Trachodon mummy

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The Trachodon mummy, illustration from the description from 1912

The Trachodon mummy is a naturally formed mummy of a dinosaur . It was discovered in Wyoming ( USA ) in 1908 and is attributed to the dinosaur species Edmontosaurus annectens (originally Trachodon annectens ), a member of the Hadrosauridae ("duck-billed dinosaur"). The Trachodon mummy is the first of seldom found dinosaur fossils to show extensive skin impressions enveloping the body, which led to the name “dinosaur mummy”. The unusually good preservation of this detailed fossil has significantly shaped the scientific ideas about the biology of the Hadrosaurids. Imprints of the skin found between the fingers of the mummy were interpreted as webbed feet, which was used as a decisive argument for an aquatic way of life for the Hadrosaurids. Today this theory is considered refuted.

The mummy was discovered and recovered by the Sternberg family ( Charles H. Sternberg and Sons), who are famous for their numerous finds, particularly of dinosaur fossils. Today the mummy is on display in the American Museum of Natural History (AMNH) in New York , the copy number is AMNH 5060 . In 1910 the Sternberg family discovered a second Edmontosaurus mummy in the same area, which they sold to the Senckenberg Nature Museum in Frankfurt am Main ( Senckenberg mummy ), where it is still on display today.

discovery

Badlands the Lance Formation along the Cow Creek
The Trachodon mummy on display at the American Museum of Natural History (2008)

The Trachodon mummy was discovered and recovered in 1908 by Charles Hazelius Sternberg and his three sons George , Charles and Levi . Sternberg was an independent fossil hunter who offered his finds for sale to various museums in North America and Europe. His sons initially worked as their father's assistants, but later rose to become recognized paleontologists themselves . In 1908 Sternberg wanted to venture into a new work area, the Lance Creek area in eastern Wyoming. In advance he tried to find buyers for the expected fossil finds, and wrote to the British Museum of Natural History that he knew where in Wyoming a fossil of the horned dinosaur Triceratops could be found. The museum agreed that it would buy up good fossil finds should any be made. The Sternberg expedition set out from their family home in Kansas early in the spring and reached the Lance Creek area in July. The plan was to explore an approximately 1,000 square miles (2590 km²) uninhabited area north of the North Platte River and south of the Cheyenne River in Converse County (now Niobrara County ). The badlands prevailing here open up rocks of the late Upper Cretaceous ( Maastrichtian ), which are known today as the Lance Formation . The area was previously explored intensively by paleontological expeditions; before beginning his search, Sternberg learned that the American Museum of Natural History had been unsuccessful in the field for years.

The first few weeks of the search were unsuccessful. Sternberg wrote: “ Day after day hoping against hope we struggled bravely on. Every night the boys gave answer to my anxious inquiry, What have you found? Nothing. ”(German:“ Day after day, hoping against all hope, we eagerly struggled on. Every evening the boys answered my anxious inquiry, What did you find? Nothing. ”) At the end of August, Sternberg finally came across one from the Horn scented out of rock; the subsequent excavation brought to light a 198 centimeter long Triceratops skull. Shortly afterwards, the eldest son George discovered bones chewing out of the rock when he and the youngest son Levi were walking across unexplored territory. Levi found other bones in the immediate vicinity that apparently belonged to the same skeleton. By this point, the group was within 65 miles (105 km) of their base camp and food supplies were running low. Sternberg instructed George and Levi to carefully remove the sandstone above the skeleton, and set off for Lusk with Charles to buy new supplies and send the skull to the British Museum. On the third day after their father's departure, George and Levi had already recognized that they were looking at an apparently complete copy lying on its back. When George removed a large piece of sandstone from the chest region of the skeleton, he discovered, to his surprise, a perfectly preserved skin impression. In 1930 George wrote: “ Imagine the feeling that crept over me when I realized that here for the first time a skeleton of a dinosaur had been discovered wrapped in its skin. That was a sleepless night for me. "(German:" Imagine the feeling that overcame me when I realized that this was the first time a dinosaur skeleton and its skin had been discovered. That was a sleepless night for me. ") When Sternberg finally returned on the fifth day , George and Levi were out of food; for the last two days they had to live on unsalted potatoes. Nonetheless, they had completely removed the sandstone on top; the excavation was 3.6 meters wide, 4.5 meters long and 3 meters deep.

