Palaeotherium

“ Palæotherium and the allied genus Paloplotherium, were abundant in France and England in Upper Eocene times. They somewhat resembled the tapir, with affinities for the horse and rhinoceros. A new genus, Cadurcotherium, allied to the rhinoceros and equally large, has been found in the same deposits of phosphate of lime as the lemur and Ælurogale. In the Middle Eocene of both England and France are found Lophiodon allied to the tapir, but in some of the species reaching a larger size; Propalæotherium and Pachynolophus of smaller size and having affinities for the other genera named ”

“ Murchison have discovered, at Georgensgemünd, in Bavaria, the bones of Palæotherium, Anoplotherinm, and Anthracotherium, mixed with those of Mastodon, Rhinoceros, Hippotamus, Horse, Ox, Bear, Fox, &c.; and several species of land shells. A very interesting detailed description of the remains found at this place has been published by Hermann von Meyer, Frankfurt, 1834, 4to. ”

“ We may add, as further examples, the names of the various animals of which a knowledge has been acquired from the remains of them which exist in various strata, and which have been reconstructed by Cuvier and his successors. Such are the Palæotherium, the Anoplotherium, the Megatherium, the Dinotherium, the Chirotherium, the Megalichthys, the Mastodon, the Ichthyosaurus, the Plesiosaurus, the Pterodactylus. To these others are every year added; as, for instance, very recently, the Toxodon, Zeuglodon, and Phascolotherium of Mr. Owen, and the Thylacotherium of M. Valenciennes. ”

“ Leidy describes a gigantic quadruped, called by him Titanotherium, nearly allied to the Palæotherium, but larger than any of the species found in the Paris gypsum. With these are several species of the genus Oreodon, Leidy, uniting the characters of pachyderms and ruminants also; Eucrotaphus, another new genus of the same mixed character; two species of rhinoceros of the sub-genus Acerotherium, a Lower Miocene form of Europe before mentioned; two species of Archæotherium, a pachyderm allied to Chæropotamus and Hyracotherium; also Pæbrotherium, an extinct ruminant allied to Dorcatherium, Kaup ”

“ Another remarkable animal restored by the great French palæontologist, the Palæotherium, similarly tended to connect together animals to all appearance so different as the rhinoceros, the horse, and the tapir. Subsequent research has brought to light multitudes of facts of the same order; and, at the present day, the investigations of such anatomists as Rütimeyer and Gaudry have tended to fill up, more and more, the gaps in our existing series of mammals, and to connect groups formerly thought to be distinct. ”

“ The Mastodons, the Palæotherium, the Dinotherium, and other large Mammalia of the Tertiaries, are closely related to the Tapir. The elephant, rhinoceros, and the like, are of the same family. From its structural standing next to the elephant, which is placed highest in the group, the embryology of the Tapir would give us a very complete series of changes. It would seem from some of the fossil remains of this family that the Pachyderms were formerly more nearly related to the Ruminants and Rodents than they now are. ”

“ Miocene America is scarcely behind the Old World in the development of its land animals. From one locality in Nebraska, Leidy described in 1852 fifteen species of large quadrupeds; and the number has since been considerably increased. Among these are species of Rhinoceros, Palæotherium, and Machairodus; and one animal, the Titanotherium, allied to the European Anoplothere, is said to have attained a length of eighteen feet and a height of nine, its jaws alone being five feet long. ”

“ The orbit is completely open behind. In other respects the palaeotheres resemble the ancestral horses. They were, however, essentially marsh-dwelling animals, and exhibit no tendency to the cursorial type of limb so characteristic of the horse-line. ”

“ In the lower, or Wasatch, Eocene the group was represented by the still more primitive Lambdotherium. On the other hand, Palaeosyops is connected with Titanotherium by means of Telmatotherium of the upper Bridger and Washakia Eocene, a larger animal, with a longer and flatter skull, showing rudiments of horn-cores, only two pairs of lower incisors, and a general approximation in dental character to Titanotherium. Another of these titanotheroid forms is Diplacodon, from the Upper or Uinta Eocene; an animal the size of a rhinoceros, with the last two upper premolars molar-like. ”

