Edmontosaurus annectens

Lore & Background

The history of E. annectens predates the naming of both the genus Edmontosaurus and the species annectens. The first quality specimen, the former holotype of Anatosaurus copei (Anatotitan), was a complete skull and most of a skeleton collected in 1882 by Dr. J. L. Wortman and R. S. Hill for American paleontologist Edward Drinker Cope. This specimen, found in Lance Formation rocks (or equivalent) in South Dakota, came from northeast of the Black Hills, and originally had extensive skin impressions. When describing this specimen, AMNH 5730, Cope assigned it to the species Diclonius mirabilis. Cope's description promoted hadrosaurids as amphibious animals, contributing to this long-time image. Several years after Cope's description, his arch-rival, Othniel Charles Marsh, published a paper on a sizable lower jaw recovered by John Bell Hatcher in 1889 from the Lance Formation rocks in Niobrara County, Wyoming. Marsh named this partial jaw Trachodon longiceps. A second mostly complete skeleton, AMNH 5886, was found in 1904 in the Hell Creek Formation rocks at Crooked Creek in central Montana by a local rancher named Oscar Hunter. In 1908, these two specimens were mounted side by side in the American Museum of Natural History under the name Trachodon mirabilis.

Reader's Guide

Edmontosaurus annectens is significant as one of the most completely known hadrosaurid dinosaurs, with numerous specimens including partial-to-complete skulls and skeletons, some with preserved skin impressions. Its complicated taxonomic history reflects the evolving understanding of hadrosaurid classification in the late 19th and early 20th centuries, with specimens having been assigned to at least seven different genera. The species is among the first dinosaurs to receive a skeletal restoration, and is the first hadrosaurid so restored. Two of its specimens, YPM 2182 and USNM 2414, are respectively the first and second essentially complete mounted dinosaur skeletons in the United States. The "Trachodon mummy" (AMNH 5060), discovered in 1908, preserved extensive skin impressions and a horn-like beak sheath, providing rare insight into the soft tissue anatomy of hadrosaurs. E. annectens also represents one of the last non-avian dinosaur species, living in the final three million years before the Cretaceous–Paleogene extinction event. Its remains have been found across a wide geographic range from Saskatchewan to Colorado, indicating it was a successful and widespread herbivore in the late Maastrichtian ecosystems of western North America.

Did You Know?

• Edmontosaurus annectens is often colloquially and historically known as Anatotitan, meaning 'duck titan'.
• The first quality specimen, AMNH 5730, originally had extensive skin impressions and a horn-like beak sheath with interlocking points.
• Two specimens of E. annectens (YPM 2182 and USNM 2414) are the first and second essentially complete mounted dinosaur skeletons in the United States.
• The species is known from at least twenty partial-to-complete skulls discovered across six U.S. states and one Canadian province.

A Name in Constant Flux

Edmontosaurus annectens carries one of the most tangled naming histories in all of paleontology. Before the species even received its current binomial, its fossils had been shuffled through at least seven different genera across more than a century of research. Cope's 1882 description placed the type specimen under Diclonius mirabilis, a name he constructed by merging his own hadrosaurid genus with an older tooth-based name, Trachodon mirabilis, coined by Joseph Leidy. Marsh, Cope's rival, later erected Claosaurus annectens in 1892 from a partial skull-roof and skeleton. Over the decades, additional specimens were variously assigned to Anatosaurus, Anatotitan, Thespesius, Hadrosaurus, and Trachodon, depending on which author was writing and when. It was not until the 1980s that the taxonomic mess was largely resolved, with all these scattered names folded into Edmontosaurus. The species epithet annectens, meaning "connected," references the type locality near Edmonton, Alberta, while the colloquial nickname Anatotitan—literally "duck titan"—endures in popular usage despite being formally superseded.

Cowboys, Pistols, and Broken Vertebrae

The provenance of Edmontosaurus annectens specimens reads like a frontier novel. In 1882, Dr. J. L. Wortman and R. S. Hill collected a near-complete skull and skeleton from Hell Creek Formation rocks near the Black Hills of South Dakota for Edward Drinker Cope. The specimen still bore extensive skin impressions, though a stream had carved away most of the pelvis and part of the torso. Decades later, in 1904, a Montana rancher named Oscar Hunter stumbled upon a partially exposed skeleton at Crooked Creek in the Hell Creek Formation. Hunter and a companion debated whether the bones were recent or fossil; Hunter settled the argument by kicking the tops off exposed vertebrae, proving their brittleness and stony nature—an act that later collector Barnum Brown would lament. A cowboy named Alfred Sensiba purchased the find from Hunter for a single pistol, then resold it to Brown, who excavated it for the American Museum of Natural History in 1906. That specimen, catalogued as AMNH 5886, preserved a nearly complete vertebral column and proved essential for reconstructing Cope's more fragmentary original.

The Duckbill That Defined a Dinosaur

Edmontosaurus annectens is one of the most visually distinctive hadrosaurids ever described, owing largely to its extraordinarily long, low skull and the pronounced "duckbill" snout that gave the entire hadrosaur family its popular name. The species reached roughly twelve metres in total length and averaged about 5.6 metric tons in body mass, though some individuals may have exceeded even that. Cope's original 1882 specimen revealed a bill that bore impressions of a horn-like sheath, its upper and lower jaws lined with a tooth-like series of interlocking points—a feature that would later inform debates about feeding mechanics. Cope himself had interpreted the weakly attached lower-jaw teeth and the beak's apparent fragility as evidence that hadrosaurids were amphibious creatures, a misconception that persisted for generations. In reality, the lower jaws in that particular specimen had lost the internal bony walls that normally brace the teeth, making them appear far more delicate than they truly were. The animal's flat-headed, saurolophine skull architecture, combined with its sheer size, made it one of the most recognizable large herbivores of the final three million years before the non-avian dinosaur extinction.

A Dramatic Tableau at the American Museum

The rivalry between Edward Drinker Cope and Othniel Charles Marsh cast a long shadow over Edmontosaurus annectens research. Marsh published a partial lower jaw, YPM 616, recovered by John Bell Hatcher in 1889 from Lance Formation rocks in Niobrara County, Wyoming, naming it Trachodon longiceps. That dentary measured roughly 110 centimetres—nearly eighteen centimetres longer than the 92-centimetre dentary in Cope's earlier specimen—underscoring just how much variation existed within the species. In 1908, the American Museum of Natural History mounted Cope's AMNH 5730 and Brown's AMNH 5886 side by side under the name Trachodon mirabilis. Henry Fairfield Osborn staged the display as a narrative scene: the quadrupedal specimen, with its superior skull, was posed head-down as if grazing, while the bipedal individual appeared startled by the approach of a Tyrannosaurus. The base of the mount was decorated with impressions of ginkgo leaves, Sequoia cones, and horsetail rushes drawn from associated fossils, transforming a taxonomic exhibit into a vivid snapshot of Late Cretaceous life.