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Homalodotherium cunninghami Click here to see the skeleton The Santa Cruz formation is the best known and most thoroughly studied of all South American tertiary stages. Because of South Americas isolation from North America during the Miocene, the terrestrial fauna is quite different and unique in comparison. One of the largest of the Santa Cruz land mammals, though not huge in comparison with some North American giants, was the Toxodont, Homalodotherium. An exceptionally strange creature in its proportions, it's lifestyle has been the the subject of much speculation. The rear limbs are short and the feet are plantigrade while the forelimbs are long and powerful and the toes semi-digitigrade and terminate in large deeply cleft claws. The massive humerous ( upper arm bone ) has prominent ridges for the attachment of the deltoid and supinator muscles suggesting an enhanced ability to dig or pull .The articulations of the wrist show a considerable range of flexibility and the phalanges could grasp quite well. The hind feet show that Homalodotherium walked on the outside edge of the foot, pigeon-toed fashion much like the giant ground sloths. The skull is short and deep with abbreviated nasal bones suggesting the possibility of a trunk or inflatable muzzle. Much like the Ancylopod Chalicotheres of north America and Eurasia, it is believed that Homalodotherium was a browser, using its long clawed arms to pull down tree branches to feed on leaves, and possibly a digger, rooting out fallen fruits, seeds and tubers.
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