Earth:Edmontosaurus mummy S.M. R4036

The Senckenberg mummy

The Edmontosaurus mummy S.M. R4036 is an exceptionally well-preserved dinosaur fossil in the collection of the Naturmuseum Senckenberg (S.M.) in Frankfurt am Main, Germany. Found in 1910 in Wyoming, United States, it is ascribed to the species Edmontosaurus annectens, a member of the Hadrosauridae ("duckbilled dinosaur"). The fossil comprises a complete skeleton that was found wrapped in impressions of its skin, a rare case of exceptional preservation for which the term "dinosaur mummy" has been used. S.M. R4036 is one of the four best preserved hadrosaur mummies, and was the second to be discovered. The find was made by the Sternberg family, a famous family of fossil hunters who sold their numerous finds to various museums in North America and Europe. Only two years earlier the Sternbergs had discovered the famous Edmontosaurus mummy AMNH 5060 in the same region, which is now on display at the American Museum of Natural History in New York City .

History of discovery

The mummy was discovered in the summer of 1910 by the Sternberg family in rocks of the Lance Formation in Converse County (today Niobrara County). The Sternbergs – Charles Hazelius Sternberg as well as his three sons Charles Mortram, George and Levi – had worked in this area since 1908. In 1908 and 1909 the family had discovered the famous Trachodon mummy and two skulls of the horned dinosaur Triceratops in the Lance; one skull was sold to the British Museum of Natural History in London, while the other skull as well as the famous Edmontosaurus mummy AMNH 5060 was acquired by the American Museum of Natural History in New York City.

The mummy comes from the southern Schneider Creek area. Charles Mortam discovered parts of a tail weathering out of the sandstone as he roamed the area in search for fossils. The subsequent erosion of the sandstone resting on the fossil revealed a complete skeleton with skin impressions. As Charles Hazelius reports, the skeleton measured 5.25 metres in length when found, with the skull accounting for 1.2 metres, the torso for 2.4 metres, and the tail 1.65 metres. The recovery of the fossil was the most elaborate the family had ever undertaken. Charles Hazelius was determined to secure every fragment of the skin impressions, which is why the blocks packed for transport were particularly large: the block containing the mummy's trunk weighed about 1.6 tons, while the entire fossil weighed about 4.5 tons. Since the Sternbergs had no pulley, the block was lifted step by step, by elevating it using levers of poplar wood and subsequently shovelling sand underneath. When the block was lifted to a height of 1.2 meters, it could be loaded onto a wagon for transportation to the railway station 120 kilometers away in Edgemont, South Dakota. The excavation and transport took two and a half months to complete.

Charles Hazelius offered the fossil Fritz Drevermann, palaeontologist and director of the Naturmuseum Senckenberg, for sale. Drevermann was able to pay the required sum of money thanks to a donation from the industrialist Arthur von Weinberg. Shortly after Drevermann's commitment, Sternberg received an offer from the Canadian Museum of Nature in Ottawa. The museum offered twice the amount of money for the fossil, including assembly, than Sternberg was to receive from the Senckenberg Museum without assembly. Sternberg wrote in 1917:

I shall never forget the effort I made to induce him to give up the specimen, or take another in its stead. [...] But it crossed the Atlantic. The last message I had of it, before this awful war cut off all communications, was that the head had been prepared and it was the best of which there was any record.

In the summer of 1910 the Sternbergs also discovered four Triceratops skulls in the Lance, two of which were also acquired by the Senckenberg Museum.

Description

The mummy shows a similar degree of preservation to that of the AMNH 5060 mummy of the American Museum. Its skeleton is almost completely preserved, while the AMNH mummy misses the tail, hind feet, and part of the pelvis. In a number of other respects, however, the Senckenberg mummy is less well preserved than the AMNH mummy. As with the latter, the bones are fully articulated (still in their original anatomical position) and mostly preserved three-dimensionally, not flattened as with many other fossils. Skin impressions are preserved from the right side of the trunk and the neck as well as from both forearms. Especially well preserved impressions were found on the hands, these impressions show scales of 3 to 5 millimeters in diameter. Most of the skin impressions had been separated from the skeleton during preparation.

Taphonomy

The AMNH 5060 mummy, which was discovered in the same area, is commonly interpreted as the fossil of a natural mummy that formed by dehydration of the carcass. This is indicated by the close adherence of the skin impressions to the bones, and the fact that they are partially drawn into the body cavity. The Sternbergs noted that the preservation of the Senckenberg mummy differed: the skin would not adhere closely to the bone, but rather trace the original body contour. This indicates that the carcass did not dry out before burial. In addition, the Senckenberg mummy was not preserved in a supine position like the Trachodon mummy, but in an upright position, with the tip of the muzzle pointing upwards and the legs pressed against the body. The Sternbergs suggested that the animal sank into soft sediment, possibly quicksand, and subsequently suffocated; the peculiar position of the specimen would have been the animal's death pose as it struggled to escape. Phil Manning stated in 2008 that the quick sand hypothesis cannot be confirmed by sediment samples of the site of discovery. The animal probably got buried very rapidly, however, resulting in its high degree of preservation.

In contrast, employees of the Senckenberg Museum wrote that the mummy is probably the fossil of a natural dry mummy, as it was suggested for the AMNH mummy. This would be indicated by the cramped body posture with the neck bent backwards.