Online Encyclopedia

NORTH AMERICA

Online Encyclopedia
Originally appearing in Volume V23, Page 175 of the 1911 Encyclopedia Britannica.
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NORTH AMERICA.—Of this huge continent only the United States and Mexico come into consideration, since N. of 45 ° latitude reptilian life is very scarce. The area, however, with these restrictions, is larger than the Indian and Malay countries, and larger than the Australian region. Yet the fauna is comparatively poor, very poor indeed, if it were not for Mexico and the Sonoran province, which seems to be the ancient centre of distribution of much of the present typically N. American fauna. Characteristic of the area is the abundance of Chelonians and Iguanidae, to which Tejidae have to be added in the S.; equally characteristic is the complete absence of Pleurodirous Chelonians, of Chameleons, Agamidae, Lacertidae, Varanidae and Viperinae. The fauna is composed as follows: Crocodilia, with Crocodilus americanus and Alligator mississippiensis in the S. Of Chelonians the Chelydridae, peculiar to the E. half but for the reappearance of a species of Chelydra in Central America; many Cinosternidae like-wise almost peculiar to the area; of Testudinidae an abundance of freshwater forms, notably Chrysemys,'and Emys in common with Europe, whilst terrestrial tortoises are extremely scanty, namely one species of Testudo, T. Polyphemus, the gopher, and two of Cistudo, e.g. C. carolina; lastly, two Trionyx in the whole of the Mississippi basin and thence N. into Lake Winnipeg, 51° N. Lacertilia: Geckos are very scarce; N. America has received only Sphaerodactylus notatus from the Antilles into Florida, and Phyllodactylus tuberculosus into California from the Pacific side of Mexico; Eublepharinae are absent. Of Iguanidae we have a typically Sonoran set, e.g. Crotaphytus, Holbrookia, Uta, Phrynosoma, Sceloporus, and a S. set of which only Anolis extends out of the tropics. It is significant that only a few species of Sceloporus and Phrynosoma extend into the United States, although far N.; of the large genus Anolis only A. carolinensis enters Texas to Carolina. Sceloporus may be called the most characteristic genus of Sonoraland and Mexico. Of the tropical family of Tejidae only Cnemidophorus, with many species in Mexico, a few in the adjoining N. states, and with C. sexlineatus over the greater part of the Union. Angusdae: Ophisaurus ventralis in the United States; the other species in the Old World. Diploglossus peculiar to mountains of Mexico. Gerrhonotus, the main genus, centred in Mexico, but G. coeruleus ranges from Costa Rica along the Pacific side right into British Columbia, the most northern instance of a New World reptile. Xenosaurus grandis of Mexican mountains is the monotype of a family, and the same would apply to Heloderma (H. suspectum, the Gila monster of the hottest lowland parts of Arizona and New Mexico; and H. horridum of Mexico) if it were not for Lanthanotus of Borneo. Scincidae: of this cosmopolitan family America possesses the smallest number, and it is significant that the number of species decreases from N. to S.; Eumeces from Minnesota and Massachusetts through Mexico, with many species, and Lygosoma s. Mocoa laterale from S.E. and Central States to Mexico. Xantusiidae, a small family,. is composed of a N. or Sonoran and a S. or Central American-Antillean group; e.g. Xantusia of the deserts of Nevada and California. Amelia, monotype of a family of California to El Paso, Texas, i.e. peculiar to Sonoraland, Amphisbaenidae with Rhineura in Florida and the marvellous Chirotes in Lower California and the Pacific side of Mexico; the other members of this family are tropical so far as America is concerned. Snakes: of Typhlopidae only Anomalepis mexicana, peculiar to Nuevo Leon; of Glauconiidae several extending N. into Texas and Florida. Boinae continue N. as the arenicolous Lichanura of Lower California and Arizona, and the likewise arenicolous Charina bottae which extends from California to the state of Washington; the other members of the family are all tropical, extra-regional. Of Viperidae only pit vipers occur, but of them rattlesnakes cover the whole of the habitable area; Ancistrodon, without a rattle, e.g. the moccasin snake and the water viper, has other species in central and E. Asia. Of Elapinae, far into the E. United States only the genus Elaps with a few species, of which E. fulvius, the commonest, ranges from S. Brazil far into the S.'and E. states. A few opisthoglyphous, terrestrial, snakes just enter the United States from Mexico, e.g. Trimorphodon. Of aglyphous colubrines species of genera like or resembling Tropidonotus, Coronella and Coluber, including Pityophis and Spilotes, are abundant, the latter being very characteristic; Ischnognathus and Conga, Ficimia and Zamenis likewise are clearly nearctic, or Sonoran. The Greater Antilles have essentially neotropical, i.e. Central American and S. American affinities, but there is also some Sonoran infusion.—There is Crocodilus americanus; no Chelonians are natives except one or two Chrysemys. Of Lacertilia, geckos are abundant; of Iguanidae several arboreal forms, notably the large Iguana, and Metopoceras of Haiti, and Cyclura, both peculiar; of Anguidae Celestus, peculiar, but closely allied to Diploglossus; of Xantusiidae the peculiar genus Cricosaura s. Cricolepis. Of Amphisbaenidae Amphisbaena itself occurs in Puerto Rico and on the Virgin Islands. Of Tejidae only Ameiva, not Cnemidophorus. Snakes: a Typhlops in Puerto Rico; of boas Epicrates, Ungalia and Corallus, the latter re-occurring in Madagascar. Absent are: Viperidae, Elapinae and Opisthoglyphs; of aglyphous colubrines the Central American genera Urotheca, Dromicus, Drymobius and Leptophis; the genera of distinctly northern origin.
End of Article: NORTH AMERICA
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