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= Edmontosaurus mummy SMF R 4036 =
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Introduction
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The 'Edmontosaurus' mummy SMF R 4036, nicknamed the Senckenberg mummy
or Edmond, is a well-preserved dinosaur fossil in the collection of
the Senckenberg Museum (SMF) in Frankfurt am Main, Germany. It was
found in 1910 in Wyoming, United States, in rocks of the Lance
Formation that date to the late Maastrichtian, close to the
Cretaceous-Paleogene extinction event around 66million years ago. The
mummy is ascribed to the species 'Edmontosaurus annectens' (originally
'Trachodon'), a member of the Hadrosauridae ("duck-billed dinosaurs").
It comprises a nearly complete skeleton that was found wrapped in skin
impressions, a rare case of preservation for which the term 'dinosaur
mummy' has been used. The fingers of the right hand are wrapped in a
mitten-like envelope of skin impressions, initially interpreted as a
paddle unsuited for terrestrial locomotion, thereby reinforcing the
now outdated hypothesis that hadrosaurs were aquatic. The impression
of a horny beak is also preserved with this specimen. Plant remains
found in the body cavity were interpreted as stomach contents,
suggesting a diet of terrestrial plants. It is now believed that this
plant material was washed into the body cavity of the carcass.
It is assumed that the individual died during a drought, in or near a
riverbed. Subsequently, the carcass would have dried out before being
carried away by a sudden flood and been buried rapidly. Sand filled
the body cavity, preserving the three-dimensional shape of the body,
and a biofilm (bacterial mat) on the skin formed a thin crust of clay
that preserved the shape of the skin in positive relief (protruding up
from the surface). The mummy was found by fossil hunter Charles H.
Sternberg and his sons, who sold their numerous finds to museums in
North America and Europe. It is one of the best preserved hadrosaurid
mummies and the second to be discovered, after the first such mummy
was discovered by the Sternbergs in the same region two years earlier.
Discovery and research history
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The mummy was discovered in early September1910 by the Sternbergs, a
family of commercial fossil hunters consisting of Charles H. Sternberg
and his three sons George, Charles, and Levi in rocks of the Lance
Formation in Converse County (today Niobrara County), Wyoming, United
States. The family had worked in this area since 1908, when they
discovered the similar 'Edmontosaurus' mummy AMNH 5060, which was
acquired by the American Museum of Natural History (AMNH) in New York
City. In 1908 and 1909, they had also found two skulls of the horned
dinosaur 'Triceratops', one of which was sold to the Natural History
Museum, London, while the other was bought by the AMNH. In 1910,
preceding the discovery of the mummy, the party had excavated an
'Edmontosaurus' skeleton and four 'Triceratops' skulls, two of which
were acquired by the Senckenberg Museum.
The Senckenberg mummy comes from the southern Schneider Creek (today
spelled 'Snyder Creek'), on the Zerbst Ranch. Charles M. Sternberg,
who had so far been unsuccessful in finding specimens that season,
discovered a (hip) vertebra and a hind limb weathering out of grey
sandstone as he roamed the area in search of fossils with his brother
Levi. The party moved its camp to the site on 4 September and was
joined by the local Lon Galbreath. Their equipment consisted of four
horses, a heavy lumber wagon, and a buggy. The recovery of the fossil
was the most elaborate the family had ever undertaken. Charles H.
Sternberg 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
over , while the entire fossil weighed about . Since the Sternbergs
had no pulley, the block was lifted step by step, by elevating it
using levers of poplar wood and subsequently shoveling sand
underneath. When the block was lifted to a height of , it could be
loaded onto a wagon for transportation to the railway station away in
Edgemont, South Dakota. The excavation and transport took two and a
half months to complete.
