It all began with a single feather. On Sept. 30, 1861, the German paleontologist Christian Erich Hermann von Meyer published his description of a jaw-dropping new find. Fossil feathers were unheard of at the time, yet somebody had pulled one out of a limestone quarry near Solnhofen, Bavaria.
Von Meyer named the animal it belonged to Archaeopteryx lithographica. His choice was apt; the first part of that name (i.e., Archaeopteryx) means "ancient wing."
By sheer coincidence, von Meyer's description came out less than two years after Charles Darwin published his landmark book, "On the Origin of Species." Archaeopteryx immediately entered the discourse about evolution and natural selection.
More material was on the way. By late 1861, the fossilized skeleton of a birdlike creature with a long, bony tail — something modern birds lack — had emerged from the Bavarian countryside. Parts of the body were surrounded by feather impressions.
A Feather in Darwin's Cap
That fossilized skeleton we mentioned was soon bought on behalf of what's now the Natural History Museum in London, England. Aficionados call that Archaeopteryx fossil the "London specimen."
Much better-known is the "Berlin specimen." Currently displayed at the Natural History Museum of Berlin, Germany, it was found near the Bavarian town of Eichstätt in 1876. Unlike its British-held counterpart, this Archaeopteryx features a complete skull.
And what a skull! Whereas modern birds are toothless, the Berlin specimen has a mouth full of small, conical teeth. Another trait that set Archaeopteryx apart from today's birds are the three clawed fingers showcased on each hand.
In total, bony remains from around 12 individual Archaeopteryx have turned up. All this material hails from Bavaria, in Jurassic rock deposits that are around 150 million years old.
There's a debate about whether the skeletal fossils represent the same animal as von Meyer's original feather. Separate studies published in the journal Nature in 2019 and 2020 reached different conclusions on the matter.
Leaving the Nest
The second toe on each foot was hyperextensible; Archaeopteryx could hold the digits at an upright angle even while standing. Chances are, this kept the claws on both toes from wearing down too fast.
Opinions differ, but a different set of toes may have been somewhat opposable. If so, perhaps Archaeopteryx could grasp things with its feet.
Judging by the available fossils, Archaeopteryx grew to be around 21 inches (53 centimeters) long with a 2-foot (60-centimeter) wingspan. That wasn't necessarily the creature's maximum size, though. Some Archaeopteryx specimens might represent juvenile animals.
According to a 2009 bone structure study, Archaeopteryx grew up at a slower rate than most living birds do. By the same paper's estimates, mature adults would've weighed about 1.8 to 2.2 pounds (822 to 1,009 grams) — making them about the size of common ravens.
Archaeopteryx might've shared something else with ravens, by the way. That feather von Meyer wrote about in 1861 is thought to be a covert feather, meaning it probably covered the bases of larger feathers. Traces left behind by microscopic pigment structures reveal some feathers from Archaeopteryx-bearing deposits — including von Meyer's—were either completely or partially black.
Black feathers offer some advantages. White pelicans, wood storks and lots of other birds have black-tipped wings. That's because the pigment responsible for this color has the pleasant side effect of strengthening flight feathers.
Ravens also use their dark plumage to regulate body temperature; black feathers absorb heat from the sun, which can then be dissipated by passing winds. Counterintuitively, having black feathers is a good way to keep cool.
By nature, feathers are multipurpose tools. Whether it's flightless or not, a bird's coat can help it attract mates and regulate body temperature.
Just like modern birds, Archaeopteryx had feathers that varied in size and shape across different regions of the body. One specimen has the imprints of both asymmetrical, 3.9 to 4.5-inch (9.9 to 11.4-centimeter) tail feathers — and smaller, symmetrical leg feathers measuring 1.5-1.7 inches (4-4.5-centimeters) long.
Back in the Jurassic, this dinosaur may have looked like it was wearing shaggy trousers.
For more than a century-and-a-half now, the world's been wondering if Archaeopteryx could fly.
The dinosaur lived at a time when Bavaria was a subtropical archipelago full of lagoons and barrier islands. The south German limestones where Archaeopteryx is found comprise a "lagerstatten," an area with exceptionally well-preserved fossils.
Unrelated flying reptiles called pterosaurs appear in the same lagerstatten. So do the bones of Compsognathus, a small theropod featured in "The Lost World: Jurassic Park." Fossilized beetles, dragonflies, jellyfish, real fish, crustaceans and swimming reptiles round out the ensemble. Scientists think Archaeopteryx ate smaller animals like insects.
Artists often depict Archaeopteryx perched on elevated tree branches. However, 150 million years ago, low-lying shrubs were probably more common than trees in this part of the world.
Trees factor into the large discussion about how theropod flight evolved. According to one proposed scenario (the "trees-down" hypothesis), the direct ancestors of the first flighted birds were tree-climbers who'd glide from branch to branch.
Was the Sky the Limit?
Archaeopteryx's climbing skills — or lack thereof — are a bone of contention. But many scientists now think it was a half-decent flyer.
In 2018, a team led by paleontologist Dennis Voeten examined the wing bones of three different Archaeopteryx. Next, their proportions were compared with the arms from 69 different animals — from extant birds to nonavian dinosaurs like Allosaurus to the good old American alligator.
Judging by its bones, the team concluded Archaeopteryx could probably fly for short bursts, rather like modern pheasants and turkeys. However, the dinosaur's shoulder anatomy would've made it incapable of flapping its wings the same way extant birds do.
All birds are theropods, but not all theropods were birds. Experts disagree about how Archaeopteryx should be classified. Some see it as a basal bird, others think it had more in common with Velociraptor and its cousins.
We've come a long way since 1861. At dig sites around the world, dinosaurs with feathers and similar body coverings are constantly emerging. Many predate Archaeopteryx by tens of millions of years.
And let's not ignore the recent discovery of tiny theropods with "bat-like" wings. This unexpected new development just goes to show that the emergence of flight in dinosaurs was a complex affair. Archaeopteryx got the conversation rolling. Who knows where it'll go next?