Dinosaur mummies

The Trachodon mummy is a very well-preserved fossil of Edmontosaurus annectens, a duckbilled dinosaur. It was found by Charles Hazelius Sternberg and his three sons near Lusk, Wyoming, USA in 1908. Although Sternberg was working under contract to the British Museum of Natural History, Henry Fairfield Osborn of the American Museum of Natural History managed to secure the mummy for $2,000.

The mummy
The mummy was found lying on its back with its head pulled under its body, while its right arm stuck out into the air. The skin of the chest and abdominal region was pulled into the body cavity, and the tail, hind feet, and hind portion of the pelvis had eroded away. The hands of the Edmontosaurus and other species unearthed later suggested the presence of webbed feet, but was later found to be inconsistent with footprint evidence. It has since then been proposed that hadrosaur forefeet have a hard, horseshoe-shaped pad. The webbed skin was later found to be from the postmortem displacement of loose skin of the hand.

Osborn's description
In 1912, Osborn came up with a description of the fossil and a theory to its mummification:

"After a natural death (in other words, not death by predators) the body lay exposed to the sun for a long time, perhaps on a sand bar or in a stream. The muscles and soft internal tissues became completely dried and shrunken while the skin, hardened and leathery, shrank around the limbs and was drawn down along the bones. In the stomach and abdominal areas the skin was drawn within the body cavity, while along the sides of the body and on the arms, it was formed into creases and folds. At some later date, the "mummy" may have been caught in a sudden flood and carried downstream and rapidly buried in fine sand and clay. A cast, or impression, of the skin formed in the sand before the skin and other soft parts decayed. There is no remnant of the actual skin preserved only its imprint."

AMNH 5060, the "Trachodon mummy" (so-called because it appears to be a fossil of a natural mummy), is now recognized as a specimen of E. annectens. It was found to have skin impressions over the snout, much of the neck and torso, and parts of the arms and legs. The tail and part of the legs eroded before collection, so these areas are unknown for the specimen. Additionally, some areas with skin impressions, such as sections associated with the neck ridge (see below) and hands, were accidentally removed during preparation of the specimen. The specimen is thought to have desiccated in a dry stream bed, probably on or near a point bar. The circumstances of the location and preservation of the body suggest that the animal died during a prolonged drought, perhaps from starvation. The desiccated carcass was eventually buried in a sudden flood, surrounded by sediment that had enough fine particles to make a cast of the epidermal structures. The epidermis was thin, and the scalation composed of small nonoverlapping scales, as seen in the Gila monster. Two general types of scales were present over most of the body: small pointed or convex tubercles, 1 to 3 mm in diameter with no definite arrangement (ground tubercles); and larger, flat polygonal tubercles (pavement tubercles) typically less than 5 mm in diameter, but up to 10 mm over the forearm. The pavement tubercles were grouped into clusters separated by ground tubercles, with transitional scales between the two types. Over most of the body, the pavement tubercles were arranged in circular or oval clusters, while near the shoulder on the upper arm, they formed strips roughly parallel to each other and the shoulder blade. Generally, clusters were larger on the upper surfaces of the body and smaller on the underside. Clusters up to 50 cm in length were present above the hips.

The only impressions from the head came from the large opening for the nostrils. Instead of tubercle impressions, there were impressions of folded soft tissue, with a deeper area at the anterior end of the opening that may have been the approximate location of the nostril itself. The neck and back had a soft ridge or frill running down the midline, with a row of oval tubercle clusters arranged above the spines of the vertebrae. The total height of the ridge on AMNH 5060 is not known, nor the disposition of its upper border, as the upper extremity was prepared away. The ridge was at least 8 cm tall, and was folded and creased to permit movement. Osborn proposed that it was tall enough for another row of clusters.

The forearms had the largest tubercles, arranged in single large clusters that covered the leading surfaces. The hands were covered in small pavement tubercles in a soft-tissue structure than enclosed the three central fingers; not even the tips were exposed. Osborn interpreted this as a paddle for swimming. Robert T. Bakker later reinterpreted it as a soft-tissue pad for walking, analogous to that of a camel. Like the forearm, the shin had large tubercles. The scalation of the rest of the leg is not presently known, although impressions on a specimen of the crested hadrosaurid Lambeosaurus suggest that the thighs were under the skin of the body, like modern birds.

The tail of AMNH 5060 was not present, but other specimens have filled in some details for that area. Skin impressions from a partial tail belonging to either Edmontosaurus or its close relative Anatotitan, recovered from the Hell Creek Formation of Montana, show a segmented ridge above the vertebrae. The ridge was about 8.0 cm tall, with the segments being about 5.0 cm long and 4.5 cm high, spaced 1.0 cm apart, with one segment to a vertebra. Another tail, this time pertaining to a juvenile E. annectens, had fossilized impressions including tubercles as well as previously unseen skin textures. These impressions included elliptical overlapping scales, grooved scales, and a "9 cm by 10 cm trapezoidal horn-like structure".