Charles H. Sternberg offered to sell the fossil to , paleontologist
and head of the paleontology department of the Senckenberg Museum (,
SMF) in Frankfurt, Germany. Drevermann was able to pay the required
sum of US$2,500 (2500) through a donation from the industrialist
Arthur 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 than Sternberg
was to receive from the Senckenberg Museum. Sternberg wrote in 1917:
The mummy arrived at the Senckenberg museum in 1911. At that time, the
preparators were still occupied with one of the 'Triceratops' skulls
that the museum had received from Sternberg the previous year, so that
the preparation of the mummy began only in 1912. Preparation was
completed in 1920, probably being delayed by World WarI. The mummy was
among the first larger fossils to be prepared using compressed-air
tools, a technique developed from 1914 onwards by Christian Strunz,
the museum's preparator-in-chief. Several German-language publications
on the mummy were published in the early 1920s, focusing on supposed
stomach contents, the anatomy of the skull, and the movements of the
jaws during chewing.
During World War II, a construction of sandbags was built around the
mummy to prevent damage from bombing raids. When the bombings
intensified, the mummy was moved to a safer location outside the city.
On the way back to the museum after the war, however, the mummy fell
off a truck and burst into multiple pieces; the subsequent restoration
took more than 10 years. From 1963-1964, a new cellar was built to
house the mummy, allowing it to be viewed from both the sides and from
the room above. Since the initial 1920s studies, little research had
been done on the specimen until the museum initiated the
"'Edmontosaurus' project" in 2018. This project included the
excavation of about 30 tonnes of a bonebed in the vicinity of the
original excavation site of the mummy. The excavated blocks,
containing hundreds of bones of 'Edmontosaurus' and other animals,
were shipped to Frankfurt and prepared as part of the museum's
exhibition. Further research on the mummy itself was also initiated,
leading to a re-evaluation of the supposed stomach contents and a
paleoenvironmental reconstruction based on pollen from the body
cavity. The mummy, dubbed "Edmond" by the museum, is one of the
museum's most valuable fossils.
Significance and classification
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The Senckenberg specimen was the second dinosaur mummy to be
discovered. The term 'dinosaur mummy' was originally coined by Henry
Fairfield Osborn in 1911 for the 'Edmontosaurus' mummy of the AMNH.
This term was later used to refer to a handful of similar hadrosaurid
("duck-billed dinosaurs") specimens with extensive skin impressions,
all of which have been discovered in North America. A third mummy was
discovered by Barnum Brown in 1912 in Alberta, Canada, and
subsequently described as the new genus 'Corythosaurus'. Yet another
mummy was discovered by Sternberg in 1916, which he sent to London
during World WarI. The transport ship, the , was sunk by a German
raider ship in December 1916, resulting in the loss of this mummy as
well as many other fossils discovered by Sternberg. Additional mummies
have been excavated since the turn of the millennium, such as a
'Brachylophosaurus' mummy nicknamed "Leonardo" and an 'Edmontosaurus'
mummy nicknamed "Dakota".
The mummy belongs to the species 'Edmontosaurus annectens' within
Hadrosauridae, a family of ornithischian () dinosaurs. It was
initially assigned to the genus 'Trachodon', which encompassed nearly
all known hadrosaurid specimens at that time. Osborn initially
assigned the specimen to the species 'Trachodon annectens'. In a 1942
monograph on North American hadrosaurs, Richard Lull and Nelda E.
Wright moved the species together with the mummy into the new genus
'Anatosaurus', as 'Anatosaurus annectens'. In 1990, Michael K.
Brett-Surman and Ralph Chapman proposed that the species actually
belongs within the genus 'Edmontosaurus', which was followed by
subsequent reviews. The majority of dinosaur skin impressions are
referable to hadrosaurids. In North American specimens from the
Maastrichtian age, skin impressions are 31 times more abundant in
association with hadrosaurid specimens than with any other coeval
group. The reasons for this distribution are unclear. Of all known
hadrosaurid skin impressions, 25% belong to 'Edmontosaurus'.
Description
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The skeleton is mostly complete but lacks one of the two hind limbs
and the end of the tail; it is more complete than the AMNH mummy. The
skull is completely preserved, including the impression of the horny
beak and the scleral ring around the pupil of the eye. Sternberg
reported that the trunk and skull together were long, the tail was
long, and the rib cage was wide. The skull is long. The individual
was about 122% the size of the AMNH mummy, and was probably an old
adult.
