Body trait analysis shows the miniaturisation of theropods started about 50 million years before Archaeopteryx, the earliest bird, lived.

Theropods went from 270 kilograms to less than 1 over around 50 million years



The steady downsizing and elegant evolution of the theropods is detailed in the journal Science.





Consistent shrinking


The first theropods were large, weighing around 270 kilograms (600 pounds). They roamed about 220 million to 230 million years ago. Then about 200 million years ago, when some of the creatures weighed about 160 kilograms (360 pounds), the shrinking became faster and more prolonged, the study said. In just 25 million years, the beasts were slimmed down to barely 45 kilograms (100 pounds). By 167 million years ago, 3-kilogram (6-pound) paravians, more direct ancestor of birds, were around.

And 163 million years ago the first birds, weighing less than a kilogram, probably came on the scene, the study said







The scientists detail their findings in the journal Science.