Scientists are minutely examining a fossil discovered nearly 160 years ago. This object, perhaps one of the best known of its kind ever found, lay in a bed of limestone in Germany for somewhere in the region of 150 million years. And after all this time, researchers have made a startling new discovery that completely upsets the consensus about what this ancient remnant represents.
But just what were those scientists studying? It was a fossilized feather, in fact, the oldest ever to be discovered. And the paper the team published in Nature in February 2019 outlined a startling new theory about this storied feather. The piece of plumage has exercised the minds of paleontologists ever since it was discovered 160 years ago, so this was an important breakthrough.
It was a German paleontologist, Hermann von Meyer, who came across the feather in the early 1860s. He was examining limestone rocks near the German town of Solnhofen in Bavaria, a region well-known for its abundance of fossils. And the limestone, dating back to the Jurassic era, was to yield much more than just a single feather.
Indeed, during the same period the fossilized skeleton of a creature that appeared to combine features normally found in dinosaurs with others similar to present-day birds was also unearthed. This was a tremendously exciting find, since it pushed back the dates of the evolution of birds by millions of years. Many scientists believed that the fossil was the remains of the very earliest of prototypical birds known to humankind.
Von Meyer subsequently gave the fossil feather a species name: Archaeopteryx lithographica. The first part comes from classical Greek with archaeos (“ancient”) and pteryx (“feather”). The species also has another name, Urvogel, which is German for first bird. And then came another hugely significant discovery at Solnhofen.
When Von Meyer was on the verge of releasing his report about the feather, the fossil bones of Archaeopteryx were discovered. These were unearthed in the limestone beds that had contained the feather, so naturally enough the assumption was that the feather and the bones were likely from the same animal.
The Natural History Museum in London, England, paid 700 pounds sterling for the fossil not long after it was discovered and has been home to these Archaeopteryx bones ever since. The museum’s experts date the fossil to approximately 150 million years ago. And at that time, the region of Germany where the fossils of both the feather and the animal were discovered was a very different place than it is today.
The period when the Natural History Museum specimen of Archaeopteryx lived is called the Tithonian, and it came towards the end of the Jurassic era. Back then, Europe was a series of islands and located nearer the Equator than it is now, on a latitude similar to that of Florida’s. As a result, the climate was probably quite hot and dry.
The Jurassic limestone that preserved the Archaeopteryx fossils was created by soil with a high lime content sinking to the bottoms of warm-water pools. This fine mud and the way the rocks were formed created conditions that are ideal for the preservation of fossils. While the Solnhofen stone has been a rich source of fossils of various dinosaurs, though, only Archaeopteryx shows evidence of feathers.
What’s more, after that initial discovery of a single feather, over the years the Solnhofen limestone has yielded further sets of Archaeopteryx fossils. That first specimen of the animal’s body found soon after the feather is called the “London specimen.” The second set of bones discovered was the most complete, and it goes by the name of the “Berlin specimen.”
A farmer called Jakob Niemeyer found this Berlin specimen in the mid-1870s in the Solnhofen limestone. It was subsequently bought from him by a bar-owner and displayed in his inn. Niemeyer is said to have spent the proceeds of his fossil sale on a cow.
This Berlin Archaeopteryx lays claim to being the most perfectly formed of all the specimens found to date. It’s has a complete skull, and much of the rest of the skeleton is also present. What’s more, the impression left by the feathers is quite clear. So, along with that first feather discovered by Von Meyer, it now seemed that science had at its disposal the almost complete skeleton of the animal that the plumage belonged to.
Unsurprisingly, one man who was especially interested in the discovery of Archaeopteryx was Charles Darwin. His groundbreaking work on evolution, On the Origin of Species, had been completed just a couple of years before Archaeopteryx was found. And Darwin was in no doubt about the importance of these fossils that appeared to link dinosaurs and birds.
Indeed, in later editions of On the Origin of Species, Darwin added an important passage about Archaeopteryx. It seems that he saw quite clearly that this transitional fossil was a strong piece of evidence supporting his, at the time, revolutionary theories of how different species had come to evolve over time.