The bones of the mummy are fully (still in their original anatomical
position) and mostly preserved three-dimensionally, not flattened as
with many other fossils. The forelimbs are oriented backwards and
upwards, and the skull is elevated relative to the trunk. The
preserved hind limb has its fibula (calf bone) and tibia (shin bone)
folded against the femur (thigh bone), while the foot is pointing
downwards. Preserved skin impressions come from the right side of the
trunk and the neck as well as both forearms. Especially well-preserved
skin is found around the right hand. The palm of this hand shows
polygonal scales about in diameter, while those of the upper surface
of the hand are twice this size. Most other skin impressions have been
separated from the skeleton during preparation.
Supposed aquatic lifestyle and posture
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The fingers of both the AMNH and Senckenberg mummies are completely
enclosed in a mitten-like envelope of skin impressions. Osborn, in
1912, interpreted the impressions of the AMNH mummy as interdigital
webbing and the forelimb as a long paddle, indicating an aquatic
lifestyle for hadrosaurids. The idea of an aquatic lifestyle had been
proposed before, but it was only after the discovery of the two
mummies that this idea became the universally accepted doctrine.
According to Lull and Wright, the paddle-like limb of the Senckenberg
mummy confirmed that these animals were aquatic, and the lack of foot
pads or hooves showed that the forelimbs were unsuited for walking. In
his 1911 account on the discovery of the Senckenberg mummy, Charles
Hazelius Sternberg speculated that trachodons "[...] lived in the
water, and only came on the land at the peril of their lives, as they
had no means of defense against the king of carnivorous reptiles,
'Tyrannosaurus' [...]".
In 1964, John H. Ostrom argued that hadrosaurids must have fed on
resistant terrestrial plants rather than on soft aquatic ones, and
that the skeleton was adapted for a bipedal locomotion on land. The
hypothesis of an aquatic lifestyle was finally abandoned after Robert
Bakker, in 1986, argued that the skin between the fingers of the AMNH
mummy was actually the remnant of a fleshy pad enveloping the hand
that had dried out and flattened during mummification. Furthermore,
Bakker argued that the fingers were short and could hardly have been
spread apart, which distinguishes them fundamentally from the long,
spread toes of today's paddling animals such as ducks.
In his 1911 account on the discovery of the mummy, Charles Hazelius
Sternberg noted that the sprawling posture of the preserved hind limb
is comparable to that of the AMNH mummy, and suggested that this could
have reflected the original posture of the living animal--in
contradiction with skeletal mounts of the time, which often showed
more erect limbs. Sternberg noted: "He walked like a lizard, with body
close to the ground and tail dragging out behind." In 1968, Bakker
showed that dinosaurs had erect limbs, and in 1970, Peter Galton
showed that hadrosaurids had horizontal trunks and tails that were
held clear off the ground.
Supposed stomach contents
===========================
Following the preparation of the mummy in Frankfurt, the paleobotanist
Richard Kräusel studied an earthy mass of plant remains found on the
in the hip region, which he considered probable stomach contents based
on their composition and location. This mass mostly comprised conifer
needles ('Cunninghamites elegans' according to Kräusel) and parts of
tree branches, as well as seeds or fruits. These remains suggested a
diet consisting of terrestrial plants, conflicting with the prevalent
belief at that time that hadrosaurs were aquatic animals. Kräusel
therefore suggested that the animal must have left the water for
feeding. He presented his findings in 1921 at the annual meeting of
the , the German paleontological society, in Frankfurt. In the
discussions following the talk, Othenio Abel argued that these remains
could have simply been washed into the cadaver, a possibility that was
considered unlikely by Kräusel, since pollen, fungi, or eggs of water
insects, which he would have expected in a washed-in mass, are
lacking. Carl Wiman argued that stomach contents do not necessarily
reflect an animal's diet, since food items could have been swallowed
accidentally, as indicated by plant remains found in specimens of the
modern platypus. Drevermann, defending Kräusel's hypothesis, argued
that the remains had been found on the pubis bone of the mummy, where
they could have fallen when the carcass was lying on its right side.
