An as of yet undescribed specimen of Tianyulong, it's a tiny Ornithischian, and a late surviving representative of very early, primitive forms - as in, the earliest grandfathers of dinos like Iguanodon, Stegosaurus, Ankylosaurus, Triceratops - that whole group, the herbivores with plates and spikes and duck-bills.
Look at the contour around its body, you will see the remnant of the fluff-o-sphere, as a slight darker yellow shade. Once you spot it, look at how deeply fluffy this animal was! It's almost how you imagine a rodent, where the shape of the body becomes entirely obscured by all that fluff. The tail seems to start very fluffy, then slim up a bit, then poof out again towards the end.
This animal was the size of a cat, roughly, so the deep fluffy poof is warranted.
I'll say for the sake of clarification, that "wow, you're wrong!"-type vids, showing a "chicken-ized tyrannosaurus" are likely incorrect. Tyrannosaurids ARE inside the feathery theropod bracket, and small-to-medium Tyrannosaurs DID have feathers, famously the quite large Yutyrannus had thick feathers, feathered toes, and a thick eagle-like coat covering its neck. But Tyrannosaurus rex was twice that size, and more likely to overheat if covered in such a coating.
Tyrannosaurus would therefore, more likely exhibit feathers in a way that elephants or rhinos exhibit fur: They posess hair-growth, but it is undetectable by a quick glance.
Now - a young T. rex could indeed have been fully feathery, especially since younglings of animals often retain features seen in ancestral forms - and, of course, the animal would be much smaller, perhaps shedding its floof as it grows.
In short, it was probably similar to fur in mammals: the larger, the less, the smaller, the more poofy. Since dinos featherless default is a thick, scaly skin, that's what would be on the menu - feathers and/or scales, often both - just like birds today have scaly feet, for example.
A recent find shows that Sauropods, for example, had a huge variation in the scale patterns on a single individual, it would have robust, armor-like scales on its feet and ankles, for example, to protect against randomly kicking stuff, it had various types of patterns covering the body, and in some cases, tall, dragon-like spines following the neck, back and tail. These spines would be entirely keratinous, as there is zero bone-remains of such spines, so they would not be like crocodile-spines, which are part of the skeleton, but rather like a rhino-horn.
Thick, robust scales covering the body, are also known in some Theropods, especially the Abelisaurs, and actually ossified osteoderms (like crocodile spikes) are known in the Theropod Ceratosaurus. So, even in Theropods, a fully scaly, even spiny body existed, mostly among the more "primitive" types - but these MAY in fact be secondarily fluff-less, as in - their ancestors might have been fluffy.
Here's the kicker, see - Pterosaurs were all furry. Pterosaurs and Dinosaurs share very close recent ancestry - the so-called Ornithodirans, who split into Pterosauriforms and Dinosauriforms, all of them very small, very agile animals, swift like small bipedal cats. Here's where the question appears: Fluff is known in Pterosaurs, and it's known in primitive Ornithischians (so far not in primitive Theropods, and even less primitive Sauropods) - but if Pterosaur fluff and Ornithischian fluff become linked in a future discovery of Ornithodiran fluff - then it means ALL of Dinosauria falls inside the fluff-bracket, and any flufflessness beyond, would be secondary.
Anyway, nuff fluff for now, just admire the poof of little Tianyulong there! As well as its long, little squirrel tail!