Popular Science Monthly/Volume 67/October 1905/Western Explorations for Fossil Vertebrates

From Wikisource
Jump to navigation Jump to search

WESTERN EXPLORATIONS FOR FOSSIL VERTEBRATES.
By Dr. HENRY FAIRFIELD OSBORN,

GEOLOGIST AND PALEONTOLOGIST, U. S. GEOLOGICAL SURVEY.

OWING to the establishment of new natural history museums in different parts of the United States, western exploration for the past history of the reptilian and mammalian life of North America is becoming more active and energetic every year. Formerly (between 1869 and 1877) the only explorations of this character were conducted by Professor Cope, of Philadelphia, one of the ablest zoologists and anatomists this country has produced, and by the still more widely known Professor Marsh, of Yale College. The fossils came in so rapidly that, while rousing keen scientific interest, they could not be placed on exhibition for the benefit of the public. In 1877 Princeton College began its series of western trips under Professor Scott and the present writer. Then Kansas University, under the able leadership of Professor S. W. Williston, went actively into the field, chiefly in the old Cretaceous sea bottom of western Kansas.

In 1890 the American Museum of Natural History of New York paved the way for a new order of things, by initiating a series of explorations on a large scale into different regions of the west, and placing the fossils on public exhibition as rapidly as possible.

The next comer was the Carnegie Museum of Pittsburgh, which, under the active direction of Dr. Holland, secured as a leader Dr. J. L. Wortman, who had proved his unusual abilities in this line, first by his wonderful discoveries in the Big Horn Mountains in northern Wyoming and elsewhere in the service of Professor Cope, and later in the service of the American Museum of Natural History. The work of the Carnegie Museum, however, soon passed into the hands of Mr. J. B. Hatcher, another explorer of the highest ability, who had previously gained a world-wide reputation by his exploration of the fossil beds of Patagonia in the interests of Princeton. The death of Mr. Hatcher during the summer of 1904 was a very great blow to American paleontology. Under Wortman, Hatcher and Peterson the collections at the Carnegie Museum have grown apace, and the museum now has an almost unique collection of the gigantic amphibious dinosaurs, reptiles from fifty to eighty feet in length, which inhabited the shore lines of the nascent Rocky Mountains in the. Jurassic period. When the new portion of this great museum is completed and sufficient space is provided, it is proposed to mount some of these great animals complete. In the meantime Mr. Carnegie has ordered a cast of one of the finest specimens (Diplodocus carnegiei) to be presented to the British Natural History Museum in London, where this cast is now mounted. Not content with these monster reptiles, the Carnegie Museum has sent out other expeditions, for fossil horses, camels, titanotheres, and other quadrupeds and carnivores which formerly inhabited the now desert regions of South Dakota and Wyoming.

PSM V67 D568 John Bell Hatcher.png

The Late John Bell Hatcher.

A year or so after, the Carnegie Museum and the Field Columbian Museum of Chicago instituted a series of annual expeditions, chiefly for the great amphibious dinosaurs found in Wyoming and Colorado. Under Dr. E. S. Riggs some remarkable discoveries have been made, most notable of which is a nearly complete skeleton of Brontosaurus in a fine state of preservation. In central Colorado were found the arm bone, or humerus, and thigh bone, or femur, of another reptile of the same group of still more gigantic size. In most of these dinosaurs the femur is decidedly longer than the humerus; but in this beast, although the femur is actually 6 feet 8 inches in length, the humerus is fully as long. Dr. Riggs has accordingly named this animal Brachiosaurus, in reference to the great size of the brachium, or arm.

PSM V67 D569 Restoration of the diplodocus carnegii.png

Restoration of the Diplocodus carnegii, by J. B. Hathcer.

There is naturally a strong feeling in the far west that some of these remarkable fossils should be kept nearer home and not continually be the subject of eastern enterprise. Accordingly, the University of Wyoming, situated at Laramie, under the active leadership of the late Professor Wilbur C. Knight, for many years sent out expeditions, chiefly into various parts of the great state of Wyoming. These also were highly successful in securing remains of the amphibious dinosaurs, also of the great long-necked marine reptiles of the order Plesiosauria. To one specimen of the latter type, distinguished by a swimming paddle 7 feet 4 inches in length, Professor Knight gave the name of Megalneusaurus rex. Unfortunately we have to record the death of this ardent naturalist and indefatigable explorer, who made up in energy and personal hard work what the university lacked in financial resources.