During the following century, the supposed stomach contents were often
regarded as one of the best available pieces of evidence for the diet
of 'Edmontosaurus' and hadrosaurids in general, although the
credibility of this evidence was repeatedly questioned. Although
Sternberg had reported stomach contents from the AMNH mummy, these
have never been studied. Ostrom, in his 1964 paper, cited the stomach
contents of the Senckenberg mummy as further evidence for a diet
consisting of terrestrial plants, questioning the aquatic lifestyle
hypothesis which was universally accepted at the time. Later,
different authors noted that since the mass was removed from the mummy
and macerated it was no longer available for research, and that
Kräusel's hypothesis can no longer be validated.
, in 2020, analyzed the available historic accounts, microscope slides
of plant remains prepared by Kräusel, and additional plant remains
found within the sandstone that surrounded the mummy. Uhl concluded
that Kräusel's plant remains were probably not stomach or gut
contents: The plant fragments are much smaller than those of other
known hadrosaurid gut contents and coprolites, and are more comparable
to the plant remains extracted from the surrounding rock that were
transported by water. Furthermore, the mass described by Kräusel was
found atop the of the hip and therefore in the upper region of the
body cavity, which is an unlikely location for stomach or gut contents
as the animal was found lying on its underside. Uhl hypothesized that
the mass of plant remains could have formed after most of the body
cavity had already been filled with sand by the action of a river,
leaving a chamber that acted as a sediment trap where the fine plant
detritus that was suspended in the water could accumulate.
Beak and chewing
==================
The tip of the snout is strongly widened in top view, reaching a width
of . The upper jaw preserves an impression of the horny beak, which is
vertical and, in front view, rectangular, with a wavy surface. It
protrudes past the lower margin of the upper jaw by . The lower beak
is not preserved but would have been much smaller, fitting within the
upper beak to allow for cropping of vegetation. A similar beak
impression had been briefly described in 1883 by Edward Cope in his
'Diclonius mirabilis' (now 'Edmontosaurus annectens'). Jan Versluys,
in a 1923 publication on the Senckenberg mummy's skull, noted that
Cope had assigned the beak to the lower jaw, but that the mummy shows
that it actually belonged to the upper. Some early figures published
by Cope in the 1880s showed the snout of 'Trachodon' to be flat in
side view, similar to the bills of birds such as spoonbills and
shovelers. Abel, in 1912, might have been misled by Cope's figures
when suggesting that 'Trachodon' would have fed under water in the
same fashion as these birds. Versluys argued that Cope's fossils were
flattened during fossilization, as the undeformed skull of the mummy
demonstrates that the bill was actually quite deep, unlike those of
ducks or spoonbills. Versluys suggested that the horny beak might have
been used to crop twigs or bark from tree trunks, or plants from stony
or sandy ground. Based on the pronounced hyoid bone (tongue bone) of
the mummy, Versluys also suggested that 'Trachodon' had a
well-developed tongue that was possibly prehensile as in giraffes and
could have been used to grasp vegetation.
Versluys also attempted to reconstruct the movements of the jaws
during chewing. The grinding surfaces of the tooth row are inclined by
around 50° and the jaw joint is asymmetric, with a deeper outer part
and a shallower inner part. Furthermore, the contact surface of the
left and right halves of the lower jaw is smooth, suggesting a
flexible symphysis that allowed for movements between the two halves
of the lower jaw. Versluys concluded that these features can only be
explained by a complex chewing motion that involved a rotation of the
lower jaws along their long axes. It is now known that ornithopods
indeed developed a sophisticated chewing mechanism with an efficiency
that is otherwise only reached by mammals. This mechanism also
involves movements of other parts of the skull (pleurokinesis).
Taphonomy
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Several authors discussed the question of how the animal died and what
circumstances led to its exceptionally good preservation. 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 and position of the Senckenberg mummy differed: the skin
did not adhere closely to the bone, but rather traced the original
body contour. In addition, the mummy was not lying on its back like
the AMNH mummy, but on its underside, with one hind limb extended
downwards and the other drawn against the body. The forelimbs were
stretched upwards, with the palms facing upwards. The mummy was found
in an inclined position, with the upward-pointing snout higher than
the preserved hind foot, measured perpendicular to the rock layers.
