It's probably the single most famous (and well-preserved) transitional form in the fossil record, but the bird-like dinosaur Archaeopteryx has mystified generations of paleontologists. Here are 10 facts you may (or may not) have known about Archaeopteryx. (See also a gallery of Archaeopteryx pictures.)
1. Archaeopteryx was discovered in the early 1860's...
Although an isolated feather was discovered in Germany in 1860, the first, headless fossil of Archaeopteryx wasn't unearthed until 1861, and it was only in 1863 that this creature was formally named (by the famous paleontologist Richard Owen). Ironically, it's now believed that that single feather may have belonged to an entirely different, but closely related, genus of dino-bird. (See a fossil history of Archaeopteryx.)
2. ....shortly after Charles Darwin published The Origin of Species.
In 1859, Charles Darwin shook the world of science to its foundations with his theory of natural selection. The discovery of Archaeopteryx, clearly a transitional form between dinosaurs and birds, did much to hasten the acceptance of evolutionary theory, though not everyone was convinced at the time (even Richard Owen was slow to change his views) and modern creationists continue to dispute the very idea of a "transitional form."
3. Archaeopteryx was about the size of a pigeon.
So great has been the impact of Archaeopteryx that many people mistakenly believe this dino-bird was much bigger than it actually was. In fact, Archaeopteryx measured only about 20 inches from head to tail, and the largest individuals didn't weigh much more than two pounds--about the size of a well-fed, modern-day pigeon. As such, it was much, much smaller than winged reptiles--aka pterosaurs--of the late Cretaceous period.
4. The fossils of Archaeopteryx are unusually well preserved.
The Solnhofen limestone beds, in Germany, are renowned for their exquisitely detailed fossils of late Jurassic flora and fauna. In the 150 years since the first Archaeopteryx fossil was discovered, researchers have unearthed 10 additional specimens, each of them revealing an enormous amount of anatomical detail. One of these fossils has since disappeared, presumably filched for a private collection.
5. Archaeopteryx shared its habitat with other ancient reptiles.
Archaeopteryx isn't the only creature to be preserved in the Solnhofen fossil beds. These deposits provide a frozen-in-time snapshot of late Jurassic Europe, and have yielded specimens of numerous prehistoric fish, the early pterosaurs Pterodactylus, Rhamphorhynchus and Anurognathus, and at least one tiny, non-feathered theropod dinosaur, Compsognathus.
6. Archaeopteryx possessed many dinosaur-like characteristics...
The reputation of Archaeopteryx as the first true bird is a bit overblown. True, this creature did possess a coat of feathers, a bird-like beak and a wishbone, but it also retained a handful of teeth, a long, bony tail, and three claws jutting out from the middle of each wing. For this reason, it's every bit as accurate to call Archaeopteryx a dinosaur as it is to call it a bird!
7. ...and wasn't directly ancestral to modern birds.
As far as paleontologists can tell, birds evolved from feathered dinosaurs multiple times during the later Mesozoic Era (witness the four-winged Microraptor, which represented a "dead end" in bird evolution). In fact, modern birds are probably more closely related to the feathered theropods of the late Cretaceous period than to the Jurassic Archaeopteryx. (See the article Was Archaeopteryx a Bird or a Dinosaur?)
8. The feathers of Archaeopteryx were unsuited to powered flight...
According to a recent analysis, the feathers of Archaeopteryx were structurally weaker than those of comparably sized modern birds, a hint that this dino-bird glided for short intervals rather than actively flapping its wings. Not all paleontologists concur, some arguing that Archaeopteryx actually weighed far less than the most widely accepted estimates, and was thus capable of brief bursts of powered flight.
9. ...meaning that Archaeopteryx may have lived in trees.
Even today, the lifestyle of Archaeopteryx remains a mystery. If this dino-bird was in fact a glider rather than an active flier, this would imply a largely tree-bound existence--but if it was capable of powered flight, then Archaeopteryx may have been equally comfortable stalking small prey along the edges of lakes and rivers, like many modern birds. (Whatever turns out to be the case, it's not unusual for small creatures of any type--birds, mammals or lizards--to live in trees.)
10. Archaeopteryx had a relatively sluggish metabolism.
A recent study concludes that Archaeopteryx hatchlings required almost three years to mature to adult size, a slower pace than comparably sized modern birds. What this implies is that, while Archaeopteryx may well have possessed a primitive warm-blooded metabolism, it wasn't nearly as energetic as its modern relatives, or even contemporary theropod dinosaurs (another hint that it may have been incapable of powered flight).