Beijing, Feb 17 (Xinhua) Scientists have moved a step closer to decipher the development biology of the oldest animals on earth after researching on 600 million years old fossilised embryos found in Southwest China`s Guizhou province.

The study by US and Chinese scientists has revealed how the ancient animal embryos developed into mature adult forms, the scientists said in the latest issue of Geology, the journal of the Geological Society of America.

The scientists studied on some 80 pieces of fossilised embryos, which were formed almost 600 million years ago and showed the embryos in the act of cleaving, Yuan Xunlai, a member of the Sino-US embryos research team that carried out the study, said.

Yuan, from Chinese Academy of Sciences, said that each embryo is about the size of a grain of sand, and is composed of two to nearly 1,000 cells.

The embryos cloaked themselves inside an envelope with tiny holes in a pattern similar to stitches on a baseball that they use to transport, store or metabolise molecules, he said.

Scientists used X-ray computed tomography and other scanning equipments to peel off the envelope and discovered that the embryo cells are dividing and unfurling.

“Previously we discovered that some cells were clustered together, but they showed no signs of dividing,” he said.