For Fossil Study, "Bird" is Still the Word

Today is National Fossil Day, acknowledging the great importance of these ancient remains. Experts have long known that fossils tell the story of a time before man, and even foreshadow things to come, which is why they are so crucial to scientific investigation.

And these days they do a lot more than just tell us "dinosaurs were here." The modern study of fossils has graduated far beyond simple awe for the prehistoric. Researchers use fossils to trace the evolution of life's ancestors, looking to birds in particular in an effort to better understand how evolution shapes our world.

Dinos-of-a-Feather Evolve Together

When one thinks "fossil," the towering majesty of a Tyrannosaurus rex skeleton is likely the first thing that comes to mind. That's because paleontology, the study of things prior to the Holocene epoch (which encompasses the entirety of human existence), is best known for digging up big old dinosaur bones to wow the kids and leave adults daydreaming.

However, these days, paleontologists have been focusing their attention on smaller and delicate fossils - namely feathers.

This fascination first began at the start of the 1860s, when paleontologists discovered first the impression of a single feather, and then an entire skeleton of Archaeopteryx - a 150-million-year-old fossil called the "London Specimen," and "first bird."

At the time of the feathered creature's discovery, few experts considered it a dinosaur, confident that they were looking at an example of the early birds that flitted around the world's king lizards. After all, dinosaurs didn't have feathers, right?

But by the 1960s, general acceptance of the theory of evolution and additional fossil evidence (including a number of other Archaeopteryx discoveries) had the world thinking that perhaps the "first bird" was really an example of a dinosaur on its way to becoming one of our feathery friends. (Scroll to read on...)

Just this year, another fossil specimen of Archaeopteryx was discovered, and this one was found covered in feathers from head-to-toe. And bizarrely, few of these feathers really implied "flight."

"It probably didn't fly like a bird at all - maybe like a turkey if it really tried," Mark Norell, a paleontologist at the American Museum of Natural History, told National Geographic.

Norell has been studying the incredibly well preserved plumage of this specific specimen for years, and recently came to the conclusion that feathers, not flight, came first in dinosaurs.

That was after he found long "pennaceous" feathers - similar to those seen in flying birds today - covering the creature in the most nonsensical of places.

The paleontologist theorized that these feathers developed first for other purposes, such as for a mating display, and only were adapted for flight when coincidental placement led to some Archaeopteryx achieving semi-flight when chasing prey or trying to escape predators.

But knowing that feathers came first is only half the battle. Another study released this year revealed that bird-like predators, called theropods, were not the only dinosaurs that boasted feathers. Ten million years before Archaeopteryx even existed, a ponderous plant-eater called Kulindadromeus zabaikalicus trudged through prehistoric swamps with a thick coat of bristle-like feathers, likely used for insulation, and a number of ribbon-like feathers for display.

Study author Pascal Godefroit of the Royal Belgian Institute of Natural Sciences explained that "there's nothing like it in modern birds."

Only the Small Survive

Skeletal structure and unique feathering alone is enough to tell researchers that Kulindadromeus is no avian ancestor, but its discovery is helping push paleontologists away from their feather fixation.

Size, not feathers, may have been what made birds' ancestors unique enough to radically evolve.

That's at least according to a theory introduced to the scientific community last August.

"Birds evolved through a unique phase of sustained miniaturization in dinosaurs," lead author Michael Lee, from the University of Adelaide's School of Earth and Environmental Sciences and the South Australian Museum, argued in a recent statement. (Scroll to read on...)

"Being smaller and lighter in the land of giants, with rapidly evolving anatomical adaptations, provided these bird ancestors with new ecological opportunities, such as the ability to climb trees, glide and fly," he added. "Ultimately, this evolutionary flexibility helped birds survive the deadly meteorite impact which killed off all their dinosaurian cousins."

So while our feathered swamp dwellers were quite literally stuck in the mud when a cataclysmic meteorite came, birds' tiny ancestors where dashing and flitting to the safest hidey-hole they could find.

Back to the Bones

Within the last two months, it seems that the study of bird evolution has come full-circle. No longer are researchers staring at feathers, but instead they are taking a second look at bones. In a recent meta-analysis of the raptor-like theropods, researchers found a number of uniquely avian traits that were slipping into dinosaur design long before Archaeopteryx.

Early traits like wing development, wishbones, and yes, even feather development, were trickling into the dinosaur gene pool at such a gradual rate that most Jurassic avian descendants looked no different from other dinosaurs.

However, "once it came together fully, it unlocked great evolutionary potential that allowed birds to evolve at a super-charged rate," Steve Brusatte, of the University of Edinburgh's School of GeoSciences, said in a statement.

His findings are complemented by an additional study published just last month in the journal PLOS Biology. (Scroll to read on...)

Alexander Vargas, who leads the ontology and phylogeny lab at the University of Chile in Santiago, found that early dinosaurs boasted a tiny bone in their wrist called the pisiform. When theropods evolved to be bipedal, the bone eventually disappeared, as they were making less regular use of their wrists.

However, as arms and wrists became wings, the bone saw a quick return, and can even be seen in modern birds. Vargas argues that it would be hard for modern birds to regain a bone their ancestors never had, but if their ancestors truly were dinosaurs, then this rapid development of the pisiform makes sense.

Still, the idea that a bone can disappear and reappear in evolution is something that a lot of experts will struggle to wrap their heads around. Some may argue that even if a bone has little use, it won't simply vanish, as bones like the whale pelvis have long been seen as useless to the animals, and yet still exist.

However, Nature World News recently reported how the hip bone may actually still be sexually selected for in whales, as a larger pelvis can support and control larger reproductive organs with deft.

In the case of bird evolution, paleontologists and other experts may never be able to fully explain it. However, with the help of an ever-growing fossil record, investigators are learning more about life, past and current, than Charles Darwin may have ever thought possible.