March 13, 2014
Ancient Sloths Went Out Of The Trees And Into The Water
Lee Rannals for redOrbit.com - Your Universe Online
Scientists at the National Museum of Natural History in Paris say ancient sloths once spent some of their time in the ocean.
Sloths are known as tree dwellers, but the latest research published in the Proceedings of the Royal Society B says that these creatures use to head out into the sea about five to eight million years ago.
The team came to this conclusion after analyzing Peruvian sloth fossils belonging to five different species of Thalassocnus. They determined that these ancient creatures had clear signs of a bony adaption that would be found in animals returning to the sea. Modern-day sloths have dense bones, which would make them less buoyant than their aquatic relatives which were able to head down to the seafloor for food.
Researchers performed CT-scans on thin slices of bone to measure out the bone compactness, which reveals bone density. They measured ribs, femurs, tibia and other long bones taken from these fossils.
“The bones of terrestrial pilosans (sloths and anteaters) are much more compact than the mean mammalian condition, which suggests that the osteosclerosis of Thalassocnus may represent an exaptation,” the authors wrote.
The scans revealed that fossils from earlier time points were even more compact than those from later. This finding reveals the evolutionary shift and gradual acquisition from being an aquatic creature to a tree-dweller.
“It yields the most detailed data about the gradual acquisition of aquatic adaptations among tetrapods, in displaying increasing osteosclerosis and pachyostosis through time,” researchers wrote in the journal. “Such modifications, reflecting a shift in the habitat from terrestrial to aquatic, occurred over a short geological time span.”
The researchers believe that the earlier sloths use to come down to the beaches to consume sea grasses exposed to the air during low tides. These animals may have been wading in shallow water to graze on this vegetation.
“Over time, [the sloths] become better adapted to an aquatic habitat where they go out and swim, and dive down in order to feed more often and not just with the tides,” Greg McDonald, a senior curator of natural history for the U.S. National Park Service, told the National Geographic.
Sloths may have not been as aquatic when compared to creatures like seals, but the study does reveal yet another weird characteristic about the world’s slowest mammal.