Archaeopteryx

***Archaeopteryx*** (/ˌɑːrkiːˈɒptərɪks/; lit. 'old-wing'), sometimes referred to by its German name, **"*Urvogel*"** (lit. *Primeval Bird*), is a genus of avian dinosaurs. The name derives from the ancient Greek ἀρχαῖος (*archaīos*), meaning "ancient", and πτέρυξ (*ptéryx*), meaning "feather" or "wing". Between the late 19th century and the early 21st century, *Archaeopteryx* was generally accepted by palaeontologists and popular reference books as the oldest known bird (member of the group Avialae). Older potential avialans have since been identified, including *Anchiornis*, *Xiaotingia*, and *Aurornis*.

*Archaeopteryx* was roughly the size of a raven, with broad wings that were rounded at the ends and a long tail compared to its body length. It could reach up to 0.5 m (1 ft 8 in) in body length and 0.7 m (2 ft 4 in) in wingspan, with an estimated mass of 0.5 to 1 kg (1.1 to 2.2 lb). *Archaeopteryx* feathers, although less documented than its other features, were very similar in structure to modern-day bird feathers. Despite the presence of numerous avian features, *Archaeopteryx* had many non-avian theropod dinosaur characteristics. Unlike modern birds, *Archaeopteryx* had small teeth, as well as a long bony tail, features which *Archaeopteryx* shared with other dinosaurs of the time.

*Archaeopteryx* lived in the Late Jurassic around 150 million years ago, in what is now southern Germany, during a time when Europe was an archipelago of islands in a shallow warm tropical sea, much closer to the equator than it is now. Despite their small size, broad wings, and inferred ability to fly or glide, *Archaeopteryx* had more in common with other small Mesozoic dinosaurs than with modern birds. In particular, they shared the following features with the dromaeosaurids and troodontids: jaws with sharp teeth, three fingers with claws, a long bony tail, hyperextensible second toes ("killing claw"), feathers (which also suggest warm-bloodedness), and various features of the skeleton.

These features make *Archaeopteryx* a clear candidate for a transitional fossil between non-avian dinosaurs and birds. Thus, *Archaeopteryx* plays an important role, not only in the study of the origin of birds, but in the study of dinosaurs. It was named from a single feather in 1861, the identity of which has been controversial. That same year, the first complete specimen of *Archaeopteryx* was announced. Over the years, ten more fossils of *Archaeopteryx* have surfaced. Despite variation among these fossils, most experts regard all the remains that have been discovered as belonging to a single species, although this is still debated.

*Archaeopteryx* was long considered to be the beginning of the evolutionary tree of birds. However, in recent years, the discovery of several small, feathered dinosaurs has created a mystery for palaeontologists, raising questions about which animals are the ancestors of modern birds and which are their relatives. Most of these eleven fossils include impressions of feathers. Because these feathers are of an advanced form (flight feathers), these fossils are evidence that the evolution of feathers began before the Late Jurassic. The type specimen of *Archaeopteryx* was discovered just two years after Charles Darwin published *On the Origin of Species*. *Archaeopteryx* seemed to confirm Darwin's theories and has since become a key piece of evidence for the origin of birds, the transitional fossils debate, and confirmation of evolution.