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.
[Ill.u.s.tration: Fig. 34.--SKELETON OF SAUROLOPHUS, FROM UPPER CRETACIC OF ALBERTA. _After Brown_]
These Duck-billed Dinosaurs probably ranged all over North America and the northerly portions of the Old World during the later Cretacic.
Fragmentary remains have been found in New Jersey and southward along the Atlantic coast. A partial skeleton was described many years ago by Leidy under the name of _Hadrosaurus_ and restored and mounted in the museum of the Philadelphia Academy of Sciences. _Telmatosaurus_ of the Gosau formation in Austria also belongs to this group, and fragmentary remains have been found in the upper Cretacic of Belgium, England and France.
FOOTNOTES:
[Footnote 16: Brown, Barnum. "The Trachodon Group." Amer. Mus. Jour.
Vol. viii, pp. 51-56, plate and 3 text figs., 1908.]
[Footnote 17: Osborn, Henry Fairfield, "Dinosaur Mummy" Amer. Mus.
Jour. Vol. xi, pp. 7-11, ill.u.s.trated, Jan. 1911.]
[Footnote 18: There is some doubt whether this was really the condition during life. W.D.M.]
CHAPTER VIII.
THE BEAKED DINOSAURS (Continued.)
C. THE ARMORED DINOSAURS--STEGOSAURUS, ANKYLOSAURUS.
_Sub-Order Stegosauria._
This group of dinosaurs is most remarkable for the ma.s.sive bony armor plates, crests or spines covering the body and tail. They were more or less completely quadrupedal instead of bipedal, with straight post-like limbs and short rounded hoofed feet adapted to support the weight of the ma.s.sive body and heavy armature. Although so different superficially from the bird-footed biped Iguanodonts they are evidently related to them, for the teeth are similar, and the h.o.r.n.y beak, the construction of the pelvis, the three-toed hind foot and four-toed front foot all betray relationship. From what we know of them it seems probable that they evolved from Iguanodont ancestors, developing the bony armor as a protection against the attacks of carnivorous dinosaurs, and modifying the proportions of limbs and feet to enable them to support its weight. They were evidently herbivorous and some of them of gigantic size. Smaller kinds with less ma.s.sive armor have been found in Europe but the largest and most extraordinary members of this strange race are from North America.
STEGOSAURUS.
This extraordinary reptile equalled the Allosaurus in size, and bore along the crest of the back a double row of enormous bony plates projecting upward and somewhat outward alternately to one side and the other. The largest of these plates situated just back of the pelvis were over two feet high, two and a half long, thinning out from a base four inches thick. The tail was armed with four or more stout spines two feet long and five or six inches thick at the base. In the neck region and probably elsewhere the skin had numerous small bony nodules and some larger ones imbedded in its substance or protecting its surface. The head was absurdly small for so huge an animal, and the stiff thick tail projected backward but was not long enough to reach the ground. The hind limbs are very long and straight, the fore limbs relatively short, and the short high arched back and extremely deep and compressed body served to exaggerate the height and prominence of the great plates. The surface of these plates, covered with a network of blood-vessels, shows that they bore a covering of thick h.o.r.n.y skin during life, which probably projected as a ridge beyond their edges and still further increased their size. The spines of the tail, also, were probably cased in horn.
This extraordinary animal was a contemporary of the Brontosaurus and Allosaurus, and its discovery was one of the great achievements of the late Professor Marsh. The skeletons which he described are mounted in the Yale and National Museums. Another skeleton was found in the famous Bone-Cabin Quarry, near Medicine Bow, Wyoming, by the American Museum Expedition of 1901. This skeleton, at present withdrawn from lack of s.p.a.ce, will be mounted in the Jura.s.sic Dinosaur Hall in the new wing now under construction.
[Ill.u.s.tration: Fig. 35.--Skull and lower jaw of Armored Dinosaur _Ankylosaurus_, from Upper Cretacic (Edmonton formation) of Alberta. Left side view. _After Brown_]
ANKYLOSAURUS.
Related to _Stegosaurus_, equally huge, but very different in proportions and character of its armor was the Ankylosaurus of the late Cretacic. This animal, a contemporary of the Tyrannosaurus and duck-billed dinosaurs was more effectively though less grotesquely armored than its more ancient relative. The body is covered with ma.s.sive bony plates set close together and lying flat over the surface from head to tip of tail. While the stegosaur"s body was narrow and compressed, in this animal it is exceptionally broad and the wide spreading ribs are coossified with the vertebrae, making a very solid support for the transverse rows of armor plates. The head is broad triangular, flat topped and solidly armored, the plates consolidated with the surface of the skull and overhanging sides and front, the nostrils and eyes overhung by plates and bosses of bone; and the tail ended in a blunt heavy club of ma.s.sive plates consolidated to each other and to the tip of the tail vertebrae. The legs were short, ma.s.sive and straight, ending probably in elephant-like feet. The animal has well been called "the most ponderous animated citadel the world has ever seen" and we may suppose that when it tucked in its legs and settled down on the surface it would be proof even against the attacks of the terrible Tyrannosaur.
[Ill.u.s.tration: Fig. 36.--_Ankylosaurus_, top view of skull in fig.
35. _After Brown_]
This marvellous animal was made known to science by the discoveries of the Museum parties in Montana and Alberta under Barnum Brown.
Fragmentary remains of smaller relatives had been discovered by earlier explorers but nothing that gave any adequate notion of its character or gigantic size. From a partial skeleton discovered in the h.e.l.l Creek beds of Montana, and others in the Edmonton and Belly River formations of the Red Deer River, Alberta, it has been possible to reconstruct the entire skeleton of the animal, save for the feet, and to locate and arrange most of the armor plates exactly. A skeleton mount from these specimens will shortly be constructed for the Cretaceous Dinosaur Hall.
_Scelidosaurus, Polacanthus, etc._ Various armored dinosaurs, of smaller size and less heavily plated, have been described from the Jura.s.sic, Comanchic and Cretacic formations of Europe. The best known are _Scelidosaurus_ of the Lower Jura.s.sic of England, and _Polacanthus_ of the Comanchic (Wealden). _Stegopelta_ of the Cretaceous of Wyoming is more nearly related to _Ankylosaurus_.