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RE: Thalassocnus...the naked sloth?
Brian Lauret wrote:
I'm allmost sure most people on this list have heard about the Thalassocnus
species series. These nothrotheriid xenarthrans evolved from terrestrial
herbivores into (semi-)marine seacow-
lookalikes,complete with the broad snouts.
Now I wonder, would this convergence have gone as far as these fascinating
critters being hairless like a seacow? I wonder especially about the later
species as I'm quite sure the most basal ones were still hairy.
_Thalassocnus_ may have been either hairy or naked. Although many mammals
that spend most or all of the time in the water are nearly hairless (e.g.,
sirenians, whales, hippos), others retain a pelt (e.g., pinnipeds, otters,
beaver). The authors who described _Thalassocnus_ (de Muizon and McDonald,
1995) note that the tail is similar to that of otters and beavers (see
I do not know wether I find the idea of a naked ground sloth very pleasant
Well, technically _Thalassocnus_ isn't a "ground sloth" any more, but a
"water sloth". :-)
de Muizon, C., and H. G. McDonald. (1995). An aquatic sloth from the
Pliocene of Peru. Nature (London) 375: 224-227.
Abstract: Ground sloths (Gravigrada, Xenarthra) are known from middle or
late Oligocene to late Pleistocene in South America1 and from late Miocene
to late Pleistocene in North America. They are medium to gigantic in size
and have terrestrial habits. Discovery of abundant and well preserved
remains of a new sloth (_Thalassocnus natans_), in marine Pliocene deposits
from Peru drastically expands our knowledge of the range of adaptation of
the order. The abundance of individuals, the absence of other land mammals
in the rich marine vertebrate fauna of the site, and the fact that the
Peruvian coast was a desert during the Pliocene suggest that it was living
on the shore and entered the water probably to feed upon sea-grasses or
seaweeds. The morphology of premaxillae, femur, caudal vertebrae (similar
to those of otters and beavers) and limb proportions are in agreement with