The New International Encyclopædia/Holarctic Region
HOLARCTIC REGION (from Gk. ὅλος, holos, entire + ἀρκτικός, arktikos, northern, from ἄρκτος, arktos, bear). A division in zoögeography, defined in two senses: (1) Arctogæa. In the larger sense the term is used, unhappily, as a synonym for ‘Arctogæa.’ (See Distribution of Animals and Notogæa.) This ‘region’ embraces all of the Northern Hemisphere except the hot coast regions of Central America, all of Africa and Madagascar, and an indefinite extent of the Malayan and Polynesian islands, where its boundaries vary in different classes of animals; in other words, it is a combination of the Nearctic, Palæarctic, Palæotropical, and Oriental regions of Sclater and Wallace, as opposed to the combined Neotropical and Australasian regions (Notogæa). The fundamental difference between Arctogæa and Notogæa reaches back to an early geological period, while many of the present distinctions between their subdivisions disappear when traced back to the Tertiary, when the distribution of animal life was very different from now. It is this broad historical view, rather than the modern aspect, which has led naturalists to the generalizations of Arctogæa and Notogæa. Limiting the comparison to vertebrate animals, the characteristics of Arctogæa are in outline as follows: Among fishes, the perches, carps, salmons, and sturgeons are present as whole tribes, together with many lesser groups, especially of fresh-water or coast fishes, while the lungfishes are conspicuous absentees. In the class Amphibia, the line is drawn at the frog family Cystignathidæ, which is entirely Arctogæan. Gadow also points out the predominance of Arcifera, which constitute nine-tenths of the anurous population, and are hardly represented in Notogæa. Of turtles, the presence of Trionychoidea and the absence of Chelydidæ are distinctive. Of lizards, exclusively Arctogæal groups are the Lacertidæ, Zomoridæ, Gerrhosauridæ, and Aniellidæ. Among the snakes, the viper family is entirely Arctogæal, and the crotaline tribe mainly so. Lesser exclusive groups are the Uropeltidæ, Xenopeltidæ, and many genera. Ornithological distinctions may be most easily sketched by saying that Arctogæa possesses no emus or cassowaries; no mound-birds, birds of paradise, lyre-birds, cockatoos, tinamous, curassows, hoactzins, toucans, cotingas, or many others, although it is rich in game birds, finches, woodpeckers, wood-warblers, and the like. But perhaps the most striking difference is the presence of the large Arctic tribe of auks, and the like, and the absence of penguins. Among mammals, also, the most notable feature is the entire absence of edentates, of monotremes, of marsupials (except one opossum), of cebine monkeys, and of marmosets. The northern region, however, has the lemurs, the insectivores except the West Indian Solenodon, the elephants, rhinoceroses, hyraces, horses, deer, giraffes, bovines, hyenas, hares, and a variety of other important families; it is, in fact, as Beddard points out, the headquarters of all the Eutheria except edentates and marsupials.
(2) Holarctic, or Periarctic, Province. In a more restricted and perhaps more usual sense, the term ‘holarctic’ in zoögeography denotes a circumpolar district formed by the union of the Palæarctic and Nearctic provinces of Sclater and Wallace, elsewhere described. It was long ago felt that the faunal characteristics of North America and the northern part of the Old World were not sufficiently distinct to justify their separation into two provinces. Their union under one name was first made by A. Heilprin, who proposed ‘Triarctic’ as the new designation. For this A. Newton suggested the substitution of ‘Holarctic,’ which Heilprin at once adopted. More recently Gadow has used ‘Periarctic’ as a synonym, on the ground that it is more precise. Its faunal characteristics are those sketched in the first paragraph, with the omission of such forms as are exclusively Ethiopian (Africa, south of the Sahara) or Oriental (the Asiatic coast and islands south of the Himalayan watershed). The faunal agreement between North America and the northern part of the Old World is greater than any differences. There are few families not represented in both, and the distinctive animals are mainly local genera or species, while a great many apparently identical forms occur on both continents, having a circumpolar distribution due either to their powers of travel or to ancient land connections. Consult: Heilprin, Geographical and Geological Distribution of Animals (New York, 1887); Newton, Dictionary of Birds (New York, 1896); and the authorities referred to under Distribution of Animals. See also Nearctic Region; Palearctic Region.