THE oldest embryos ever discovered reveal that some early dinosaurs crawled on all fours before learning to stand upright.
A team from the US, Canada and South Africa used the latest archaeological tools 鈥� including miniature jackhammers and fine dental drills 鈥� to crack open two of six 190 million-year-old dinosaur eggs discovered in the Golden Gate Highlands National Park, South Africa, in 1978, which were too fragile to examine at the time.
Inside they found a pair of perfectly formed baby Massospondylus carinatus, a long-necked herbivore that stalked on two large hind legs during the late Triassic and early Jurassic period, 220 to 183 million years ago.
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The shape and size of each embryo鈥檚 head, neck and forearms suggests that baby Massospondylus crawled on four limbs after hatching, learning to walk on two legs only later on in life (Science, vol 309, p 761). The researchers suspect the hatchlings鈥� large heads may have been too heavy for their long, horizontally oriented necks to support them comfortably.
鈥淚 can鈥檛 think of any living vertebrate that does this,鈥� says Robert Reisz of the University of Toronto, Canada, who led the research, 鈥渆xcept possibly us, and we are terribly awkward as hatchlings.鈥�
