The big question, still to be answered definitively, is why later tyrannosaurids lost the fine feathers of their distant, more primitive tyrannosauroid ancestors. The team concluded that, while at least some of the early tyrannosauroids (like Yutyrannus ) were feathered, by the time tyrannosaurids had evolved more than 20 million years later, they appear to have lost all the fuzzy stuff. Writing today in Royal Society Journal Biology Letters, researchers compiled the first ever detailed analysis of tyrannosaur skin from multiple specimens, as well as a new dataset tracking tyrannosaur body size and type of skin covering from existing specimens spanning much of their evolutionary history. Consider the amount of diversity possible over tens of millions of years. There is quite a difference in furriness between us and our closest living relatives, bonobos and chimps, and we’ve only been separated from them, genetically speaking, for a few million years. Think of “-oids” as something like but not quite : humans versus humanoids in every cheesy sci-fi show ever, or hominins (us, and our immediate evolutionary kin) and hominoids, which include all the hominins plus apes, chimpanzees and orangutans. A difference of several million years of evolution, to put a finer point on it. There is a big difference between a tyrannosaur oid like Yutyrannus and a tyrannosaur id like T. Feathers are an advanced, or derived trait, and derived traits, once established, usually (but not always) stick with an evolutionary lineage. rex of the Late Cretaceous included, might also be rocking the fluffy stuff. rex with evidence of feathers, once Yut turned up in all its Early Cretaceous feathered glory, it was logical to think that later tyrannosaurs, T. So finding the great feathery beast that is Yutyrannus was a bit of shock. (Technically, Yutyrannus had a coat of primitive, filamentous feathers that would have appeared almost fur-like, rather than the advanced, much more structured feathers of modern birds.)Īlthough paleontologists have never found a T. Bigger animals generate more body heat and would be more concerned with shedding it to avoid overheating. Smaller animals don’t generate as much body heat, so they need more insulation - in this case, more feathers. The thinking was (and still is) that feathers first evolved in dinosaurs not for flight or showy peacockery displays but for insulation. Yutyrannus was a big deal because the other feathered dinosaurs in the fossil record have been significantly smaller. Artist’s 2012 rendering of a pack of Yutyrannus surrounded by smaller but equally fluffy dinosaurs. (Credit Brian Choo)
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