geological formations such as the Hell Creek Formation and Lance Formation in the United States, and the Horseshoe Canyon Formation and Scollard Formation in Canada. These environments were warm and humid, with abundant forests, wetlands, and rivers. Edmontosaurus shared these habitats with a diverse range of other dinosaurs, including the formidable predator Tyrannosaurus rex (which is known to have preyed on Edmontosaurus), horned dinosaurs like Triceratops, armored ankylosaurs like Ankylosaurus, and various smaller dinosaurs and other animals.

As a hadrosaurid, Edmontosaurus was a herbivore. Its specialized duck-bill was likely used for cropping leaves and twigs from plants, while its powerful dental batteries were perfect for grinding tough vegetation. Studies of fossilized stomach contents (cololites) and patterns of tooth wear suggest that Edmontosaurus consumed a diet rich in conifers (like pine needles and twigs), cycads, ferns, and early flowering plants. It was likely a versatile feeder, browsing on vegetation at various heights from the ground up to about 4 meters (13 feet).

Significance and Ongoing Research

Edmontosaurus is one of the most well-understood hadrosaurs, thanks to the discovery of numerous fossils, including many complete or nearly complete skeletons. Exceptionally preserved specimens, sometimes referred to as “dinosaur mummies,” have even retained skin impressions and, in some cases, other soft tissues like keratinous beak sheaths or possible traces of internal organs. These finds provide invaluable information about hadrosaur anatomy, appearance, and biology. The abundance of Edmontosaurus fossils also helps paleontologists understand dinosaur herd structures and population dynamics. Furthermore, bite marks and healed injuries found on Edmontosaurus bones, some matching the teeth of Tyrannosaurus rex, offer direct evidence of predator-prey interactions in Late Cretaceous ecosystems.

Ongoing research continues to expand our knowledge of Edmontosaurus. Scientists are studying “mummy” specimens in greater detail using advanced imaging techniques to learn more about its soft-tissue anatomy, such as the structure of its skin and the nature of any head ornamentation. Studies on bone histology (the microscopic structure of bone) help determine growth rates and how long these dinosaurs lived. Biomechanical analyses focus on how Edmontosaurus moved and fed. The discovery of large bonebeds suggests that Edmontosaurus may have lived in large herds, and researchers investigate these sites for clues about social behavior and possible migration patterns. The classification of different species within Edmontosaurus, particularly the relationship between E. annectens and forms previously called Anatosaurus or Anatotitan, also remains an area of active study and discussion among paleontologists.