If almost all dinosaurs had feathers, as recent studies have indicated, what determined which ones would evolve into birds? According to new research published in Science, the mantra of the dino-birds was “just keep shrinking.” In fact, the dinosaur lineage that produced our modern birds spent 50 million years continually getting smaller and smaller in size, while their fellow feathered dinosaurs stayed bulky. This was the key to their survival, according to researchers.
Lead study author Michael Lee, an associate professor of ecology and evolutionary biology at The University of Adelaide, said that birds are the remnants of the fastest-evolving group of dinosaurs. The family tree that his team created tracked more than 1,500 skeletal characteristics over 50 million years, showing that the theropods—the carnivorous dinosaurs, including Tyrannosaurus, that would eventually become birds—shrank markedly at least 12 times. Starting from an average mass of 163 kilograms, the theropod suborder eventually produced the .8 kilogram Archaeopteryx, which is considered the earliest bird.
The theropods, Lee said, were the only group to continually push the envelope when it came to skeletal size. It’s possible that herbivores simply couldn’t shrink, since a plant-based diet requires a larger gut for digestion. Meanwhile, theropods could explore alternate resources, habitats, and even prey. “It would have permitted them to chase insects, climb trees, leap and glide, and eventually develop powered flight,” Lee said. “All of these activities would have led to novel new anatomical adaptations.” So as the dinosaurs shrank, their other features evolved more quickly (which led to faster shrinking to take advantage of these new abilities, and so on).
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Read the full, original story: Which dinosaurs survived? The ones that shrank the fastest.