When Henry Fairfield Osborn , director of the American Museum of Natural History, heard of the find, he immediately sent a staff member to Wyoming to purchase the fossil for the museum. Osborn knew about the arrangement between Sternberg and the British Museum, but appealed to Sternberg's patriotism and promised a permanent display of the fossil. Eventually the museum bought the mummy for $ 2,000. In the American Museum, the uncovering of the skin impressions by the taxidermist Otto Falkenbach was completed, then the fossil was scientifically processed by Osborn and Barnum Brown and finally exhibited in the museum. In the exhibition, the specimen, which is enclosed in a protective glass cover, is shown in its original location; no restorations of missing parts have been made.

Significance and systematic classification

The Trachodon mummy in side view
Skin prints of the Trachodon mummy. The right figure corresponds to the one marked A, the left one to the hatched area marked B in the outline drawing of the mummy shown below .

The scientific value of the mummy lies in its unusually good degree of preservation, the connection between the bones in their original anatomical structure and the extensive remains of skin. Osborn wrote in 1911: “ This truly wonderful specimen, therefore, nearly doubles our previous insight into the habits and life of a very remarkable group of reptiles. ”(German:“ This really wonderful specimen gives us almost a doubling of our previous insights into the habits of a very remarkable group of reptiles ”) Since skin prints of hadrosaurids were previously known only from a few fragments, the trachodon mummy wrapped in skin prints became a paleontological sensation . However, Osborn wrote in 1912 that the famous type specimen of Trachodon mirabilis (AMNH 5730), which was found by Jacob Wortman in 1884, was originally also surrounded by a shell of skin impressions. Most of these prints were destroyed when the skeleton was recovered, which is why there are only three fragments from the tail region. As Osborn further noted, it is very difficult to uncover the very thin layer of skin imprints in an excavation; for example, many finds of fossil skin may have been lost in previous years because they were neither expected nor recognized.

The Trachodon mummy is assigned to the Hadrosauridae ("duck-billed dinosaurs"), a group within the Ornithischia ("bird pelvic dinosaurs"). Barnum Brown initially identified the mummy as Trachodon annectens . The genus Trachodon were virtually assigned all known Hadrosauriden-finds at this time. From 1942 the mummy was carried under the new species Anatosaurus copei , which in 1990 was transferred to an independent genus, Anatotitan . Today, most researchers consider Anatotitan copei to be identical to Edmontosaurus annectens . A large part of all known dinosaur skin prints are ascribed to the Hadrosauridae; In the Maastrichtian region of North America, hadrosaurid fossils are found 31 times more often with skin prints than fossils from other groups. The reasons for this distribution are unclear. The genus Edmontosaurus accounts for 25% of all known skin prints of hadrosaurids.

Description and interpretations

Outline drawing of the mummy (ventral view)

Most of the mummy has been preserved and the bones are still in their original anatomical bond. The hind feet, the rear section of the pelvis and the tail are missing; these parts were lost to erosion even before the fossil was discovered. Fossils are very often flattened during fossilization; however, the Trachodon mummy has been preserved in three dimensions. The specimen lies on its back with the head and neck turned down and toward the right side of the body. The knees are drawn up while the front legs are straight up. The chest is open. Almost two thirds of the entire skin surface are in partly excellent condition, which led Osborn to call it the “dinosaur mummy”. The skin prints are pressed tightly against the bones and pulled into the body between the bones. Presumably, when it was discovered, the entire skeleton was surrounded by skin impressions, which, however, were partially destroyed when the fossil was removed from the rock. The skin prints can be found on the front legs, neck and throat, the chest region and on the right side of the trunk. Sternberg also pointed to the preservation of muscle prints. Carpenter (2007) stated that prints from internal organs may also be present; To check this possibility, however, detailed computed tomography and X-ray analyzes are necessary.

