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The two main branches of placental mammals split while dinosaurs still roamed
the Earth, according to a new study of 85 million-year-old fossils from
Uzbekistan (Nature, vol 414, p 62). The findings push back the date for
fossil evidence of the split by 20 million years, says David Archibald of San
Diego University, California. 鈥淵ou can recognise one group that evolved into
rabbits and rodents,鈥� says Archibald, and another that evolved into
ungulates鈥攈oofed mammals such as horses and goats.