In his fourth edition of On the Origin of Species, Darwin wrote, “Not long ago, paleontologists maintained that the whole class of birds came suddenly into existence during the Eocene period.” The Eocene dates back to a mere 56 to 34 million years ago, in contrast to the age of Archaeopteryx, which is around 150 million years old. So, this shows how significant the Archaeopteryx discovery was in terms of dating the evolution of birds.
“But now we know… that strange bird, the Archaeopteryx, with a long lizard-like tail, bearing a pair of feathers on each joint, and with its wings furnished with two free claws, has been discovered in the [sedimentary rock] of Solnhofen,” Darwin continued. “Hardly any recent discovery shows more forcibly than this how little we as yet know of the former inhabitants of the world.”
As you’ve just read, Darwin gave a brief description of this strange combination of a dinosaur and a bird. And, in life, it must have been a strikingly strange creature indeed. The specimens of Archaeopteryx that have come to light show that the animal weighed around 2 pounds. That means it would have been somewhere between a raven and a chicken in size.
Anatomically, Archaeopteryx had some similarities to an order of dinosaurs called the coelurosaurs. They were meat eaters and among their number was the formidable Tyrannosaurus. Indeed, initially, the only obvious distinction between Archaeopteryx and members of the coelurosaur order of dinosaurs was the feathers clearly apparent in the fossil record.
Although Archaeopteryx and modern birds have their similarities, there are also key differences. Archaeopteryx, for example, had a relatively lengthy tail as well as clearly defined teeth, characteristics absent in contemporary birds. What’s more, Archaeopteryx had three distinct fingers mounted on their wings with claws on each one, whereas modern birds have fused fingers.
But, the feathers aside, what makes Archaeopteryx most closely resemble what we would recognize as a bird were its two wings. They were like the wings of current birds except that those three clawed fingers protruded from the front. And Archaeopteryx feathers grew not just from the wings, but like today’s birds also on the body and part of the way down its legs.
So, with those wings and the attached feathers, the obvious question is: could Archaeopteryx fly? On that, scientists have differing views – and it depends on what you mean by “fly.” Some researchers believe that this half-bird, half-dinosaur creature could indeed power itself through the air just as we see most modern bird species do.
But other scientists are of the view that Archaeopteryx could probably only glide rather than fly in a purposeful way by beating its wings. One paleontologist, Christian Foth of Switzerland’s University of Fribourg takes a middle view. Addressing the question of how Archaeopteryx moved through the air, he spoke to the Live Science website in March 2018.
“The contour feathers in the wing and on the side of the tails of Archaeopteryx have an asymmetric shape, which is usually related to a higher aerodynamic performance,” Foth explained. “Thus, it is very likely that Archaeopteryx could fly, but it is hard to judge if it was a flapper or a glider.”
Foth also pointed out that the animal’s shoulder anatomy probably curtailed its ability to flap its wings. In addition, its foot bones meant it likely couldn’t grip and perch like modern birds. His conclusion from this evidence was that “we think that it could perform a simple flapping flight over a very short distance, maybe in relation to hunting or escape behavior.”
So now we have a picture of an animal combining aspects of the dinosaurs and modern birds, a creature likely capable of some sort of flight. But what kind of life would this creature have led 150 million years ago? Well, Archaeopteryx was found on land but its nearby environment would most likely have included heavily saline pools. Those would have been linked to warm seas of tropical character and little depth.
The deeper waters of these lagoons would have been poisonous, so what life there was – perhaps fish and some plants – would have been near the surface. Insects such as dragonflies and pterosaurs, flighted dinosaurs unrelated to birds, would have flown above the tepid waters. Other fossil animals have been discovered in the limestone beds that formed at the lagoon bottoms, but they were likely washed in by storms from other areas.
Scientists have scant information about the diet of Archaeopteryx, however. Nonetheless, we know that the species was a meat-eater, so it’s probable that it subsisted on small creatures such as mammals, insects and reptiles. It probably captured its victims in its teeth, although it could also have overpowered them with the three claws it wielded on each wing.
