OCR Text |
Show 1882.] PROF. W. H. FLOWER ON THE EDENTATA. 365 by the disappearance of the fcetal villi at the two poles of the ovum ; while the small size of the umbilical vesicle indicates that it is not, like the zonary placenta of the Carnivora, directly derived from a type with both allantoic and umbilical vascularization of the chorion. Although palaeontology has revealed the existence of a vast number of the Edentates by which the New World was tenanted in the Pleistocene age, and has given us a more perfect idea of their characters than is known of most other extinct forms, unfortunately the history of the group throughout the period of the true Tertiaries is at present almost a blank. The presence of a large species probably allied to Manis in the Siwalik fauna is indicated by a single phalanx, described and figured by Lydekker under the name of M. sindiensis. No animals, attributed with any certainty to the Edentata, are known of Eocene age. The few scattered and imperfect remains of supposed Edentates, Macrotherium and Ancylotherium, of the European later Miocene formations, and the similarly imperfect and as yet not fully described bones of Moropus and Morotherium of corresponding ages in North America, indicate that animals existed at that time of large size, presenting characters in some respects allied to the recent members of the order, but in others so different that they cannot be placed in any of the existing families. Macrotherium, for instance, appears to have limb-characters which ally it to the Ungulates. As far as can be surmised at present, the affinities of these early forms were rather with the existing members which survive in their own part of the world, than with those of a different hemisphere. Macrotherium certainly appears to present more resemblance to Manis than to the American Edentates. The first fragments of it which were found were attributed by Cuvier to a " Pangolin gigantesque." But some evidence has since been found in favour of its having possessed teeth. So far this is quite what might be expected; hut it certainly throws very little light either upon the mutual relations of the existing forms, the steps by which the present state of things has been brought about, or, what would be still more interesting, their affinities with mammals of other groups. The tabular form (see p. 3G6) into which the result of these inquiries have been thrown will show what I conceive to be the relationship of the existing forms ; but it also shows the great deficiency of our knowledge of the group in past ages. The general conclusions to which a study of this group have led me may be summed up as follows:-All the American Edentates at present known, however diversified in form and habits, belong to a common stock. The Bradypodida, Megatheriida, and Myrmeco-phagida are closely allied, the modifications seen in tbe existing families relating to food and manner of life. The ancestral forms may have been omnivorous, like the present Armadillos, and gradually separated into the purely vegetable and purely animal feeders ; from the former are developed the modern Sloths, from the latter the Anteaters. The Armadillos are another modification of the same type, retaining some more generalized characters, as those |