“ By similar and not more violent changes we pass easily to such allied forms as the Titanotheres (Fig. 397) ; and the well-known series of species of Titanotherium, by which Professor Osborn has {763} illustrated the evolution of this genus, constitutes a simple and suitable case for the application of our method.
But our method enables us to pass over greater gaps than these, and to discern the general, and to a very large extent even the detailed, resemblances between the skull of the rhinoceros and those of the tapir or the horse. ”

“ I think that this desideratum is very nearly, if not quite, supplied by Plagiolophus, remains of which occur abundantly in some parts of the Upper and Middle Eocene formations. The patterns of the grinding-teeth of Plagiolophus are similar to those of Anchitherium, and their crowns are as thinly covered with cement; but the grinders diminish in size forwards, and the last lower molar has a large hind lobe, convex outwards and concave inwards, as in Palueotherium. The ulna is complete and much larger than in any of the Equidoe, while it is more slender than in most of the true Paloeotheria ”

“ In the chapter on Geology we called attention to the fact that the Paleotherium appeared before the Horse, etc. The embryo Plorse, however, in his three toes and the structure of his teeth, represents the Paleotherium (Fig. 154) , while the transitory stages through which the Horse passes from the Paleotheroid condition to its adult state are permanently retained in the Anchitherium and Hipparion. (Fig. 155) . In Ruminating animals, like the Gazelle, Sheep, and Ox, the upper jaw is without incisor and canine teeth (Fig. 157) ”

“ Hermann von Meyer observes, afford no sure criterion of antiquity, for they have been observed on Roman bones. Nevertheless, they are more common in bones that have been long embedded in the earth. The skull and bones, moreover, of the Neanderthal skeleton had lost so much of their animal matter as to adhere strongly to the tongue, agreeing in this respect with the ordinary condition of fossil remains of the post-pliocene period. On the whole, I think it probable that this fossil may be of about the same age as those found by Schmerling in the Liége caverns ”

“ The largest species of dinotherium lived in Pliocene time and rivaled in size the mastodon and mammoth. The skulls of this genus are found quite abundantly in the Miocene deposits of central Europe, in the Lower Pliocene of India and the Upper Pliocene of Greece, and are often associated with remains of the rhinoceros. No dinotherium remains have yet been found in America. ”

“ The bone expands towards its distal end, which corresponds in structure with those of the two lateral metatarsals in the fore-foot, in being completely divided into two trochlear surfaces by a well-developed median ridge, and in having the posterior half of this ridge suddenly produced, so as to project about two lines further from the trochlear surface than the anterior part of the same ridge. In both the Tapir and Palæothere this anterior part of the ridge is wholly suppressed, and the posterior is much more feebly developed than in the Macrauchenia. ”

“ The skulls of Asiatherium and Sinodelphys are relatively crushed, making reconstruction problematic. Extant didelphid marsupials and some early Paleocene taxa retain many plesiomorphic therian features and their skulls closely resemble the limited fossil cranial material of Cretaceous metatherians in many respects, meaning that they can be used as a guide for reconstructing Cretaceous metatherian skull morphology ( [122] , [124] ; [125] ) (Fig. 8) . ”

“ The divisions in the fossil record having been thus established, they must for convenience remain, but their artificially cannot be too strongly emphasized, for the broad stratigraphical gaps and lithological groups which made the divisions sharp and clear to the earlier geologists are proved to be absent in other regions, and fossils which were formerly deemed characteristic of the Palaeozoic era are found in some places to commingle with forms of strongly marked Mesozoic type. ”

“ It was provisionally assigned to Deltatheroida by Szalay and Trofimov, but other workers (e.g., [2] ; [11] ) have found it to be near the base of Marsupialiformes and possibly related to stagodontids. Partial skulls are known for several Late Cretaceous metatherian taxa, including the Asian deltatheroidans Deltatheridium and Sulestes ( [2] ; [11] ) . Although metatherians were more species rich and evidently numerically abundant in the Late Cretaceous of North America relative to Asia (at least based on the known fossil record) , the North American specimens are more fragmentary. ”

