« AnteriorContinuar »
DISTRIBUTION OF EDENTATE MAMMALS
SECTION 1.—INTRODUCTORY REMARKS
As is the case with most ancient groups, we find the various types of Edentate Mammals strictly limited to certain localities on the earth's surface, so that the study of their distribution, especially when taken in connection with what we know of the extinct forms of the same group, comes to be a matter of much interest. In the present case, however, we propose to confine our remarks to the existing Edentates, as we are discussing the distribution of recent and not of fossil mammals, and merely to allude to the extinct forms when necessary.
As regards the existing Edentates, as has been well shown by one of our leading authorities on mammals, those of the Old World and those of the New are essentially distinct. The two Old World families commonly assigned to this order, are so different in important points of structure from the American families, that it may be even considered doubtful whether they were derived from the same primary branch of mammals. We will, therefore, take the two groups separately, and begin with the forms of the New World.
SECTION II.-DISTRIBUTION OF THE NEW WORLD
The Edentates of the New World are at present represented by three families, the Sloths (Bradypodidæ), the Ant-eaters (Myrmecophagidæ), and the Armadilloes (Dasypodide), all well distinguished from each other, although essentially modified on the same plan of structure, and more or less united together by other Edentates now extinct. All three families belong entirely to the Neotropical Region, although one of the Armadilloes appears to have intruded itself farther north than the generally recognized northern boundary of that Region.
Of the Sloths, two genera are well established-the Three-toed Sloths (Bradypus), with about five species, and the Two-toed Sloths (Cholopus), with two species. The Sloths are entirely arboreal in their habits, and are met with only in the dense forests of Central and Southern America, from Nicaragua down to Bolivia and Southern Brazil.
The Ant-eaters, of which three well-marked forms are known, belonging to so many genera, each with one species, have a somewhat wider distribution, being not absolutely confined to the tropical forests. The Great Ant-eater (Myrmecophaga jubata), extends as far north as Guatemala, and from Costa Rica southwards is found in suitable localities all through Venezuela, Guiana, and Brazil to Paraguay.
The Tamandua Ant-eater (Tamandua tetradactyla), which varies much in colour and markings, extends even farther north than its larger brother, as specimens have been obtained in Southern Mexico. Southwards it passes throughout South America as far as Paraguay, where Rengger assures us it is common, and widely distributed. The little Two-toed Ant-eater (Cyclothurus didactylus), a purely arboreal form, is also found in Guatemala, Nicaragua, and Costa Rica, but does not range so far south as the two former species, though it extends throughout the great Amazonian valley into Peru.
The Dasypodidae, or Armadilloes, which contain the third family of American Edentates, are more numerous and more diversified in their characters than the two preceding families. The eighteen or twenty species generally recognized by naturalists may be divided into four subfamilies and seven genera. The general area of their distribution is rather larger than that of the Sloths and Ant-eaters. One Armadillo, as has been already mentioned, goes as far north as Texas, and Armadilloes are found all over the Argentine Republic down to Patagonia.
The most remarkable of the Armadilloes, and one that must form a sub-family by itself, is the little Pichy-ciego of the Argentines (Chlamydophorus truncatus), which is found in the sandy plains of the vicinity of Mendoza, and also, as has been recently ascertained, near Bahia Blanca in the eastern part of the Argentine Republic. A second species of this genus, more recently discovered (C. retusus) is met with in Bolivia.
The typical Dasypodinæ, consisting of about eleven or twelve species divided among four genera, are distributed all over the area of the family, south of Panama, but do not range into Central America, so far as has hitherto been ascertained.
The Giant Kangaroo (Priodon gigas), which belongs to this sub-family, is the largest Armadillo known, measuring about three feet in the length of its body: it inhabits the forests of Guiana and Brazil. The three species of Tolypeutes, which have the power of rolling themselves up into a ball like a Woodlouse, are restricted to the pampas of Argentina and Bolivia. The members of the two other genera of Dasypodina (Dasypus and Xenurus) range from Guiana to Patagonia, but are mostly met with in the south.
Of the third sub-family (Tatusiinæ), distinguished from the rest of the group by the peculiar structure of the fore-feet, five species, all belonging to the genus Tatusia, are known. One of these, the Peba Armadillo, passes up through Central America into Texas, and is also widely distributed throughout South America down to Paraguay. Another species of this genus, T. hirsuta, distinguished by its thick covering of hair, occurs in Western Peru, and the remainder are found in different parts of South America.
The very curious Armadillo, described in 1872 by M. Milne-Edwards (Nouv. Arch. d. Mus., vii., p. 177, 1871) from an imperfect specimen as Scleropleura bruneti, is from the province of Ceara, North Brazil. It should apparently form a sub-family of itself.
SECTION III.-DISTRIBUTION OF THE OLD WORLD
The Old World mammals, placed in the Order of Edentates, perhaps more from the want of a better position for them than for any other reason, belong to two families -the Maniidæ, or Pangolins, and the Orycteropodida, or
Aard-Vaarks. Of the Pangolins about seven species are generally acknowledged by naturalists, of which three belong to the Oriental and four to the Ethiopian Region. The species of each region belong to different sections of the genus. The Oriental Section consists of the Javan Pangolin (Manis javanica), which ranges from Burma through the Malay Peninsula to Java and Borneo; the Chinese Pangolin (M. aurita) from China, Assam, and Nepal; and the Indian Pangolin (M. pentadactyla) of India and Ceylon. Of the four species of the African section only one (Temminck's Pangolin) occurs out of the West African Sub-region, extending into Eastern and Southern Africa. Finally we have the Orycteropodidæ, or AardVaarks, which comprehend only the single genus Orycteropus, with two species entirely restricted to the Ethiopian Region, and forming one of its most characteristic types of mammal-life.
SECTION IV.-SUMMARY AND DEDUCTIONS Table of the families and genera, showing the number of species in each Region.