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HYRACOIDEA
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HYRACOIDEA , a suborder of ungulate mammals represented at the See also:present See also:day only by the Syrian hyrax (Procavia syriaca), the " coney " of the See also:Bible, and its numerous See also:African relatives, all of which may be included in the single genus Procavia (or Hyrax), and consequently in the See also:family Procaviidae. These creatures have no proper See also:English name, and are generally known as hyraxes, from the scientific See also:term (Hyrax) by which they were for many years designated—a term which has unfortunately had to give See also:place to the earlier Procavia. In See also:size these animals may be compared roughly to rabbits and See also:hares; and they have rodent-like habits, hunching up their backs after the See also:fashion of some See also:foreign members of the See also:hare-family, more especially the Liu-Kiu See also:rabbit. In the See also:matter of nomenclature these animals have been singularly unfortunate. In the See also:title " hyrax " they have, for instance, usurped the See also:Greek name for the See also:shrew-See also:mouse; while in the Bible they have been given the old English name for the rabbit. Perhaps See also:rock-rabbit would be the best name. At the Cape they are known to the Dutch as class (See also:badger), which has been anglicized into " dassie." As regards the See also:recent forms, the dentition in the fully adult See also:animal consists only of incisors and cheek-See also:teeth, the See also:formula being i. c. p. #, m. if. There is, however, a See also:minute upper canine See also:developed at first, which is See also:early See also:shed; and in See also:extinct forms this tooth was Fie. i.—The Cape Hyrax (Procavia capensis). functional and molar-like. The tipper incisors have persistent pulps, and are curved longitudinally, forming a semicircle as in rodents; they are, however, not flattened from before backwards as in that See also:order, but prismatic, with an antero-See also:external, an anterointernal and a posterior See also:surface, the first two only being covered with See also:enamel; their tips are consequently not See also:chisel-shaped, but See also:sharp-pointed. They are preceded by functional, rooted See also:milk-teeth. The See also:lower incisors have See also:long tapering roots, but not of persistent growth ; and are straight, directed somewhat forwards, with See also:awl-shaped, tri-lobed crowns. Behind the incisors is a considerable See also:gap, followed by the cheek-teeth, which are all contiguous, and formed almost exactly on the See also:pattern of some of the perissodactyle ungulates. The milk-dentition includes three pairs of incisors and one of canines in each See also:jaw. The hyoid See also:arch is unlike that of any known mammai. The dorsal and lumbar vertebrae are very numerous, 28 to 30, of which 21 or 22 See also:bear ribs. The tail is extremely See also:short. There are no clavicles. In the fore See also:foot, the three See also:middle toes are subequally developed, the fifth is present, but smaller, and the first is rudimentary, although, in one See also:species at least, all its normal bones are present. The terminal phalanges of the four See also:outer digits are small, somewhat conical and flattened in See also:form. The carpus has a distinct os centrale. There is a slight See also:ridge on the femur in the place of a third trochanter. The fibula is See also:complete, thickest at its upper end, where it generally unites with the See also:tibia. The See also:articulation between the tibia and astragalus is more complex than in other mammals, the end of the malleolus entering into it. The See also:hind-foot is very like that of a See also:rhinoceros, having three well-developed toes. There is no trace of a first toe, and the fifth See also:meta-tarsal is represented by a small nodule. The terminal phalange of the inner (or second) See also:digit is deeply cleft, and has a See also:peculiar long curved claw, the others having short broad nails. The See also:stomach is formed upon much the same principle as that of the See also:horse or rhinoceros, but is more elongated transversely and divided by a constriction into two cavities—a large See also:left cul de See also:sac, lined by a very dense See also: 2.—See also:Skull and Dentition of See also:Tree-Hyrax(Procavia dorsalis) See also:female has six teats, of which four are inguinal and two axillary, and the See also:placenta is zonary and See also:deciduous. There is a gland on the back. The more typical members of the genus are terrestrial in their habits, and their cheek-teeth have nearly the same pattern as in rhinoceroses; while the See also:interval between the upper incisors is less than the width of the teeth ; and the lower incisors are only slightly notched at the cutting edge. Vertebrae: C. 7, D. 22, L. 8, S. 6, C. 6. Of this form the earliest known species, P. capensis, is the type; but there are many other species, as P. syriaca, and P. brucei from See also:Syria and eastern See also:Africa. They inhabit mountainous and rocky regions, and live on the ground. In a second See also:section the molar teeth have the same pattern as in See also:Palaeotherium (except that the third lower molar has but two lobes) ; the interval between the upper incisors exceeds the width of the teeth: and the lower incisors have distinctly trilobed crowns. Vertebrae: C. 7, D. 21, L. 7, S. 5, 1 C. lo. The members of this section frequent the trunks and large branches of trees, sleeping in holes. There are several species from Western and See also:South Africa, as P. arboreus and P. dorsalis. The members of both See also:groups appear to have a See also:power like that possessed by geckos of clinging to See also:vertical surfaces of rocks and trees by the soles of their feet. Extinct Hyracoids.—For many years extinct representative! of the Hyracoidea were unknown, partly owing to the fact that certain fossils were not recognized as really belonging to that See also:group. The longest known of these was originally named Leptodon graecus, but, on See also:account of the preoccupation of the generic title, the designation has been changed to Pliohyrax graecus. This animal, whose remains occur in the Lower See also:Pliocene of both See also:Attica and See also:Samos, wa! about the size of a donkey, and possessed three pairs of upper incisor teeth, of which the innermost were large and trihedral, recalling those of the existing genus. On the other See also:hand, the two outer pairs of incisors were in contact with one another and with the canines, so as to form on each See also:side a See also:series continuous with the cheek-teeth. The next representatives of the group occur in the Upper See also:Eocene beds of the See also:Fayum See also:district of See also:Egypt, where the genera Saghatherium and Megalohyrax occur. These are regarded as representing a distinct family, the Saghatheriidae, characterized by the See also:possession of the full series of twenty-two teeth in the upper jaw, among which the first pair of incisors was modified to form trihedral rootless tusks, while the two remaining pairs were separated from one another and from the teeth in front by gaps. The canine was like a premolar, and in contact with the first tooth of that series; and the cheek-teeth were short-crowned, with the premolar simpler than the molars. and a third See also:lobe to the last lower tooth of the latter series. The members of this genus were small or See also:medium-sized ungulates with single-rooted incisors. On the other hand, the representatives of the contemporary genus Megalohyrax were approximately as large as Pliohyrax, and in some instances had See also:double roots to the second and third incisors. It is now possible to define the suborder Hyracoidea as including ungulates with a centrale in the carpus, plantigrade feet, in which the first and fifth toes are reduced in greater or less degree, and clavicles and a foramen in the lower end of the humerus are absent. The femur has a small third trochanter, the See also:radius and ulna and tibia and fibula are respectively See also:separate, at least in the See also:young, and the fibula articulates with the astragalus. The earlier forms had the full series of 44 teeth, with the premolars simpler than the molars; but in the later types the canines and some of the incisors disappear, and at least the hinder premolars become molar-like. In all cases the first upper incisors are large and rootless. That the group originated in Africa there can be no reasonable doubt; and it is remarkable that so early as the Upper Eocene the types in existence differed comparatively little in structure from the See also:modern forms. In fact the hyraxes were then almost as distinct from other mammals as they are at the present day. See also C. W. See also:Andrews, Descriptive See also:Catalogue of the See also:Tertiary Vertebrala of the Fayum, See also:British Museum (1906). (R. Additional information and CommentsThere are no comments yet for this article.
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