skin

Drawing of a section of the skin in the abdominal region

The skin appears very thin and delicate in relation to body size. As is typical for dinosaurs, the scales consist of non-overlapping scales ( tubercles ). The base area is formed by rounded “basal tubercles” with a diameter of 1 to 3 millimeters, which are interrupted by island-like clusters of larger, usually less than five millimeters large, polygonal “plaster tubercles”. The clusters can consist of 20 to several hundred plaster tubercles. They are bordered by intermediate tubercles, which mediate in size and shape between the basal tubercle and the plaster tubercle. In the chest and stomach area, the clusters are small, oval shaped and arranged in irregular longitudinal rows. They grow larger on the sides (5 to 10 centimeters), their shape is more irregular. The largest clusters are found above the basin and measure 50 centimeters in diameter; similarly large clusters were presumably present over the entire back.

Muscles and joints were generally covered with smaller tubercles to allow greater flexibility - larger tubercles are found in the areas that are tightly pressed against the bones. The largest preserved scales are found on the outside of the arms; these polygonal tubercles reach a diameter of one centimeter. The inside of the arms, on the other hand, was completely covered by small tubercles. The thigh also shows relatively small tubercles on the inside; from the outside no impressions have survived. Skin impressions from the skull can only be found within the large skull window that houses the nostrils. Here the skin is smooth and wrinkled; Tubercles are completely absent. A deepening of the skin in the anterior section of the skull window could mark the location of the fleshy nostrils.

Skin comb

The Trachodon mummy is attributed to the species Edmontosaurus annectens (picture). The artistic reconstruction of life shows the skin ridge segmented into flaps.

A skin impression 25 centimeters long and 7 to 8 centimeters deep has been preserved above the cervical spine . Osborn interpreted this area as part of an ornamental ridge of skin that extended along the center line of the neck and back. Above the vertebral joints, the comb is folded into folds to ensure the mobility of the neck, which makes the comb appear like a frill. There is a large, oval cluster of plaster tubercles between each of the folded areas of the ridge. Osborn noticed that the top of the ridge was destroyed when the mummy was recovered, which is why the height of the ridge can no longer be determined. Presumably the ridge was extended upwards by at least one more row of clusters. Stephen Czerkas (1997) argued that the crest was not folded in the live animal; the folding was a result of mummification and caused by dried-up neck bands . An Edmontosaurus fossil described by John Horner in 1984 shows that the upper edge of the skin ridge was segmented into regular, rectangular lobes, at least in the tail area.

hand

Drawing of the bottom of the right hand. The metacarpal bones and fingers enclosed by the skin can be seen.

The Trachodon mummy enabled the first accurate reconstruction of the hand skeleton of a Hadrosaurid. Barnum Brown (1912) showed that the wrist did not consist of two complete rows of ossified carpal bones , as Othniel Charles Marsh had assumed in his widespread reconstruction of 1892, but that only two ossified carpal bones were present. In the mummy, these elements lie directly one above the other and above the third metacarpal bone . This is likely to be the original live position as the bones in both hands are preserved in the same position. Brown further pointed out that the first finger was missing and fingers 2, 3, 4 and 5 each consisted of three phalanges. Marsh had reconstructed the first finger as a reduced element with only two phalanges; the fifth finger was not present in his reconstruction.

