Science Focus
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We tend to think of feathers as one of the defining features of birds. But in recent years, it's become apparent that the lineage of dinosaurs that gave rise to birds (the Theropods) had feathers millions of years before anything remotely bird-like existed. Just last week, feathers were also found on a dinosaur outside the theropod lineage, raising questions about what made the theropods special (aside from, well, all sorts of cool dinosaur species).
Previous attempts to detect any global trends in bird-like traits among the theropods haven't come up with anything definitive. But today, scientists are releasing a new computer analysis of thousands of traits from theropod dinosaur fossils. The results show that the lineage that gave rise to birds has been getting smaller for 50 million years, and it underwent a huge burst of adding novel anatomical features. Both of these revelations are in sharp contrast to the rest of the theropod lineage.
The first theropods appear in the fossil record after the Triassic-Jurassic mass extinction event. During the early part of their history, they were notable for being rather large and static. Some groups appeared in the fossil record 180 million years ago, persisting right up to the mass extinction event that ended the non-avian dinosaurs. And one of the earliest groups to split off the lineage that led to birds were the Megalosaurids—which, as their name implies, were rather large.
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