National Geographic

Fluffy Dinosaur Raises Questions About the Origin of Dinofuzz

Almost twenty years after fluffy little Sinosauropteryx hopped onto the scene, the existence of feathery dinosaurs is no longer much of a surprise. Paleontologists have found evidence of body coverings from “dinofuzz” to flight feathers on a score of non-avian dinosaur species, ranging from the pigeon-sized, magpie-patterned Anchiornis to the 30-foot long Yutyrannus. But despite this flood of fossil discoveries, paleontologists are still puzzling over the bigger questions behind the plumage. Among the most pressing is when these downy splashes of fluff and fuzz first evolved. A newly-named dinosaur found in Siberia only complicates the question.

Late last year, at the annual Society of Vertebrate Paleontology meeting in Los Angeles, experts and amateurs crowded into a presentation hall to see Royal Belgian Institute of Natural Sciences paleontologist Pascal Godefroit present a new feathered dinosaur. The buzz around the specimen, fueled by the conference program, was that the dinosaur in question was an ornithischian.

Most feathery and fluffy dinosaurs found so far are theropods. This is a major dinosaur subgroup that includes birds and their close relatives, as well as carnivorous terrors like Ceratosaurus and weirdos like Therizinosaurus, going all the way back to where this “beast footed” lineage split from all other dinosaurs. But the dinosaur Godefroit was set to unveil was all the way on the other side of the dinosaur family tree. Ornithischians included the armored, shovel-beaked, and horned dinosaurs, among others, and were as distantly-related to birds as it was possible to be while still being dinosaurs. That’s what made a fluffy ornithischian so strange.

Paleontologists had found two different ornithischians with peculiar body coverings before. In 2002 Gerald Mayr and colleagues announced bristle-like structures jutting from the tail of Psittacosaurus, an early horned dinosaur, and in 2009 Xiao-Ting Zheng and coauthors described Tianyulong, an archaic form of dinosaur called a heterodontosaurid with a mane of similar quills. Together, these animals raised two alternatives: either dinosaurs evolved feather-like body coverings multiple times, or wispy body coverings were an ancestral trait that went all the way back to the last common ancestor of all dinosaurs.

Godefroit’s animal promised to add one more data point to this cluster of flashy ornithischians. Sadly, he couldn’t present his animal during the SVP meeting. Excited dinomaniacs, myself included, trudged out of the hall and into other concurrent sessions. From a geologic perspective, though, the wait for the details hasn’t been long. Today, Godefroit and colleagues have presented their peculiar dinosaur, named Kulindadromeus zabaikalicus, in the pages of Science.

The locality where Kulindadromeus was found. Photo credit: Th. Hubin/RBINS.

The locality where Kulindadromeus was found. Photo credit: Th. Hubin/RBINS.

This new dinosaur is already known from a wealth of material. A pair of bonebeds, estimated to be between 169 and 144 million years old, yielded “six partial skulls and several hundred disarticulated skeletons” of Kulindadromeus scattered through the remnants of a Jurassic lake. The bones showed the five-foot-long dinosaur to be a neornithischian, a bipedal herbivore that was not so archaic as Tianyulong but not so specialized as the hadrosaurs or horned dinosaurs. And some of these skeletons not only included different types of scales, but what Godefroit and colleagues interpret as “avianlike feathers.”

In terms of typical dinosaur tubercles, Kulindadromeus had hexagonal scales on its lower legs, rounded scales around the hand and ankle, and rows of large scales along the tail. But the fossils also preserved a trio of feathery structures. Single filaments surrounded the dinosaur’s head, torso, and back, while the dinosaur’s upper arms and legs were covered in multi-filament plumes and the dinosaur’s lower leg sported “ribbon-shaped elements” that have not been seen in any other species so far.

Wispy structures that covered part of Kulindadromeus. But are they feathers? From Godefroit et al., 2014.

Wispy structures that covered part of Kulindadromeus. But are they feathers? From Godefroit et al., 2014.

The question is whether these fluffy structures are true feathers or fluffy imitations. This has major implications for when true feathers and their immediate forerunners evolved in dinosaurs. If the dinofuzz on Kulindadromeus really is equivalent to that borne by theropods like Sinosauropteryx, then the beginnings of feathers probably coincided with the origin of dinosaurs. If the structures are superficially the same, but not truly equivalent, then feather-like structures either evolved more than once or diverged from some earlier, as-yet-unseen type of integument.

