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Dinosaurs Live On as "Most Successful Land Species"

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Today’s birds are basically baby dinosaurs

It may be hard to imagine that your common house sparrow is the direct descendant of the dinosaurs (to be precise, she is a dinosaur). But we know it’s true. And now we know a little more about how the transition took place.

A group of Harvard scientists have shown how today’s birds have much in common with baby theropods (the group that includes velociraptors). As the dinos grew and matured, their skulls changed shape. But today’s birds retain the shape of their forebears as babies, and it seems that what some of those babies did was to speed up the clock of their development and retain the baby skull shape while reaching maturity much quicker.

“We examined skulls from the entire lineage that gave rise to modern birds,” said Arkhat Abzhanov, Associate Professor of Organismic and Evolutionary Biology. “We looked back approximately 250 million years, to the Archosaurs, the group which gave rise to crocodiles and alligators as well as modern birds … to try to understand what actually happened during the evolution of the bird skull.”

The team found that while early dinosaurs underwent major morphological changes as they matured, the skulls of juvenile and adult birds remain remarkably similar.

“In the case of birds, we can see that the adults of a species look increasingly like the juveniles of their ancestors,” Abzhanov said.

In the case of modern birds, he said, the change is the result of a process known as progenesis, which causes an animal to reach sexual maturity earlier. Unlike their dinosaurian ancestors, modern birds take dramatically less time – just 12 weeks in some species – to reach maturity, allowing birds to retain the characteristics of their juvenile ancestors into adulthood.

The study is published in the journal Nature.