Reptilia
reptiles; cold-blooded, oviparous, or ovoviviparous, vertebrate animals having the skin covered with scales or scutes; heart with two auricles, ventricular chamber incompletely divided. Respiration takes place by lungs, respiratory movements being slow and irregular. Intestinal tract and urogenital organs open into a common cloaca. Aristotle was the first naturalist who wrote on reptiles. Some progress in classification was made by Ray (1628- 1705) and Linnæus (1707-1778).
Brongniart, in 1799, first recognized the characteristics by which the Batrachia differ from other reptiles and form a natural passage to the fishes. In 1863 in his Hunterian Lectures, Huxley adopted the term Sauroids for that division of the vertebrates which he afterward called Sauropsida. He divides the Reptilia into the following orders: Chelonia, Plesiosauria, Lacertilia, Ophidia, Ichthyosauria, Crocodilia, Dicynodontia, Ornithoscelida, and Pterosauria. Owen makes reptiles proper the highest of the five sub-classes into which he finally divided his Hæmatocrya with orders: Ichthyopterygia (extinct), Sauropterygia (extinct), Anomodontia (extinct), Chelonia, Lacertilia (with the extinct Mosasaurus), Ophidia, Crocolilia (with the extinct Teleosaurus and Strepsospondylus), Dinosauria (extinct), and Pterosauria (extinct).
Professor Mivart divides the Reptilia into the following orders:
Ichthyopterygia (extinct), Anomodontia (extinct), Dinosauria (extinct), Ornithosauria (extinct), Crocodilia, Rhynchocephalia, Sauropterygia, Lacertilia, Ophidia, and Chelonia. The first appearance of reptiles is believed to be indicated by remains of a marine Saurian (Eosaurus acadianus) of Carboniferous age. Proterosaurus is found in the Permian. In Mesozoic times the reptilian type appears in such variety and in such a high state of development that this era has been distinguished as the Reptilian Age. In the Trias large marine Saurians and Dinosaurs are met with; more gigantic forms were developed in the Jurassic period; and the class attained its highest culmination in the Chalk.