“ I will now sum up the results of this sketch of the rise and progress of palaeontology. The whole fabric of palaeontology is based upon two propositions: the first is, that fossils are the remains of animals and plants; and the second is, that the stratified rocks in which they are found are sedimentary deposits; and each of these propositions is founded upon the same axiom, that like effects imply like causes. If there is any cause competent to produce a fossil stem, or shell, or bone, except a living being, then palaeontology has no foundation ”

“ For long decades, vertebrate paleontology was simply a branch of comparative anatomy or morphology in that it dealt almost exclusively with the form and other peculiarities of fossil bones and teeth, often in a more or less fragmentary condition, very little or no attention being paid to any other system of the creature’s anatomy. Distribution both in space and in time was recorded, but the value of vertebrates in stratigraphy was still to be appreciated and has hardly yet come into its own. ”

“ In comparing the older with the more recent forms it is noteworthy that there has been an increase of size exactly as there has been during the evolution of the Camels and some other groups of Ungulates. As already mentioned, the size of the horn cores also increases until it culminates in the extraordinary species, T. platyceras and T. ramosum, in which these are half as long as the skull, flattened in form, and connected at their bases by a "web" of bone. Arrived at this amount of specialisation the genus Titanotherium apparently exhausted its capacities for modification and ceased to be. ”

“ Reconstructing the postures, locomotor abilities, and habitat preferences of most fossil metatherians is exceedingly difficult, because most extinct taxa are known only from isolated jaws and teeth. Nevertheless, the rare postcranial fossils of Cretaceous metatherians give some insight into their locomotory paleobiology. The small skeleton of the oldest recognized metatherian, Sinodelphys, possesses features seen in living mammals that climb, leading [9] to hypothesize that it was scansorial and possibly arboreal. ”

“ Paleozoic time, although shorter than the pre-Cambrian as measured by the thickness of the strata, must still be reckoned in millions of years. During this vast reach of time the changes in organisms were very great. It is according to the successive stages in the advance of life that the Paleozoic formations are arranged in five systems,—the CAMBRIAN, the ORDOVICIAN, the SILURIAN, the DEVONIAN, and the CARBONIFEROUS. On the same basis the first three systems are grouped together as the older Paleozoic, because they alike are characterized by the dominance of the invertebrates ”

“ So that just as the Rhinoceros and Horse are specialized forms of the Paleotherium, the Pig and Sheep of the Anoplotherium, so the Paleotherium and Anoplotherium are specialized forms of the Coryphodon. Accepting the theory of the specialized higher forms of life having descended from a more general lower form, we have an explanation of the harmony offered by the anatomy, embryology, and petrified remains of these animals. ”

“ Metatherians are a clade of boreosphendian mammals that must have originated by the Late Jurassic, but the first unequivocal metatherian fossil is from the Early Cretaceous of Asia. Metatherians have the distinctive tightly interlocking occlusal molar pattern of tribosphenic mammals, but differ from Eutheria in their dental formula and tooth replacement pattern, which may be related to the metatherian reproductive process which includes an extended period of lactation followed by birth of extremely altricial young. ”

“ Because of the pervasiveness of sampling bias, it is very difficult to rigorously study how metatherians were distributed across the Cretaceous globe and how intercontinental dispersals and continental breakup may have affected their evolution. Many previous authors have proposed complex, and in some cases grand, biogeographic narratives based on very limited fossil evidence, sometimes the discovery of a single new tooth. Such scenarios are tempting to consider, but exceedingly difficult to test. ”

“ In the Megatherium, the roots of the five superior molars are all situated behind the anterior boundary of the orbit: in the Orycteropus, on the contrary, the grinders are all placed in advance of the orbit; so that the Scelidothere resembles that species more than the Megathere in the relative location of the teeth. The palatal interspace between the roots of the last molar tooth of each series is eleven lines ”