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MEOATHERIUM (properly Megalotherium)
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See also:MEOATHERIUM (properly Megalotherium) , a huge See also:extinct edentate mammal from the See also:Pleistocene deposits of Buenos Aires, typifying the See also:family Megatheriidae (or Megalotheriidae), and by far the largest representative of the See also:Edentata. Except, indeed, for its relatively shorter limbs Megatherium americanum rivalled an See also:elephant in bulk, the See also:total length of the See also:skeleton being 18 feet, five of which are taken up by the tail. The Megatheriidae, which include a number of genera, are collectively In See also:form, as shown in fig. 2, the See also:teeth are quadrangular prisms, each of which is surmounted by a pair of transverse ridges. They See also:grew apparently throughout See also:life, and were implanted to a See also:great See also:depth in the jaws, being 7 or 8 in: in length, with a See also:cross-See also:section of at least an See also:inch and a See also:half. The ridges on the See also:crown are due to the arrangement of the See also:vertical layers of hard dentine (fig. 3, (I), softer vasodentine (v) and See also:cement (c). The See also:skull is relatively small, with the See also:lower See also:jaw very deep in its central portion, and produced in See also:part into a See also:long snout-like symphysis for the reception, doubtless, of a large and fleshy See also:tongue (fig. 2). Unlike sloths, the megatherium has seven cervical vertebrae; and the spines of all the See also:trunk-vertebrae incline backwards. The See also:pelvis and See also:hind-limbs are much more powerful than the fore-quarters; thereby enabling these animals, in all See also:probability, to See also:rear themselves on their hind-quarters, and thus pull down the branches of trees: if not, indeed, in some cases to bodily uproot the trees them-selves. Large See also:chevron-bones are suspended to the vertebrae of the- tail, which was massive, and probably afforded a support when the See also:monster was sitting up. The humerus has no foramen, and the
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I.—Skeleton of the Megatherium, from the specimen in the Museum of the Royal See also:College of Surgeons of See also:England.
known as ground-sloths, and occupy a position intermediate between the sloths and the See also:ant-eater: their skulls being of the type of the former, while their limbs and vertebrae conform in structure to those of the latter. As in the other typical See also:South See also:American edentates, there are no teeth in the front of the jaws, while those of the cheek-See also:series usually comprise five pairs,in the upper and four in the lower. In nearly all the other Pleistocene forms these teeth were subcylindrical in shape, with the See also:summit of the crown (except sometimes in the first pair) forming a See also:cup-like depression; See also:enamel being in all cases absent. From all these Megatherium differs in the form and structure of the teeth.
(From See also:Owen.)
whole fore-See also:limb was very See also:mobile. The first front toe was rudimentary, having no phalanges, but the fifth was rather less aborted, al-though clawless; the other three carried enormous claws, protected by reflected sheaths. The hind-See also:foot is remarkable for the great back-See also: Additional information and CommentsThere are no comments yet for this article.
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