Archaeopteryx is a Jurassic fossil bird that shares both bird and reptile features; it is widely accepted as the earliest and most primitive known bird.
Over the years, ten specimens of Archaeopteryx have been found, all in a limestone deposit near Solnhofen, Germany.
Some scientists see Archaeopteryx as climbing through the trees like a squirrel, following the idea that birds evolved from tree-dwelling gliders (the "trees down" hypothesis for the evolution of flight proposed by O.C.
Archaeopteryx continues to play an important part in scientific debates about the origin and evolution of flight.
Some consider Archaeopteryx to be a powerful piece of evidence that birds evolved from dinosaurs.
Other scientists see Archaeopteryx as running quickly along the ground, supporting the idea that birds evolved flight by running (the "ground up" hypothesis proposed by Samuel Wendall Williston).
The two camps, understandably, view differently where Archaeopteryx fits in the scheme between reptiles, or dinosaurs, and modern birds.
The Berlin specimen has been referred to as Archaeopteryx siemensii, the Eichstatt specimen as Jurapteryx recurva, the Munich specimen as Archaeopteryx bavarica, and the Solnhofen specimen was referred to as Wellnhoferia grandis.
So far, Archaeopteryx has perhaps produced as many questions as answers, and the latest findings on this fossil are unlikely to be the last word.
In 2004, scientists analyzing a detailed CT scan of Archaeopteryx's braincase concluded that its brain was significantly larger than that of most dinosaurs, indicating that it possessed the brain size necessary for flying.
The fine-grained limestone, which preserves detailed casts of features not often fossilized, is used by artists and printers for lithographic plates, thus the species name Archaeopteryx lithographica.