Part 5 (1/2)
Trachodon was not provided with horns, spines or plated armor, but it was sufficiently protected from carnivorous land forms by being able to enter and remain in the water. Its skin was covered with small raised scales, pentagonal in form on the body and tail, where they were largest, with smaller reticulations over the joints but never overlapping as in snakes or fishes. A Trachodon skeleton was recently found with an impression of the skin surrounding the vertebrae which is so well preserved that it gives even the contour of the tail as is shown in the ill.u.s.tration (fig. 32).
”During the existence of the Trachodonts the climate of the northern part of North America was much warmer than it is at present, the plant remains indicating a climate for Wyoming and Montana similar to what now prevails in Southern California. Palm leaves resembling the palmetto of Florida are frequently found in the same rocks with these skeletons. Here occur also such, at present, widely separated trees as the gingko now native of China, and the Sequoia now native of the Pacific Coast. Fruits and leaves of the fig tree are also common, but most abundant among the plant remains are the Equisetae or horsetail rushes, some species of which possibly supplied the Trachodons with food.
[Ill.u.s.tration: Fig. 29.--Restoration of the Duck-billed Dinosaur Trachodon. This restoration, made by Mr. Knight under supervision of Professor Osborn, embodies the latest evidence as to the structure and characteristic poses of these animals, the character of the skin and their probable habits and environment. _After Osborn_]
”Impressions of the more common plants found in the rocks of this period with sections of the tree trunks showing the woody structure will be [have been] introduced into the group as the ground on which the skeletons stand. In the rivers and bayous of that remote period there also lived many kinds of Unios or fresh-water clams, and other sh.e.l.ls, the casts of which are frequently found with Trachodon bones.
The fossil trunk of a coniferous tree was found in Wyoming, which was filled with groups of wood-living sh.e.l.ls similar to the living Teredo.
These also will be introduced in the ground-work.
”The skeleton mounted in a feeding posture was one of the princ.i.p.al specimens in the Cope Collection, which, through the generosity of the late President Jesup, was purchased and given to the American Museum.
It was found near the Moreau River, north of the Black Hills, South Dakota, in 1882, by Dr. J.L. Wortman and Mr. R.S. Hill, collectors for Professor Cope. The erect skeleton came from Crooked Creek, central Montana, and was found by a ranchman, Mr. Oscar Hunter, while riding through the bad lands with a companion in 1904. The specimen was partly exposed, with backbone and ribs united in position. The parts that were weathered out are much lighter in color than the other bones. Their large size caused some discussion between the ranchmen and to settle the question, Mr. Hunter dismounted and kicked off all the tops of the vertebrae and rib-heads above ground, thereby proving by their brittle nature that they were stone and not buffalo bones as the other man contended. The proof was certainly conclusive, but it was extremely exasperating to the subsequent collectors. Another ranchman, Mr. Alfred Sensiba, heard of the find and knowing that it was valuable 'traded' Mr. Hunter a six-shooter for his interest in it.
The specimen was purchased from Messrs. Sensiba Brothers and excavated by the American Museum in 1906.”
[Ill.u.s.tration: Fig. 30.--THE DINOSAUR MUMMY. SKELETON OF A TRACHODON PRESERVING THE SKIN IMPRESSIONS OVER A LARGE PART OF THE BODY. _After Osborn_]
THE DINOSAUR ”MUMMY.”
We all _believe_ that the Dinosaurs existed. But to realize it is not so easy. Even with the help of the mounted skeletons and restorations, they are somewhat unreal and shadowy beings in the minds of most of us. But this ”dinosaur mummy” sprawling on his back and covered with shrunken skin--a real specimen, not restored in any part--brings home the reality of this ancient world even as the mummy of an ancient Egyptian brings home to us the reality of the world of the Pharaohs.
The description of this unique skeleton by Professor Henry Fairfield Osborn first appeared in the Museum Journal for January 1911.[17]
”Two years ago (1908) through the Jesup Fund, the Museum came into possession of a most unique specimen discovered in August 1908, by the veteran fossil hunter Charles H. Sternberg of Kansas. It is a large herbivorous dinosaur of the closing period of the Age of Reptiles and is known to palaeontologists as _Trachodon_ or more popularly as the 'duck-billed dinosaur.'
”The skeleton or hard parts of these very remarkable animals had been known for over forty years, and a few specimens of the epidermal covering, but it was not until the discovery of the Sternberg specimen that a complete knowledge of the outer covering of these dinosaurs was gained. It appears probable that in a number of cases these priceless skin impressions were mostly destroyed in removing the fossil specimens from their surroundings because the explorers were not expecting to find anything of the kind. Altogether seven specimens have been discovered in which these delicate skin impressions were partly preserved, but the 'Trachodon mummy' far surpa.s.ses all the others, as it yields a nearly complete picture of the outer covering.
