page_title: Edmontosaurus annectens
section_title: Paleobiology
hierarchical_section_title: Edmontosaurus annectens / Paleobiology
caption_attribution_description: The mandible (lower jaw) of an Edmontosaurus at the Museum of the Rockies in Bozeman, Montana, seen from the inner side (i.e. from the tongue side). It is not clear where this specimen was collected. Edmontosaurs belong to the so-called duck-billed dinosaurs (hadrosaurs), and were exceptionally numerous in Latest Cretaceous times throughout upper North America. As herbivores, they ripped leaves and plants using their bills, and then, unlike reptiles usually do, chewed the leaves and stems extensively. This caused wear to their teeth, which ground down quickly. The teeth were not only lying next to each other but were also stacked one above the other within the jawbone to form vertical tooth rows. So there were quite a lot of teeth in one jaw and all the densely packed teeth together are referred to as ‘tooth battery’. In the jaw that is shown above, many unworn, keeled, diamond-shaped surfaces of the stacked teeth are visible. Furthermore, the teeth erupted in a way that there was more than one tooth functional in each vertical row: The teeth rotated during their lifetime around the long axis of the jaw so that a new tooth first reached the mouth cavity on the inner side of the jaw, yet before the older tooth or teeth, sitting closer to the cheek, were entirely worn down. The tooth wear acting on the surfaces of about one hundred functional teeth formed an inclined chewing surface on each tooth battery. In the image above the chewing or wear surface is not visible because in the mandible it faces toward the cheek, not toward the tongue (but see this image for comparison). Only the inner edge of the chewing surface, running along the top of the inner surface of the tooth battery, with the keels forming conspicious spikes, is discernible.
context_page_description: Edmontosaurus annectens is a species of flat-headed and duck-billed dinosaur from the very end of the Cretaceous Period, in what is now North America. Remains of E. annectens have been preserved in the Frenchman, Hell Creek, and Lance Formations. All of these formations are dated to the late Maastrichtian stage of the Late Cretaceous Period, representing the last three million years before the extinction of the dinosaurs. Also, E. annectens is also from the Laramie Formation, and magnetostratigraphy suggests an age of 69-68 Ma for the Laramie Formation. Edmontosaurus annectens is known from numerous specimens, including at least twenty partial to complete skulls, discovered in the U.S. states of Montana, South Dakota, North Dakota, Wyoming and Colorado and the Canadian province of Saskatchewan. It was a large animal, up to approximately 12 metres, potentially up to 15 m in length, with an extremely long and low skull. E. annectens exhibits one of the most striking examples of the "duckbill" snout common to hadrosaurs.
context_section_description: As hadrosaurids, individuals of Edmontosaurus annectens would have been large herbivores, eating plants with a sophisticated skull that permitted a grinding motion analogous to chewing. Their teeth were continually replaced and packed into dental batteries that contained hundreds of teeth, only a relative handful of which were in use at any time. Plant material would have been cropped by the broad beak, and held in the jaws by a cheek-like structure. Feeding would have been from the ground up to around 4 meters (13 ft) above. Like other hadrosaurs, they could have moved both bipedally and quadrupedally.
  The extensive depressions surrounding its nasal openings may have hosted nasal diverticula. These postulated diverticula would have taken the form of inflatable soft-tissue sacs. Such sacs could be used for both visual and auditory signals.
  A preserved rhamphotheca present in specimen LACM 23502, housed in the Los Angeles County Museum, also indicates the beak of Edmontosaurus was more hook-shaped and extensive than many illustrations in scientific and public media have previously depicted.
caption: Close up of teeth
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