MEG'ATHE'RIUM (Neo-Lat., from (1k. cayos, mcgos. great + Onplov, thfrion, diminu tire of Hp, thCr, wild beast). A gigantic fossil edentate mammal, larger than a rhinoceros, which lived in comparatively recent geological time in South America, and of which skeletons are found in the pampenn deposits Pleistocene) of Argentina, Chile, and Brazil. Its skeleton, which shows points of resemblance to both the anteaters and sloths, is of very massive con struction, indicating a most powerful animal, about 18 feet in length. The bead was small, the jaws of a. form to support powerful chewing muscles. and the teeth, of which there are only ten upper and eight lower molars, are of a pris matic form and of size as must have rendered them most. effective grinding organs. The structure of the forward portion of the jaws FlIOW,4 the lips to have been elongated and prehensile, and the grooved inside of the lower jaw suggests a powerful prehensile tongue, which served to pull off the twigs and leaves upon which the animal fed. The neck was short and strong. the trunk heavy and round. The leg bones are extraordinarily massive and of peculiar form. The fore limbs are longer than the hind limbs. and the form of their joints indicates ennsiderabie flexibility: they probable served somewhat as arms. The very heavy hind-limb hones and the tail bones indiente that the greater portion of the weight of the animal was borne by these parts, and it is reasonable to conclude that the favorite position of the beast ca ,s that of resting upon its haunches. The surfaces of the hones are provided with ridges and rough places for the attachment of inmerfni muscles.
The size of the animal, its evidently very great muscular power. and the structure of its hind quarters. indicate that it squatted beside a tree and with its nuthile fore limbs, the middle lingers of which were armed wi1Ir -1. Claws, 111111A down and broke off the upper trunk and branches from which it derived its food. The body of the animal is thought to have been covered by hide and coarse hair. Mcgatherium was one of the first fossil mammals described. A nearly complete skeleton was found in 1739 near Buenos Ayres and sent to the museum of Madrid, where it was described and named by Caviler, clegat he rinm Am erican us.
Three other allied genera are Seelidotherium, Slegalonyx, and Slylodon. all of Pleistocene age. Of these, Seelidotherium. from South America, in the structure of its skull, resembles closely a gigantic anteater. Megalonyx, differing slightly front Alegatherium in the structure of its teeth, has been found in the cave deposits of Ken tucky and Tennessee and in the Pleistocene beds of Cuba. The remaining form, Mylodon, re mains of which have been found in Kentucky and South America, is the only member of the family Alegatherifibe in which the skin contains calcareous plates similar to those of the other group of gigantic edentates:. the Glyptodontidx: and in Slylodon these plates. though numerous, are small and not joined to each other. Consult Woodward, Outlines of Vertebrate Paleontology (Cambridge, 1898).