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UNGULATA

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Originally appearing in Volume V27, Page 581 of the 1911 Encyclopedia Britannica.
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UNGULATA , the name of an See also:

order of placental mammals in which the terminal See also:joints of the toes are usually encased in solid hoofs or covered with broad hoof-like nails, while the molar (and not unfrequently some or all of the premolar) See also:teeth have broad tuberculated crowns adapted for crushing See also:vegetable substances. The teeth (when all are See also:present) are differentiated into the usual four See also:series; and See also:milk-teeth, not completely discarded till the full stature is attained, are in-variably See also:developed. All the existing members of the See also:group are eminently adapted for a terrestrial See also:life, and in the See also:main for a vegetable See also:diet. Though a few may in some circumstances kill living creatures smaller than themselves for See also:food, none are habitually predaceous. In none of the existing, and in but few of the See also:extinct types, are See also:collar-bones, or clavicles, developed; and the scaphoid and lunar bones of the carpus are See also:separate. The typical ungulates are the members of the suborders See also:ARTIODACTYLA and See also:PERISSODACTYLA (q.v.), in both of which the bones of the See also:foot articulate with each other by means of groove-and-See also:tongue joints, whence the name of Diplarthra (See also:equivalent to Ungulata See also:Vera), which has been See also:pro-posed for these two See also:groups collectively, as distinct from the other representatives of the order. The remaining and less typical subordinal groups—sometimes ranked as orders by themselves—include among living animals the See also:Proboscidea, or elephants, and the See also:Hyracoidea, or hyraxes, and among extinct groups the See also:Amblypoda, See also:Ancylopoda, Barypoda, Condylarthra, See also:Litopterna and See also:Toxodontia. The characteristics of these groups will be found under their respective headings, with the exception of the Barypoda and Condylarthra, for which see See also:ARSINOITHERIUM and See also:PHENACODUS. In the See also:great See also:majority of the Subungulata the bones of the upper and See also:lower rows ofthe See also:wrist-See also:joint, or carpus, retain the See also:primitive or more typical relation to each other (see fig., and contrast with PERISSODACTYLA, fig. I); the os magnum of the second See also:row articulating mainly with the lunar of the first, or with the See also:cuneiform, but not with the scaphoid. On the other See also:hand in the Diplarthra, the group to which the vast majority of See also:modern Ungulates tg belong, the second or lower row has been shifted altogether towards the inner See also:side of the See also:limb, so that the magnum is brought considerably into relation with the scaphoid, and is entirely removed from the cuneiform, as in most existing mammals. In the typical Ungulata or Diplarthra, the feet are never plantigrade, and the functional toes do not exceed four—the inner See also:digit being suppressed, at all events in all forms which have existed since the See also:Early See also:Eocene See also:period.

The os magnum of the carpus articulates freely with the scaphoid. The See also:

allan- tois is largely developed, and the See also:placenta, so far as known, is nondeciduate, the chorionic villi being either evenly diffused or collected in groups or cotyledons (in See also:Pecora). The testes descend into a scrotum. There is never an os penis. The uterus is bicornuate. The teats are usually few, and inguinal, but may be numerous and abdominal (as in See also:Suina), although they are never solely See also:pectoral. The cerebral hemispheres in existing Ungulates are well convoluted. (R.

End of Article: UNGULATA

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