We have to add also the University of California to the ranks of exploring institutions. Professor James Perrin Smith and Professor J. C. Merriam explored in 1895 and 1901, 1902, 1903 the bottom of an ancient inlet of the sea, of triassic age, in which are deposited the remains of very peculiar types of ichthyosaurs. These have been described by 1 Professor Merriam, who has appropriately given them the name Shastosaurus, in reference to the proximity of the beds in which they occur to Mt. Shasta. These reptiles are in general distinguished from the plesiosaurs by the dolphin like form of the body and the like tail, smooth, scaleless skin, very effective, dolphin-like paddles, and long, pointed snout. Dr. Merriam at first regarded Shastosaurus as a segregated or isolated type which developed from some more primitive ichthyosaur stock in this ancient bay of the Pacific; but his more thorough study and the additional materials collected during 1903 have revealed a very interesting fact, namely, that these animals are closely related to a species discovered long before by an English paleontologist, Professor Hulke, and named by him Ichthyosaurus polaris. The demonstration of the identity of this Pacific and extreme north Atlantic form speaks for the continuity of the Pacific and Atlantic oceans in triassic times, and is a fact of interest to geographers as well as to zoologists.

Dr. F. B. Loomis, of Amherst, who also spent two seasons with American Museum parties, has begun what we may hope will prove to be a series an annual expeditions in behalf of Amherst College. He took his students in 1903 into western Dakota to the 'Titanothere' and 'Oreodon' beds, and secured what is reported to be a very fine collection. In 1904 he conducted an exploration into the Wind River Eocene of northern Wyoming, discovering a special deposit of Lower and Middle Eocene fossils in this rather barren horizon. At Amherst College is the remarkable collection made by the elder Professor Hitchcock of fossil footprints found along the Connecticut River, which were at first attributed to birds, but are now known to have been made by (dinosaurs. Professor Lull, of the Massachusetts College of Agriculture, has been restudying these tracks and has drawn from them some remarkable conclusions as to the mode of life of these ancient denizens of Connecticut, which have been published in the form of a memoir by the Boston Society of Natural History. Professor Lull has also been attached to the American Museum expeditions as a successful field worker.

The American Museum of Natural History has by no means been inactive during the years 1903 and 1904, having sent out no less than four expeditions, which together have secured two large freight carloads of fossils.

The first of the expeditions in 1903, under Mr. J. W. Gidley, was especially searching for the fossil ancestry of the horse in western Nebraska and on the Rosebud and Indian Agency in South Dakota, where a permit was secured. Here the bed of an ancient washout or local flood was discovered containing the remains of a variety of threefoed horses of Upper Miocene age belonging to several species of the genera Protohippus and Neohipparion. No complete skeleton was discovered, but these horses supplement the series found in previous years, and demonstrate one fact of great interest, namely, the coexistence in western America of at least three entirely distinct kinds of three-toed horses, including (1) those with excessively light, almost deerlike limbs; (2) others with shorter, more robust limbs, less specialized and leading apparently into the true modern horse; (3) others again, forest living forms, with spreading side toes, perhaps designed to prevent the animals from sinking into the soft ground of the swampy regions which they may have inhabited. Here also was found the complete skeleton of the camel, Camelus occidentalis, of mastodons, and of several other new types of animals, especially the wolves and foxes of the period.

Another American Museum expedition worked its way into the waterless desert in western South Dakota, where, in the bed of an

PSM V67 D571 Skeleton of the neohipparion whitneyi.png

Complete Mounted Skeleton of the Neohipparion whitneyi, A Three Toed Horse of the Upper Miocene Epoch. In the American Museum of Natural History.

ancient inlet of the sea, perhaps ten million years ago, were deposited the skeletons of two well-known varieties of sea reptiles, mosasaurs and plesiosaurs. These were found encased like mummies in a soft rock imbedded in larger concretions which stood up like mushrooms in what the westerners called a 'blow-out.' Numerous skeletons were found in a beautiful state of preservation, and formed the chief feature of this expedition. Just as Mr. Barnum Brown, the head of this party, was on his way east, a telegraphic order directed him into northwestern Arkansas to a comparatively recent deposit, perhaps 200,000 years of age, made just prior to the glacial period. It recorded chiefly the small western preglacial fauna, the field mice, shrews, minks, badgers, rabbits, ancestors of familiar living western types, mingled, however, with remains

PSM V67 D572 Fossil bones of the great brachiosaurus altithorax.png

Fossil Bones of the Great Brachiosaurus allithorax, before Removal from the Rock. After E. S. Riggs

of camels, horses and of the great sabre-toothed tiger. This was a great fissure deposit, into which enormous numbers of these small animals had been washed, so the collection was numerically very large. It is an interesting but not surprising fact that this small fauna survived the subsequent glacial period, whereas the horses, sloths, camels and saber-toothed tigers were all exterminated.

