Did birds evolve from dinosaurs? Fossils of largest feathered dinosaur hint at ancestry

It has long been debated that birds were once dinosaurs with feathers, or, in other words, birds evolved from their giant ancestors- the feathered dinosaurs.

In a recent fossil study, palaeontologists termedYutyrannus hauli as the largest feathered dinosaur. The fossil is around ninemetres long and weighs close to 1,400 kilogrammes with partial or complete feathers (which is still up for debate). This might be the largest feathered dinosaurs, but the modern birds have closer resemblance to a theropod group called- Tyrannoraptors. This group includes everybody’s favourite bipedal predator, the Tyrannosaurs rex. or T. rex.

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The T. rex fossils are believed to have had patches of skin with few feathers on them, much like with a scaly reptile-like skin that is more commonly associated with softer bird-like feathers.

But recent evidence show that Yutyrannus hali is the biggest dinosaur discovered till date with feather. Yutyrannus hali,literally meaning “beautiful feathered tyrant”, was discovered in 2012 after a fossil was purchased from a dealer.

The “beautiful feathered tyrant” was big and fuzzy and lived 125 million years ago

Whether Yutyrannus huali was partially or completely feathered is contentious, but we do know that it had proto feathers that differ from modern feathers.

Proto feathers have long filaments (around 20 centimeters, according to the Australian Museum) that lacked the barbs, barbules, and hooks we see in modern feathers, but are thought to have formed a shaggy coat that would’ve enabled Yutyrannus to keep warm in cold climates.

When it comes to comparing proto and modern feathers of Yutyrannus and T. rex, researchers believe that Yutyrannus lived around 125 million years ago during the early Cretaceous period, and by the time T. rex arrived, the feathers saw an evolution.

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It is estimated that baby T. rex would’ve been the size of a terrier, and it too may have sported a coat of fuzzy proto feathers. Then, as it reached its teenage growth spurt years (when they triple in size in less time), the feathers may have reduced to small patches that could've been useful in mating rituals.

One reason to doubt whether adult T. rex were covered in featherscomes down to their physiology. As T. rex grew, its volume increased significantly more than its surface area (skin). In other words, metabolically speaking, it wouldn’t have made sense to be covered in feathers as it would’ve been too hot.

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T. rex’s issue wasn’t getting cold but quite the opposite. When it was a baby and it had high surface area to body volume ratio that would have benefited from the warmth of feathery jacket. That is likely why feathers evolved in the first place, as a form of thermoregulation for small animals with big surface areas that made it hard for them to retain the heat made by their bodies.

This approach likely didn’t suit the giant T.rex, however, and so the feathers were lost in some groups but retained by others, including the dinosaurs we share this planet with today.

(With inputs from agencies)