The Senckenberg mummy
During this time frame (1902–1915), two additional important specimens of C. annectens were recovered. The first, the "Trachodon mummy" (AMNH 5060), was discovered in 1908 by Charles Hazelius Sternberg and his sons in Lance Formation rocks near Lusk, Wyoming. Sternberg was working for the British Museum of Natural History, but Henry Fairfield Osborn of the American Museum of Natural History was able to purchase the specimen for $2,000. The Sternbergs recovered a second similar specimen from the same area in 1910, not as well preserved but also found with skin impressions. They sold this specimen (SM 4036) to the Senckenberg Museum in Germany.

Both of the "mummy" specimens collected by the Sternbergs were reported to have had possible gut contents. Charles H. Sternberg reported the presence of carbonized gut contents in the American Museum of Natural History specimen, but this material has not been described. The plant remains in the Senckenberg Museum specimen have been described, but have proven difficult to interpret. The plants found in the carcass included needles of the conifer Cunninghamites elegans, twigs from conifer and broadleaf trees, and numerous small seeds or fruits. Upon their description in 1922, they were the subject of a debate in the German-language journal Paläontologische Zeitschrift. Kräusel, who described the material, interpreted it as the gut contents of the animal, while Abel could not rule out that the plants had been washed into the carcass after death. At the time, hadrosaurids were thought to have been aquatic animals, and Kräusel made a point of stating that the specimen did not rule out hadrosaurids eating water plants. The discovery of possible gut contents made little impact in English-speaking circles, except for another brief mention of the aquatic-terrestrial dichotomy, until it was brought up by John Ostrom in the course of an article reassessing the old interpretation of hadrosaurids as water-bound. Instead of trying to adapt the discovery to the aquatic model, he used it as a line of evidence that hadrosaurids were terrestrial herbivores.

The lost Mount Temple mummy
In 1916, the Canadian (Canadian Pacific Lines) ship Mount Temple was carrying two specimens and other fossils from today's Dinosaur Provincial Park, Alberta, Canada to Britain. It was sunk by the German surface raider SMS Moewe, sending its 75 million year old cargo to the bottom of the North Atlantic, where it rests to this day.

"Leonardo"
In 1994, amateur paleontologist Nate Murphy discovered an immaculate, complete and uncrushed brachylophosaur skeleton which he nicknamed 'Elvis'. More impressive finds lay ahead for Murphy and his team from the Judith River Dinosaur Institute. In 2000, 'Leonardo', a fully articulated and partially mummified skeleton of a subadult brachylophosaur, was discovered. It is considered one of the most spectacular dinosaur finds ever, and was included in the Guinness Book of World Records.

"Dakota"
In 2007 another "mummy" was announced; nicknamed "Dakota", it was discovered in 1999 by Tyler Lyson, and came from the Hell Creek Formation of North Dakota.

Dakota is the nickname given to a fossil Edmontosaurus from the Hell Creek Formation in North Dakota. It is about 67 million years old, placing it in the Maastrichtian, the last stage of the Cretaceous period. It was about 11 m (35 ft) long and weighed about 3.5 tons.

The fossil is unusual and scientifically valuable because soft tissue including skin and muscle have been fossilized, giving researchers the rare opportunity to study more than bones, as with most vertebrate fossils. Preliminary research results indicate that hadrosaurs had heavier tails and were able to run faster than was previously thought.

Preservation
Dinosaur fossils with Dakota's degree of preservation are extremely rare because many different factors must come together to allow it to occur. The carcass first must escape scavengers as well as degradation by the elements. The soft tissue must then be mineralized before it decomposes. Finally, as with all fossils, the mineralized body must escape destruction by geological forces over millions of years.

News reports have referred to Dakota as "mummified"; however, it is actually a fossil of a mummified dinosaur, where the animal's dried tissues have been transformed to rock through fossilization.

Discovery and analysis
Dakota was first discovered by paleontology student Tyler Lyson on his family's North Dakota property in 1999 while he was a high school student, but he did not investigate the site in detail until 2004, when he discovered the soft tissue preservation. Lyson teamed with British paleontologist Phillip Manning, and the site was excavated in summer 2006.

Manning's team used a large-scale CT scanner, provided by NASA and the Boeing Company, to generate high-resolution scans of the preserved muscles and tendons of the rear legs. Because the intervertebral discs which space out the spinal column of the tail have been fossilized, researchers have been able more accurately to calculate its length. The preservation of its muscles and tendons allow the calculation of its mass. The results indicate the dinosaur could likely have run at 45 km/h (28 mph), faster than the estimated top speed of Tyrannosaurus rex, at 32 km/h (20 mph).

The well-preserved integument has retained its texture, and researchers have mapped it in three dimensions. The scales are of different sizes, and researchers speculate that their pattern may reflect the animal's coloration in life. For example, areas of an arm's joints are textured in what resembles a striped pattern.

Sources and external links

 * The Trachodon Mummy 1908
 * The Trachodon Mummy, 1917
 * Wyoming Tales and Trails - Lusk
 * Wyoming Tales and Trails - Lusk