This Massive Tunnel in South America Was Dug by Ancient Mega-Sloths

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In the last ten years, more than 1,500 large burrows have been discovered in southern and southeastern Brazil, dug in rocks that include weathered granitic and basaltic rocks, sandstones, and other consolidated sediments.

image credit: Heinrich Frank

Their presence in geological units of Plio-Pleistocene age suggests that large extinct mammals produced these structures. The internal walls exhibit scratches and grooves left by the animals that inhabited these structures.

image credit: Heinrich Frank

The burrows are straight or slightly sinuous tunnels that measure up to tens of meters in length. One smaller type measures up to 1.5 meter in diameter, and the larger type can reach 2 meters in height and 4 meters in width.

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These megatunnels are probably the handiwork of giant ground sloths—humongous “paleoburrows” that no longer walk the Earth.

image credit: Heinrich Frank

Suggesting that such structures have been produced by at least two kinds of organisms. This contribution proposes a classification for these ichnofossils under the generic designation Megaichnus consisting of two ichnospecies identified so far.

image credit: Wikimedia Commons

Although the exact identity of the producers of the burrows is yet unknown, the dimensions and morphology point to ground sloths and giant armadillos.