The fingers of the Trachodon mummy are partially connected to one another by a covering of skin prints. Osborn argued in 1912 that it was in this skin envelope around webbed acted and acts the forelimb as paddles, which is a clear indication of an aquatic lifestyle of Trachodon was and probably other representatives of Trachodontidae (= Hadrosauridae). The webbed fingers not only connected the fingers, but also extended up to five centimeters above the fingertips. Also noteworthy are the lack of clearly pronounced hooves and large, fleshy foot pads on the forelegs - features that are to be expected in a primarily rural animal. With the Senckenberg mummy , another trachodon specimen with web-like structures was discovered in 1910 . While the hypothesis of an aquatic way of life was previously considered controversial and speculative, it became the undisputed doctrine with the discovery of these two mummies. Charles H. Sternberg wrote in 1917: “ I was reluctently giving up Marsh's and Cope's ideas; they believed these dinosaurs lived on land, feeding off the tender foliage of trees […] Entirely different views are held now […] These [the duck-bills] lived in the water instead on land, and consequently they had thin skin and strong paddles, or rather webbed feet. ”(German:“ I was reluctant to give up Marsh and Cope's ideas; they believed that these dinosaurs lived in the country and fed on the soft leaves of trees […] Today, completely different opinions are represented […] The duckbill dinosaurs lived in water instead of on land, and consequently had thin skin and strong paddles, or rather webbed feet. ")

It was only in 1964 that John H. Ostrom reported doubts: This researcher was able to show that hadrosaurids did not feed on soft aquatic plants as previously assumed, but that their elaborate chewing apparatus was designed to crush resistant plant material such as conifers . The skeletal anatomy would suggest highly specialized, two-legged locomotion on land. Ostrom noted that hadrosaurids did not show skin bone plates or similar structures to defend against predators, as found in many other herbivorous dinosaurs. Thus, the webbed feet possibly served to enable an escape into the water in case of danger. Robert Bakker (1986) finally argued that the animal had no webbed feet and that the remains of skin stretched between the fingers represent the remains of a fleshy hand pad that was dried out and flattened in the course of mummification. Very similar skin structures from foot pads can be found on today's mummified camel carcasses. In addition, the fingers are short and can hardly be spread apart, which fundamentally distinguishes them from the long, splayed toes of today's paddling animals such as ducks. Bakker sums up: “ Far from being the best, the duckbills must have been the clumsiest and slowest swimmers in all the Dinosauria. ”(German:“ The duck-billed dinosaurs were by no means the best, but the clumsiest and slowest swimmers within the entire Dinosauria. ”) Today the webbed hypothesis is considered to be refuted.

Ossified tendons and stomach contents

The Senckenberg mummy ( Senckenberg Naturmuseum , Frankfurt am Main)

In 1909 Charles H. Sternberg discovered that hundreds of pencil-thick ossified tendons had been preserved along the spinal column . Sternberg speculated that these tendons were used for defense and could not be penetrated by the claws of predatory dinosaurs such as the contemporary tyrannosaurus . Today it is known that these tendons stiffened the spine , probably to counteract the bending forces on the spine when walking, and that a large part of the tail not preserved in the Trachodon mummy was stiffened by such tendons.

Sternberg also reported charred food residues that were discovered in the stomach region of the Trachodon mummy. An analysis of these remains has not yet been carried out. Kräusel (1922) investigated a concretion of brown plant material in the Senckenberg mummy, which mainly consisted of needles and branches from conifers. With both mummies, however, it cannot be ruled out that the plant material was only washed into the abdominal cavity after the death of the animal.

Color sample

Osborn observed in 1912 that the plaster tubercle clusters on the top of the trunk and limbs were significantly more numerous than on the bottom. Consequently, they would dominate in areas exposed to the sun; In many of the reptiles living today, these sun-exposed areas are covered with most of the pigments . From these observations, Osborn hypothesized a connection between pigmentation and scaling: the plaster tubercle clusters could have represented darker-colored areas on a light-colored surface. The irregular distribution of the clusters would indicate an irregular color pattern. The most elaborate color pattern can be found on the skin ridge of the neck. However, Osborn admitted that in today's lizards the distribution of pigments is completely independent of the type of scaling. Today's researchers found that statements about the color pattern are not possible.