But how did specimens of Archaeopteryx end up dead in the mud sediment at the bottom of those lakes to be preserved as fossils? One scenario is that an animal might have become trapped unawares in bad weather and then been rendered unable to fly. It would subsequently have sunk into the waters of a pool.
Indeed, that theory about being surprised and overwhelmed by heavy weather is backed up by another facet exhibited by each of the Archaeopteryx fossils. Without exception, they show developmental signs of being a juvenile. This may explain why these animals were caught out: they simply lacked the experience of a more mature creature in dealing with bad weather.
Once at the bottom of the lake, the body of an Archaeopteryx would have been gradually covered by succeeding layers of sediment that was rich in lime. With the passage of sufficient time, that mud turned to hard Solnhofen limestone and preserved the creature’s form. Then there was a mere 150-million-year wait until a human discovered the bones – or even a single feather!
As we’ve seen, the very first evidence of the existence of Archaeopteryx came with Von Meyer’s discovery of just one feather 160 years ago. But scientists have had some doubts about the provenance of that feather almost since it was found. Indeed, when the first skeleton of Archaeopteryx – the London specimen – was described by famed paleontologist Richard Owen in 1863, he clearly had some reservations about the idea that the feather belonged to Archaeopteryx.
In fact, Owen called the London specimen Archaeopteryx macrarua rather than Archaeopteryx lithographica, the name Von Meyer had given to the owner of his single feather. Owen used a different name than that coined by Von Meyer in order to recognize the fact that the feather and the London specimen could have been from different creatures.
And the story of that single feather discovered by Von Meyer has become even murkier over the years. For example, an illustration of the feather made not long after it was found clearly shows it to have a calamus. This is the scientific term for a feather’s quill. That’s the pointed part at the end of a feather that was once used as a writing instrument before modern pens were invented.
But if you take a look at the fossil as it is today, no quill is visible to the naked eye. And that matters very much when it comes to matching up this feather with the skeletal remains. If it were present, the tip of the quill could be compared to feathers actually attached to one of the Archaeopteryx bone sets. Without it, however, this is impossible. As a result, confirmation that the feather belonged to an Archaeopteryx becomes problematic.
So, how could this quill have gone missing over the past 160 years when it was described in detail and even drawn not long after the feather was discovered? Well, there are various theories to explain this anomaly. The feather’s quill could perhaps have been obliterated by over-zealous cleaning of the limestone slab. Alternatively, over-exposure to sunlight might be the culprit.
Nonetheless, the reason why the quill has disappeared over the decades remains unclear. And figuring out where this single feather fitted into the story of Archaeopteryx was severely handicapped by this missing quill. Even the use of UV imaging and X-ray technologies failed to reveal it.
But an international team of scientists led by Thomas Kaye, director of the Foundation for Scientific Advancement (USA), decided it was time to perform a new analysis of the feather fossil. For this examination, they would use state-of-the art technology to see if they could reveal traces of the quill not visible to the naked eye.
Kaye and his colleagues utilized a technique called laser-stimulated fluorescence to search for the absent quill. And this did indeed allow them to detect traces of it. With that evidence now available, the researchers were able to declare with confidence that this feather was not part of the known plumage of Archaeopteryx.
That conclusion still leaves the possibility that the feather could be one that matches up to plumage not present on the known Archaeopteryx fossils, of course. But it also opens up the exciting prospect that it comes from a different species altogether. Indeed, if this isn’t an Archaeopteryx feather, perhaps 150 million years ago there was a wide variety of plumed creatures flitting above the tropical lagoons of what’s now Southern Germany.
Speaking to the Science Daily website in February 2019, one of Kaye’s colleagues, the University of Hong Kong’s Dr. Michael Pittman, said, “My imaging work with Tom Kaye demonstrates that important discoveries remain to be made even in the most iconic and well-studied fossils.” And now we’re left to contemplate the possibility that the skies above the Solnhofen limestone beds were once filled with all kinds of strange fluttering creatures, half-dinosaur, half-bird.