Courtesy Photo by Zang Hailong (via Nature)A huge one-and-a-half ton theropod discovered recently in China is further shaking up our old ideas of dinosaurs being oversized scaly lizards. The fossilized remains of Yutyrannus huali, a 130 million year-old tyrannosaur uncovered in the Liaoning fossil beds show evidence of a fuzzy coating of feathers on several areas, e.g. the tail, hip, foot, neck and arm. Yutyrannus huali is a distant relative of Tyrannosaurus rex(there is some contention about this) which didn’t evolve until much later in the Cretaceous period. Evidence of feathers has been found on smaller dinosaurs including the basal tyrannosauroid Dilong but these are the first clues that larger dinosaurs had feathers. Three nearly complete and well-articulated skeletons of Y. huali - an adult and two juveniles were found in the Lower Cretaceous Yixian Formation of Liaoning Province in northeast China. The adult is quite large, being nearly 30 feet in length and estimated to have weighed in life around 3000 pounds! The two juveniles weighed around 1200 pounds. All show evidence of having filamentous feather. Large animals today, such as elephants, rhinos, and hippos are somewhat hairless and tend not to need insulation for retaining heat because of their size and the ratio of surface area of skin to their masses. Whether Yutyrannus huali’s well-known descendent Tyrannosaurus rex had any plumage remains a mystery. T. rex was six times as massive as its ancestor, and arrived on the scene 60 million years later in the Late Cretaceous when the climate was warmer. But all it takes to change that is some new fossil to come to light. Generally, it’s thought that feathers first appeared as a means of insulation, species identification, or for attracting mates long before they evolved for use in flight. Today, birds are considered the descendents of small theropods dinosaurs called dromeosaurids. The discovery of Yutyrannus huali adds new clues and additional mystery to our conception of how dinosaurs appeared in life. The new study by Chinese vertebrate paleontologist Xu Xing and his co-researchers appears in the science journal Nature.
Why the "yee-haw," JGordon?
Man, I don't know. Because "dinosaur feathers" sounds lot like "horse feathers," and no one in the history of humanity has ever uttered "horse feathers" without also shouting "yee-haw" in the same five-minute window. And because dinosaurs and their feathers are exciting, so why not toss a little yee-haw in there.
It doesn't matter, really. What matters is that you check out all these cool images of Cretaceous period feathers preserved in amber.
Now a new fossil has emerged from China that is complicating the picture. Tianyulong confuciusi was a small, two-legged plant-eater that lived in northeastern China about 130 million years ago. Its recently-discovered fossil included clear signs of feathers. This is nothing unusual—lots of dino fossils, especially from this part of China, have feathers.
What is unusual is that Tianyulong is not related to any previously known feather-bearing dinosaur. Not even remotely. All previously know dino feathers come from theropods, the two-legged meat-eaters like T. rex. Tianyulong was a type of hadrosaur—sometimes known as a “duck-billed dinosaur.” And the last time hadrosaurs and theropods shared a common ancestor was 230 million years ago!
This discovery raises several intriguing possibilities:
1. Perhaps feathers evolved very early in dinosaur history, far earlier than we now suspect. If the very first dinosaurs had feathers, then all other dinosaurs could inherit them, even after the various branches of the dino family tree split up and went their separate ways. But if that’s true, then why have we not found feathers on more dino skeletons?
2. Perhaps feathers evolved twice—once in the theropods, and once in the hadrosaurs. That would be pretty unusual. Right now, there seems to be no information on whether these new feathers are very similar to previously-known feathers, or completely different.
3. One thing has always bugged me about the whole bird-dino link. All dinosaurs fall into two major groups: those with hips shaped like those found in modern lizards, and those with hips shaped like those found in modern birds. But all the previous bird-like features, including feathers, come from the lizard-hipped group. Seems odd to me that nature would evolve bird-like hips twice. Maybe—just maybe—birds evolved from the bird-hipped dinosaurs.
Now, there’s tons of other evidence besides just hips to link birds to theropods, so nobody is going to be re-writing the bird family tree any time soon. All we can do is keep our eyes peeled for more interesting discoveries.