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SAUROPSIDA

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Originally appearing in Volume V24, Page 238 of the 1911 Encyclopedia Britannica.
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SAUROPSIDA. This name was introduced by T. H. Huxley in his Introduction to the Classification of Animals (1869), to designate a province of the Vertebrata formed by the union of the Aves with the Reptilia. In his Elements of Comparative Anatomy (1864) he had used the term " Sauroids" for the same province. The five divisions of the Vertebrata—Pisces, Amphibia, Reptilia, Aves, and Mammalia—are all distinctly definable, but their relations to one another differ considerably in degree. Whilst it attempt himself in 1785, by the Aiguille du Goiter route. Two Chamonix men attained the summit in 1786, by way of the Grands Mulets, and in 1787 Saussure himself had the delight of gaining the summit (the third ascent). In 1788 he spent 17 days in making observations on the crest of the Col du Grant (11,o6o ft.). In 1774 he mounted the Crammont, and again in 1778, in which year he also explored the Valsorey glacier, near the Great St Bernard. In 1776 he had ascended the Buet (10,201 ft.). In 1789 he visited the Pizzo Bianco (near Macugnaga) and made the first traveller's passage of the St Theodule Pass (1o,8gq ft.) to Zermatt, which he was the first traveller to visit. On that occasion he climbed from the pass up the Klein Matterhorn (12,750 ft.), while in 1792 he spent three days on the same pass (not descending to Zermatt), making observations, and then visited the Theodulhorn (11,392 ft.). In 1780 he climbed the Roche Michel, above the Mont Cenis Pass. The descriptions of seven of his Alpine journeys (by no means all), with his scientific observations gathered en route, were published by him in four quarto volumes, under the general title of Voyages clans les Alpes (1779–1796; there was an octavo issue in eight volumes, issued 178o-1796, while the non-scientific portions of the work were first published in 1834, and often since, under the title of Partie pittoresque des ouvrages de M. de Saussure). was Huxley's great merit to emphasize by the term Sauropsida the close and direct relationship between the classes of reptiles and birds, it was an unfortunate innovation to brigade the Amphibia and fishes as Ichthyopsida, thereby separating the Amphibia much more from the reptiles than is justifiable, more than perhaps he himself intended. The great gulf within the recent Vertebrata lies between fishes, absolutely aquatic creatures with internal gills and " fins " on the one side, and on the other side all the other, tetrapodous creatures with lungs and fingers and toes, for which H. Credner has found the excellent term of Tetrapoda. Another drawback of Huxley's divisions resulted in the tendency of alienating the Mammalia, the third division, from the reptiles whilst trying to connect their ancestry with the Amphibia, a view which even now has some vigorous advocates. The characters which distinguish the Sauropsida, that is, which are common to birds and reptiles, and not found combined in the other classes, have been thus summarized by Huxley: no branchiae at any period of existence; a well-developed amnion and allantois present in the embryo; a mandible composed of many bones and articulated to the skull by a quadrate bone; nucleated blood-corpuscles; no separate paraspheroid bone in the skull; and a single occipital condyle. In addition to these principal characters others exist which are found in all birds and reptiles, but are not exclusively confined to them. The oviduct is always a Mullerian duct separate from the ovary and opening from the body cavity. The adult kidney is a metanephros with separate ureter; the mesonephros and mesonephric duct become in the adult male the efferent duct of the testis. The intestine and the reproductive and urinary ducts open into a common cloaca. There is usually an exoskeleton in the form of scales; in the birds the scales take the form of feathers. There are two aortic arches in reptiles, in birds only one—the right. The heart is usually trilocular, becoming quadrilocular in crocodiles and birds. In all the eggs are mero- primitive, and the question, what group of reptiles has given rise to the birds? is still unanswered. By irony of fate, mere lack of the fossil material, it has come to pass that the bridges between Amphibia and reptiles and from them to Mammals are in a fairer way of re-construction than is that between reptiles and birds, the very two classes of which we know that they " belong together." (H. F. G.)
End of Article: SAUROPSIDA
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