”The reason the Sternberg specimen (_Trachodon annectens_) may be known as a dinosaur 'mummy' is that in all the parts of the animal which are preserved (_i.e._ all except the hind limbs and the tail), the epidermis is shrunken around the limbs, tightly drawn along the bony surfaces, and contracted like a great curtain below the chest area. This condition of the epidermis suggests the following theory of the deposition and preservation of this wonderful specimen, namely: that after dying a natural death the animal was not attacked or preyed upon by its enemies, and the body lay exposed to the sun entirely undisturbed for a long time, perhaps upon a broad sand flat of a stream in the low-water stage; the muscles and viscera thus became completely dehydrated, or desiccated by the action of the sun, the epidermis shrank around the limbs, was tightly drawn down along all the bony surfaces, and became hardened and leathery, on the abdominal surfaces the epidermis was certainly drawn within the body cavity, while it was thrown into creases and folds along the sides of the body owing to the shrinkage of the tissues within. At the termination of a possible low-water season during which these processes of desiccation took place, the 'mummy' may have been caught in a sudden flood, carried down the stream and rapidly buried in a bed of fine river sand intermingled with sufficient elements of clay to take a perfect cast or mold of all the epidermal markings before any of the epidermal tissues had time to soften under the solvent action of the water. In this way the markings were indicated with absolute distinctness, ...
the visitor will be able by the use of the hand gla.s.s to study even the finer details of the pattern, although of course there is no trace either of the epidermis itself, which has entirely disappeared, or of the pigmentation or coloring, if such existed.
”Although attaining a height of fifteen to sixteen feet the trachodons were not covered with scales or a bony protecting armature, but with dermal tubercles of relatively small size, which varied in shape and arrangement in different species, and not improbably a.s.sociated with this varied epidermal pattern there was a varied color pattern. The theory of a color pattern is based chiefly upon the fact that the larger tubercles concentrate and become more numerous on all those portions of the body exposed to the sun, that is, on the outer surfaces of the fore and hind limbs, and appear to increase also along the sides of the body and to be more concentrated on the back. On the less exposed areas, the under side of the body and the inner sides of the limbs, the smaller tubercles are more numerous, the larger tubercles being reduced to small irregularly arranged patches. From a.n.a.logy with existing lizards and snakes we may suppose, therefore, that the trachodons presented a darker appearance when seen from the back and a lighter appearance when seen from the front.
[Ill.u.s.tration: Fig. 31.--The Dinosaur Mummy. Detail of skin of under side of body. _After Osborn_]
[Ill.u.s.tration: Fig. 32.--Skin impression from the tail of a _Trachodon_. The impressions appear to have been left by h.o.r.n.y scutes or scales, not overlapping like the scales on the body of most modern reptiles, but more like the scutes on the head of a lizard.]
[Ill.u.s.tration: Fig. 33.--Skull of Gila Monster (_Heloderma_), for comparison of surface with skin impressions of _Trachodon_.
Enlarged to 4/3.]
”The thin character of the epidermis as revealed by this specimen favors also the theory that these animals spent a large part of their time in the water, which theory is strengthened by the fact that the diminutive fore limb terminates not in claws or hoofs, but in a broad extension of the skin, reaching beyond the fingers and forming a kind of paddle.[18] The marginal web which connects all the fingers with each other, together with the fact that the lower side of the fore limb is as delicate in its epidermal structure as the upper, certainly tends to support the theory of the swimming rather than the walking or terrestrial function of this fore paddle as indicated in the accompanying preliminary restoration that was made by Charles R.
Knight working under the writer's direction. One is drawn in the conventional bipedal or standing posture while the other is in a quadrupedal pose or walking position, sustaining or balancing the fore part of the body on a muddy surface with its fore feet. In the distant water a large number of animals are disporting themselves.
”The designation of these animals as the 'duck-billed' dinosaurs in reference to the broadening of the beak, has long been considered in connection with the theory of aquatic habitat. The conversion of the fore limb into a sort of paddle, as evidenced by the Sternberg specimen, strengthens this theory.
”This truly wonderful specimen, therefore, nearly doubles our previous insight into the habits and life of a very remarkable group of reptiles.”
_Saurolophus, Corythosaurus._ In the latest Cretaceous formation, the Lance or Triceratops beds, all the duck-billed dinosaurs are much alike, and are referred to the single genus _Trachodon_. In somewhat older formations of the Cretacic period there were several different kinds. _Saurolophus_ has a high bony spine rising from the top of the skull; in _Corythosaurus_ there is a thin high crest like the crown of a ca.s.sowary on top of the skull, and the muzzle is short and small giving a very peculiar aspect to the head. Complete skeletons of these two genera are exhibited in the Dinosaur Hall; the _Corythosaurus_ is worthy of careful study, as the skin of the body, hind limbs and tail, the ossified tendons, and even the impressions of the muscular tissues in parts of the body and tail, are more or less clearly indicated.