For the moment, there’s still no way to distinguish between these alternative scenarios. At a basic anatomical level paleontologists have yet to discern whether the structures on Psittacosaurus, Tianyulong, and Kulindadromeus can truly be called feathers. Not to mention the need for better fossils of older dinosaurs, close to where the major lineages split, to follow feather origins, as well as a more refined understanding of the circumstances under which fluff, fuzz, and bristles are likely to be preserved.

Fluffy juvenile Apatosaurus? It's not out of the realm of possibility. Art by Niroot Puttapipat.

Fluffy juvenile Apatosaurus? It’s not out of the realm of possibility. Art by Niroot Puttapipat.

But while the headline that “all dinosaurs had feathers” stretches the evidence too far, Godefroit and colleagues are correct that dinosaurs probably sported a variety of filamentous body coverings in addition to scales.

Feathers or scales aren’t mutually exclusive – look at the feet of a chickadee or pigeon sometime – but are different kinds of body coverings that non-avian dinosaurs wore in startling combinations. This opens up tantalizing possibilities for familiar dinosaurs whose outer appearances are still poorly known. Imagine Allosaurus with whisker-like wisps around its face to help it better nab prey, or an Apatosaurus with a shock of fluff running down its back. I have no doubt that as paleontologists uncover more and more dinosaurs with weird, fuzzy body coverings, our image of what a dinosaur is will become ever-stranger.

Reference:

Godefroit, P., Sinitsa, S. Dhouailly, D., Bolotsky, Y., Sizov, A., McNamara, M., Benton, M., Pagina, P. 2014. A Jurassic ornithischian dinosaur from Siberia with both feathers and scales. Science. 345, 6195: 451-45

There are 9 Comments. Add Yours.

  1. Zach Miller
    July 24, 2014

    Well, another potentially fluffy ornithischian is always welcome, but those wispy structures look very different from what you see in basal theropods, Psittacosaurus, and Tianyulong. Perhaps ornithischians had some version of protofeathers but then took them down a different developmental pathway?

  2. David Moscato
    July 24, 2014

    Very interesting. As we find more feathered dinos, I find myself wondering how many dinosaurs we know *weren’t* feathered.
    How exactly are these feathers preserved? Are they sediment impressions a la Archaeopteryx, or are they filamentous structures on the bones themselves?
    And following that question – are there dinosaurs that we’ve found that likely didn’t have feathers? Any dinosaur fossils where we would expect feathers to be preserved (if they were present) but they weren’t? Perhaps we could put together data on feathered vs. not-feathered dinosaurs.

  3. Mark
    July 24, 2014

    Thinking of dinosaurs and the inclusion of protofeathers has me wondering if the adaptation was triggered by a cooling climate or a climate that began to have sudden shifts in temperature. Feathers in birds today help regulate body temperature and it does seem to be an easier and quicker way to adapt animals of the past to varying temperatures, rather than a change in their primitive circulatory systems. Maybe a partial explanation to their extinction maybe climate related, affecting their food supply and body temperatures where nature couldn’t started the attempt at modification, but ran out of time for most of them.

  4. Harold
    July 24, 2014

    Its starting to seem more and more likely that proto feathers or fuzz go back deep in time and the idea that it goes way back to the root of the dinosaur lineage seems most parsimonious with so many different lineages sporting some type of feathery structure. As an amateur I’m wondering whether fuzz like that seen here might ultimately be related to our own mammalian hairs. Or is this already ruled out by molecular or dna evidence?

  5. Marcos K. Pinheiro
    July 24, 2014

    This is an amazing find! And I agree what you said in the end of this article, Brian. And for now, they found: an Edmontosaurus regalis with a comb-like crest; a Deinocheirus skull with a hadrosaur-like beak (despite being an ornithomimosaur); and a Tarbosaurus specimen with a dewlap!

  6. Pascal Godefroit
    July 25, 2014

    I broke my knee two days before my SVP presentation at L.A.: it was the starting point of the Kulindadromeus Malediction!

  7. Michael Balter
    July 25, 2014

    Nice, thorough and balanced discussion, Brian!

  8. peter
    July 26, 2014

    ‘Feathers’ might even predate the dinosaurs. The Pterosaurs are occasionally (often) regarded as fluffed, so ‘feathers’ might be a feature of Ornithodira. The emergende of Ornithodira might approach the early Triassic – cold if I’m not mistaken.

  9. Patrick O’Connor
    July 30, 2014

    If the tilt of the Earth was as extreme then as it is now, earlier dry land life would have developed techniques and biological protections against temperature differences between night and day and the seasons, excluding maybe in the equatorial regions. Forms of hair and feathers would probably have developed much sooner than the fossil record suggests.

Add Your Comments

All fields required.

Related Posts