Taphonomy

Various authors dealt with the question of how the animal was killed and what circumstances led to the exceptionally good preservation. Charles H. Sternberg (1909) and Charles M. Sternberg (1970) assumed death in the water. The gases that collected in the abdominal region after death would have floated the carcass, with the abdomen pointing upwards and the head resting under the shoulder. Arrived at the embedding site, the carcass was lying on its back and was covered in sediment . The skin was drawn into the body cavity by the load of the sediments or by the escape of the gases. In 1911, Osborn proposed a different scenario: The animal died a natural death and the carcass would have been exposed to the sun for a long time in a dry river bed, unaffected by scavengers . Muscles and intestines were completely dried out and thus shriveled, causing the hard and leathery skin to sink in and finally to adhere tightly to the bones. The resulting natural mummy was hit by a sudden flood at the end of the dry season, transported a distance and very quickly covered by sediments at the embedding site. The fine grain size of the sediment (fine river sand with sufficient clay content ) would have resulted in the perfect imprint of the filigree skin structures, even before the hardened skin could soften. Today, Osborn's hypothesis is considered the most likely.

Aerial view of a meandering river. You can see the sliding slopes (sand point bar) on the inside and the impact slopes (cutbank) on the outside of the river loops.

One can only speculate about the cause of death of the animal. Kenneth Carpenter (2007) considered starvation during a drought to be the most likely cause of death. The mummy, with its skin sunk around its bones, resembles the cadavers of today's animals as they are found during droughts. In addition, the carcass was not affected by scavengers . Such a circumstance can be observed during today's droughts, when drought keeps scavengers away from the affected area, or such a large number of carcasses accumulates that it can no longer be dealt with by the existing scavengers. Finally, Carpenter notes that today's great artifacts are tightly bound to water during droughts to prevent overheating. The main cause of death for these animals during droughts is starvation, not dying of thirst. The Trachodon mummy was discovered in river sediments; the animal must therefore have died near a river or at least a dry river bed.

The sediments from the site were deposited by a meandering river. Such a river constantly changes its course by removing the bank on the outside of the river loops ( impact slope ) and depositing sediment on the inside ( sliding slope ) . The sliding slope forms a characteristic sediment sequence, the sliding slope sequence . Carpenter deduces from a photo taken during the excavation that the fossil was discovered within a sliding slope sequence, i.e. the carcass was embedded on a sliding slope. Carpenter suggested that the carcass was embedded during flood events after a drought ended. According to Carpenter, an important factor for rapid embedding is the fact that the carcass acts as an obstacle in the flow: When the carcass circulates, the flow speed of the water increases, which removes sediment. The carcass would gradually sink into the hollow created in this way. The sediment required for further embedding had entered the river upstream through collapsing slopes, which the high clay content of the sandstones would indicate. The sediment load of the river would have been deposited, especially at the end of the tide, if the flow velocity and thus the transport capacity of the river decreased. Thus, the carcass was embedded within hours or at most a few days.

What happened after it was embedded is difficult to reconstruct, especially because there are no more samples of the sandstone that immediately surrounded the mummy today. The slow bacterial decomposition of the now moist carcass probably started first. Carpenter emphasizes that the excellent preservation of the fossil was only made possible by minerals formed by bacteria ( biomineralization ). These minerals would have solidified the clay-rich sand surrounding the mummy, which made the unusual three-dimensional preservation possible. At the same time, the surface structure of the skin was preserved as an imprint on the original contact area between sand and carcass . In addition, the mineralization anchored the bones in their anatomical position and thus prevented them from falling apart as the soft tissue decayed. Important minerals formed at the time are the calcium carbonate calcite and the iron carbonate siderite , which - oxidized to limonite - is responsible for the rusty color of the mummy. After the more or less complete decomposition of the soft tissue, a cavity remained in the cemented sediment, which was subsequently filled with sand. The skin prints on the inner wall of the cavity were also filled in. In the course of normal rock formation , this sand was also cemented. Thus, the soft body tradition of the Trachodon mummy is to a certain extent comparable with the formation of stone cores in invertebrate marine animals with exoskeleton.

