The 48-million-year-old Indohyus is a close relative of the whales. His bony structure and tooth texture indicate that he spent most of his time in the water, as in this reconstruction, diving in a river.
Read aloud Paleontologists have discovered the last four-legged ancestor of the whales: The cohort called Indohyus lived 48 million years ago and was only about the size of a fox, but resembled in the shape of today's deer. He lived differently than previously thought partly in the water, the researchers report to Hans Thewissen. Ever since Darwin, scientists have agreed that whales are descended from land mammals that went into the water. Often in this context, a carnivorous mammal was suspected, which expanded its food on marine fish. A whole series of fossils already showed the intermediate steps on the way from the land into the water, but so far the identity of the land ancestor was unknown. The scientists in India now found the 48-million-year-old evidence: The fossils of Indohyus have important key features in the skull and ear, with which the researchers could identify him as the closest relative of the whales.

A closer examination of the bone structure provided further important information. So the outermost layer of bones was heavily thickened? a phenomenon called osteosclerosis, which makes it easier to walk on the floor by adding weight. Such structures are also known in other wading animals such as today's hippo or other marine mammals. So the animal must have been partially in the water and not have had a purely terrestrial lifestyle, as previously assumed. This is also confirmed by dental analyzes of the fossil, which show similarities to partially aquatic animals.

Although the idea of ​​a miniature deer living underwater sounds bizarre, explain the researchers. But also modern cloven-hoofed animals show such a way of life: the fallow-deer living in Africa, for example, gets into the water when threatened with danger and continues on the ground under water.

Hans Thewissen (Northeastern Ohio Universities College of Medicine, Rootstown) et al .: Nature, Vol. 450, p. 1190 ddp / science.de? Christina Taraschewski ad

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