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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. See also:

Huxley in his Introduction to the See also:Classification of Animals (1869), to designate a See also:province of the See also:Vertebrata formed by the See also:union of the Aves with the Reptilia. In his Elements of See also:Comparative See also:Anatomy (1864) he had used the See also:term " Sauroids" for the same province. The five divisions of the Vertebrata—See also:Pisces, See also:Amphibia, Reptilia, Aves, and See also:Mammalia—are all distinctly definable, but their relations to one another differ considerably in degree. Whilst it See also:attempt himself in 1785, by the See also:Aiguille du Goiter route. Two See also:Chamonix men attained the See also:summit in 1786, by way of the Grands Mulets, and in 1787 See also:Saussure himself had the delight of gaining the summit (the third ascent). In 1788 he spent 17 days in making observations on the See also:crest of the See also:Col du See also:Grant (11,o6o ft.). In 1774 he mounted the Crammont, and again in 1778, in which See also:year he also explored the Valsorey See also:glacier, near the See also:Great St See also:Bernard. In 1776 he had ascended the Buet (10,201 ft.). In 1789 he visited the See also:Pizzo Bianco (near See also:Macugnaga) and made the first traveller's passage of the St Theodule Pass (1o,8gq ft.) to See also:Zermatt, which he was the first traveller to visit.

On that occasion he climbed from the pass up the See also:

Klein See also: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 See also:Roche See also: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 See also:quarto volumes, under the See also:general See also:title of Voyages clans See also:les Alpes (1779–1796; there was an See also:octavo issue in eight volumes, issued 178o-1796, while the non-scientific portions of the See also:work were first published in 1834, and often since, under the title of Partie pittoresque See also:des ouvrages de M. de Saussure). was Huxley's great merit to emphasize by the term Sauropsida the See also:close and See also:direct relationship between the classes of See also:reptiles and birds, it was an unfortunate innovation to See also: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 See also:recent Vertebrata lies between fishes, absolutely aquatic creatures with See also:internal gills and " fins " on the one See also:side, and on the other side all the other, tetrapodous creatures with lungs and fingers and toes, for which H. See also:Credner has found the excellent term of Tetrapoda. Another See also:drawback of Huxley's divisions resulted in the tendency of alienating the Mammalia, the third See also:division, from the reptiles whilst trying to connect their ancestry with the Amphibia, a view which even now has some vigorous See also:advocates. The characters which distinguish the Sauropsida, that is, which are See also:common to birds and reptiles, and not found combined in the other classes, have been thus summarized by Huxley: no branchiae at any See also:period of existence; a well-See also:developed amnion and allantois See also:present in the embryo; a mandible composed of many bones and articulated to the See also:skull by a quadrate See also:bone; nucleated See also:blood-corpuscles; no See also:separate paraspheroid bone in the skull; and a single occipital condyle. In addition to these See also: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 See also:body cavity. The adult See also:kidney is a metanephros with separate ureter; the mesonephros and mesonephric duct become in the adult male the efferent duct of the testis. The See also:intestine and the reproductive and urinary ducts open into a common See also:cloaca.

There is usually an exoskeleton in the See also:

form of scales; in the birds the scales take the form of feathers. There are two aortic See also:arches in reptiles, in birds only one—the right. The See also:heart is usually trilocular, becoming quadrilocular in crocodiles and birds. In all the eggs are mero- See also:primitive, and the question, what See also:group of reptiles has given rise to the birds? is still unanswered. By See also:irony of See also:fate, See also:mere lack of the fossil material, it has come to pass that the See also: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.

End of Article: SAUROPSIDA

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SAUSSURE, HORACE BENEDICT DE (1740-1799)

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