The Sternbergs suggested that the animal sank into soft sediment,
possibly quicksand, and 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 quicksand hypothesis
cannot be confirmed by sediment samples of the site of discovery, but
agreed that the carcass must have been buried rapidly.
In 2020, Uhl stated that the mummy was surrounded by brownish fine- to
medium-grained sandstone, but that sedimentological structures that
might indicate the mode of preservation are not visible in surviving
rock samples and were not recorded by the Sternbergs. It is likely
that the sandstone surrounding the mummy was fluvial (laid down by
rivers) and that the mummy was not transported over a long distance
before burial, given the well-preserved skin impressions. The body
cavity of the mummy contained fossils such as plant remains, leaf
impressions, and a fish, which may have been washed into the carcass
after the death of the animal.
In 2025, Paul Sereno and colleagues proposed that the Senckenberg
mummy and other hadrosaur mummies of the Lance Formation derive from
individuals that died in or near a riverbed during a period of
drought. None of the mummies show signs of scavenging, possibly
because there were so many carcasses available that many remained
untouched. After a short transportation by a sudden flood, the mummies
would have been rapidly buried. Sereno and colleagues suggested that
the entire mummification process from death to burial happened within
a single season, probably in a matter of weeks. Once buried, sediment
would have quickly entered through holes in the cadaver, filling the
body cavity and therefore preserving the three-dimensional shape of
the body. A biofilm (layer of microorganisms) would then have formed
on the outer surface of the body and attracted clay minerals from the
surrounding sediment due to electrostatics, forming a clay layer that
is less than in thickness. This clay layer retained the shape of the
skin in positive relief after the decay of the latter. Therefore,
Sereno and colleagues argued that the skin is not preserved as
impressions, despite being commonly referred to as such. Instead,
fossils like these should be termed "skin renderings", and, more
specifically, "templates" or "masks".
Locality and paleoenvironment
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The Senckenberg mummy is one of six dinosaur mummies found in a small
area measuring in diameter. This area, dubbed the "mummy zone" by
Sereno and colleagues in their 2025 study, yielded three other
'Edmontosaurus' mummies, the AMNH mummy as well as "Ed Jr." and "Ed
Sr.". The zone also yielded mummified specimens of 'Triceratops'
("Lane") and 'Tyrannosaurus' ("Rex Jr."). Sereno and colleagues
determined that the coordinates of the Senckenberg mummy's discovery
site are approximately . Therefore, the Senckenberg mummy is the
northernmost mummy of the zone, having been discovered northeast of
the AMNH mummy. Vertically, the "mummy zone" encompasses of the upper
part of the Lance Formation. The Senckenberg mummy was probably
discovered at an altitude of , and is therefore the lowest (and
oldest) mummy of the zone. Sereno and colleagues argued that the
"mummy zone" was an area of rapid subsidence (downward movement of the
Earth's surface) that resulted in high sedimentation rates, and was
subjected to pronounced cycles of droughts and subsequent floods. The
combination of these factors would have resulted in the exceptional
abundance of mummies. These authors also argued that 'Edmontosaurus'
mummies are comparatively common because this genus preferred habitats
closer to the coast where sedimentation rates were higher, while
'Triceratops' tends to occur further inland.
In a 2021 study, Haytham El Atfy and Uhl analyzed microscopic plant
material extracted from rock samples recovered from the body cavity of
the mummy. To isolate this material, the rock samples were dissolved
using acids; two out of seven samples yielded useful contents. The
most common component of the extracted material was charcoal,
suggesting that wildfires would have been frequent in the Lance
Formation habitat. Spores, especially those of mosses and ferns such
as 'Azolla', were more common than angiosperm and gymnosperm pollen.
Angiosperm pollen confirm a late Maastrichtian age, close to the
Cretaceous-Paleogene extinction event around 66.043million years ago.
The recorded plant species suggest a forested habitat, with an
understory dominated by ferns, mosses, and angiosperms, and an upper
story comprising conifers (Pinaceae and Cupressaceae) and cycads. The
climate was probably warm and humid.
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