literature

  • Kenneth Carpenter: How to Make a Fossil: Part 2 - Dinosaur Mummies and Other Soft Tissue . In: The Journal of Paleontological Science . 2007, p. 5-14 .
  • Phillip Lars Manning: Grave secrets of dinosaurs: soft tissues and hard science . National Geographic, Washington, DC 2008, Chapter four: Dinosaur Mummies.
  • Henry Fairfield Osborn: Integument of the iguanodont dinosaur Trachodon . In: Memoirs of the American Museum of Natural History . tape 1 , 1912, p. 30-54 .
  • Henry Fairfield Osborn: A Dinosaur Mummy . In: The American Museum Journal . tape 11 . New York 1911, p. 7-11 .
  • Katherine Rogers: The Sternberg Fossil Hunters: A Dinosaur Dynasty . Mountain Press Publishing Company, 1999, ISBN 0-87842-404-0 , pp. 106-121 .
  • Charles H. Sternberg: The Life of a Fossil Hunter . Henry Holt and Company, New York 1909, p. 270-277 .

Individual evidence

  1. ↑ a b c d e Phillip Lars Manning: Grave secrets of dinosaurs: soft tissues and hard science . National Geographic, Washington, DC 2008, Chapter four: Dinosaur Mummies.
  2. ^ A b c Mark A. Norell, Eugène S. Gaffney, Lowell Dingus: Discovering Dinosaurs: Evolution, Extinction, and the Lessons of Pre-History . University of California Press, 2000, ISBN 0-520-22501-5 , Edmontosaurus annectens, pp. 154-155 .
  3. ^ A b c Edwin Harris Colbert: The Great Dinosaur Hunters and Their Discoveries . Courier Dover Publications, 1984, ISBN 0-486-24701-5 , pp. 184, 195-197 .
  4. ↑ a b c d e f g Katherine Rogers: The Sternberg Fossil Hunters: A Dinosaur Dynasty . Mountain Press Publishing Company, 1999, ISBN 0-87842-404-0 , pp. 107-108, 110-115 .
  5. ↑ a b c d e f g h i j Charles H. Sternberg: The Life of a Fossil Hunter . Henry Holt and Company, New York 1909, p. 270-277 .
  6. ^ A b c d Charles H. Sternberg: Expedition to the Laramie Beds of Converse County, Wyoming . In: Transactions of the Kansas Academy of Science . tape 22 , December 31, 1909, pp. 113-116 .
  7. ↑ a b c d e f g h i j k Henry Fairfield Osborn: Integument of the iguanodont dinosaur Trachodon . In: Memoirs of the American Museum of Natural History . tape 1 , 1912, p. 33-35, 46-54 .
  8. ^ A b c Henry Fairfield Osborn: A Dinosaur Mummy . In: The American Museum Journal . tape 11 . New York 1911, p. 7-11 .
  9. ^ Benjamin S. Creisler: Deciphering duckbills: a history in nomenclature . In: Kenneth Carpenter (Ed.): Horns and Beaks. Ceratopsian and Ornithopod Dinosaurs . Indiana University Press, Bloomington 2007, pp. 196, 198 .
  10. ^ A b Richard Swann Lull, Nelda E. Wright: Hadrosaurian Dinosaurs of North America . In: Geological Society of America Special Papers . No. 40 , 1942, pp. 113 .
  11. ↑ Ralph E. Chapman, Michael K. Brett-Surman: Morphometric observations on hadrosaurid ornithopods . In: Kenneth Carpenter, Philip J. Currie (Eds.): Dinosaur Systematics: Perspectives and Approaches . Cambridge University Press, Cambridge 1990, ISBN 0-521-43810-1 , pp. 177 .
