Featured Article Summary #227

The Edmontosaurus mummy SMF R 4036, also known as the Senckenberg mummy or “Edmond,” is a very well-preserved dinosaur fossil in the Senckenberg Museum in Frankfurt, Germany. It was discovered in 1910 in Wyoming, USA, in late Maastrichtian rocks of the Lance Formation, close to the time of the Cretaceous–Paleogene extinction about 66 million years ago. The fossil belongs to the hadrosaur species Edmontosaurus annectens and includes an almost complete skeleton with skin impressions—an unusually rare kind of preservation—plus a horny beak. Plant remains found inside the body cavity were once thought to be stomach contents, suggesting a plant diet, but are now believed to have been washed in after death. Scientists think the dinosaur may have died during a drought near a river, dried out, and then was quickly buried after a sudden flood; sand and a bacterial film helped preserve the body shape and skin details. The mummy was found by Charles H. Sternberg and his sons and is among the best-preserved hadrosaurid mummies, being the second discovered in the region after an earlier find by the Sternbergs. The Sternberg family, commercial fossil hunters, discovered the mummy in early September 1910 near what is now Snyder Creek in Wyoming while working in the Lance Formation. They had previously found similar and related fossils in the same region, and the mummy was recovered in an especially large, careful transport effort, arriving at the Senckenberg Museum in 1911 and being prepared from 1912 until about 1920 using newer compressed-air tools. After later studies were limited for decades, the mummy was protected during World War II but was damaged in an accident and took over 10 years to restore; since 2018, the museum’s Edmontosaurus project has renewed research, including re-checking supposed stomach contents and rebuilding the ancient environment. The Senckenberg specimen is the second dinosaur mummy ever discovered. The idea of “dinosaur mummies” was first used in 1911 for an Edmontosaurus mummy, and more similar hadrosaurid specimens were found in North America, including one sent to London in 1916 that was lost when the ship carrying it was sunk. The mummy belongs to Edmontosaurus annectens in the hadrosauridae family, though it was previously classified as Trachodon and later Anatosaurus before being reassigned to Edmontosaurus. Hadrosaurids are where most dinosaur skin impressions are found, and about 25% of all known hadrosaurid skin impressions belong to Edmontosaurus. The mummy skeleton is mostly complete, missing one hind limb and the end of the tail, but it is more complete than another known specimen. The skull is very well preserved, including the horny beak impression and the eye’s scleral ring, and measurements suggest it belonged to an old adult about 122% the size of the earlier specimen. The bones remain in their original positions and are mostly three-dimensional, with preserved skin impressions on the right trunk and neck and around both forearms, especially detailed around the right hand where small polygonal scales are visible. Both the AMNH and Senckenberg hadrosaur mummies show finger impressions enclosed like a mitten, which led early researchers to think hadrosaurids lived in water, using webbing and paddle-like forelimbs. Later studies challenged this idea: Ostrom argued they fed on land plants and were built for walking, and Bakker suggested the “webbing” was just dried fleshy tissue from the hand. The preserved hind-limb posture first suggested a low, sprawled stance, but later work showed that these dinosaurs had erect limbs and held their bodies and tails off the ground.