"The world's first monkeys to be created from the embryos of several individuals have been born at a US research centre. Scientists at the Oregon National Primate Research Centre produced the animals, known as chimeras, by sticking together between three and six rhesus monkey embryos in the early stages of their development....The first chimeric animals were created by researchers in the 1960s, when experiments with mouse embryos showed they could combine to form a single mouse of normal size. Since then, scientists have created chimeric versions of rats, rabbits, sheep and cattle."
More http://www.guardian.co.uk/science/2012/jan/05/chimera-monkeys-combining-several-embryos