PSM V67 D572 Bone cabin quarry south central wyoming.png

The Bone Cabin Quarry. South Central Wyoming. Fossilized bones of many different kinds of the great amphibious dinosaurs, of the plated dinosaurs (Stegosaurs), of the large carnivorous dinosaurs and of the small carnivorous dinosaurs are found mingled together in this quarry.

A third American Museum party was in the heart of the Laramie plains of Wyoming, where in 1898 the ruins of a sheep herder's cabin composed entirely of dinosaur bones led to the discovery of an extraordinarily rich deposit of the great amphibious dinosaurs and other reptiles of the Upper Jurassic age, which is roughly estimated as 6,000,000 years distant. The museum has been working in this same quarry six years, and each year has taken out a very large freight carload, yet the deposit is still far from being exhausted.

PSM V67 D573 Stratified deposits in the bridger basin southwestern wyoming.png

Stratified Deposits in the Bridger Basin, Southwestern Wyoming.

A fourth expedition was in southwest Wyoming, just north of the Uintah Mountains, nor far from the once famous Fort Bridger, a now deserted army post. This middle eocene flood plain or lake basin dates back about 2,500,000 years in its fauna, which embraces small ancestors of the horses, about the size of a whippet hound, a great variety of monkeys, hundreds of small quadrupeds remotely related to the tapirs, including one especially large type. Also of the great Uintatherium or Uinta beast, a very archaic type of quadruped, the discovery of which between 1870 and 1873 aroused widespread interest in this country. The museum party was very fortunate also in this region and brought back remains of about five hundred individuals. In this collection were one hundred and twenty-one turtles, chiefly found by Dr. O. P. Hay, both river and land forms, some ancient, some surprisingly modern in type, including species which are now only represented in South America.

During the summer of 1904 three expeditions went out from the American Museum, the first in charge of Messrs. Matthew and Granger into southwestern Wyoming, making special search for additional remains of the great horned Uintatherium. They were rewarded by the discovery of two skeletons and a fine lower jaw. One of these skeletons was in such a position that it appeared to have been mired in what was at the time a soft, tenacious clay, but is now an olive shale. They also discovered two fine skulls of the primitive running rhinoceros, Hyrachyus, the skull and part of the skeleton of Hyopsodus, which has long figured as a lemur, but is now thought to be an insectivore; three skulls of the primitive tapir, Isectolophus; six skulls and portions of the skeleton of Palæosyops, and two skulls of carnivores. In spite of diligent search no additional remains were secured of the fossil horse of the Bridger. The most important general feature of this work, however, is the fact that the Bridger formation can now be definitely divided up into a series of great geological steps, A, B, C, D, each characterized by a distinct assemblage of animals or by distinct and different stages of evolution. The second American Museum party, under Mr. Brown, well known for his successful explorations in Patagonia and Montana, went out with the special object of securing a complete skeleton of some of the great plesiosaurs of the cretaceous. Continuing his work of 1902 and 1903, Mr. Brown made special search in the Pierre shales, securing near Edgemont, South Dakota, the greater part of the skeleton of a Plesiosaur, including skull, jaws, complete neck about fifteen feet long, one complete paddle, part of the pectoral girdle and some dorsal vertebræ. In the same locality another plesiosaur and several long snouted marine crocodiles were found.

In the museums which have been enriched by last season's explorations the work of preparation for exhibition and scientific description is progressing. It is, unfortunately, an extremely slow and difficult matter to prepare a fossil, however carefully collected, for exhibition. It takes two years or more to work out the collections of a single season; the result is that most of our museums are collecting materials more rapidly than they can be worked up; hundreds, and in some cases thousands, of boxes are stored away. With larger endowments or with special gifts these treasures could be more rapidly brought to light.

The popular interest in the ancient history of North America as shown in the rise and fall of the successive dynasties of animal life is rapidly increasing; the daily journals give a large amount of space to fresh discoveries—usually with a considerable amount of exaggeration. The animals in themselves are so wonderful, and the mere presence of representatives of South America, Africa, Asia and western Europe, in the Rocky Mountain region, appeals so strongly to the imagination, that the bare scientific facts are of sufficient interest without exaggeration.