  12. ^ John R. Horner, David B. Weishampel, Catherine A. Forster: Hadrosauridae . In: David B. Weishampel, Halszka Osmólska, Peter Dodson (eds.): The Dinosauria . 2nd Edition. University of California Press, Berkeley 2004, ISBN 0-520-24209-2 , pp. 460 .
  13. ↑ a b Matt Davis: Census of dinosaur skin reveals lithology may not be the most important factor in increased preservation of hadrosaurid skin . In: Acta Paleontologica Polonica . tape 59 , no. 3 , 2014, p. 601–605 , doi : 10.4202 / app.2012.0077 .
  14. ↑ a b c d e f Kenneth Carpenter: How to Make a Fossil: Part 2 - Dinosaur Mummies and Other Soft Tissue . In: The Journal of Paleontological Science . 2007, p. 5-14 .
  15. ↑ Stephen A. Czerkas: Skin . In: Philip J. Currie, Kevin Padian (Eds.): Encyclopedia of Dinosaurs . Academic Press, San Diego, 1997, pp. 671-672 .
  16. ^ John R. Horner: A "Segmented" Epidermal Tail Frill in a Species of Hadrosaurian Dinosaur . In: Journal of Paleontology . tape 58 , no. 1 , January 1984, pp. 270-271 .
  17. ↑ Michael K. Brett-Surman, Jonathan R. Wagner: Discussion of Character Analysis of the Appendicular Anatomy in Campanian and Maastrichtian North American Hadrosaurids - Variation and Ontogeny . In: Kenneth Carpenter (Ed.): Horns and Beaks: Ceratopsian and Ornithopod Dinosaurs . Indiana University Press, Bloomington, Indiana 2007, ISBN 0-253-34817-X , pp. 143-144 .
  18. ^ A b Barnum Brown: The osteology of the manus in the family Trachodontidae . In: Bulletin of the American Museum of Natural History . tape 31 , 1912, pp. 105-108 .
  19. ↑ a b c Catherine A. Forster: Hadrosauridae . In: Philip J. Currie, Kevin Padian (Eds.): Encyclopedia of Dinosaurs . Academic Press, San Diego, 1997, pp. 294, 297 .
  20. ↑ a b c Robert T. Bakker: The dinosaur heresies . William Morrow and Company, Inc., New York 1986, ISBN 0-688-04287-2 , pp. 146-159 .
  21. ^ A b John H. Ostrom: A reconsideration of the paleoecology of hadrosaurian dinosaurs . In: American Journal of Science . tape 262 , October 1964, p. 975-977, 995-996 .
  22. ^ Charles H. Sternberg: Hunting dinosaurs in the bad lands of the Red Deer River, Alberta, Canada: a sequel to The life of a fossil hunter . The world company press, Lawrence, Kansas 1917, p. 7-8 .
  23. ^ Charles H. Sternberg: A New Trachodon from the Laramie Beds of Converse County, Wyo. In: Science . tape 29 , no. 749 , 1909, pp. 753-754 .
  24. ^ A b Philip J. Currie, Eva B. Koppelhus, A. Fazal Muhammad: "Stomach" contents of a Hadrosaur from the Dinosaur Park Formation (Campanian, Upper Cretaceous) of Alberta, Canada . In: Ailing Sun, Yuanqing Wang (Ed.): Sixth Symposium on Mesozoic Terrestrial Ecosystems and Biota, Short Papers . China Ocean Press, Beijing 1995, p. 111-114 .
  25. ^ A b Charles M. Sternberg: Comments on Dinosaurian Preservation in the Cretaceous of Alberta and Wyoming . In: Publications in Palaeontology . No. 4 . Ottawa 1970, pp. 3-4 .
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