Archaeopteryx-missing link

Archaeopteryx lived during the early Tithonian stage of the Jurassic Period, around 150.8 to 148.5 million years ago. Most of the specimens of Archaeopteryx that have been discovered come from the Solnhofen limestone in Bavaria, southern Germany, which is a lagerstatte, a rare and remarkable geologicalformation known for its superbly detailed fossils.

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 500 millimetres (20 in) in body length, with an estimated weight of 0.8 to 1 kilogram. Archaeopteryx feathers, although less documented than its other features, were very similar in structure and design to modern-day bird feathers. However, despite the presence of numerous avian features, Archaeopteryx had many 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. Because it displays a number of features common to both birds and dinosaurs, Archaeopteryx has often been considered a link between them. In the 1970s, John Ostrom, following T. H.Huxley's lead in 1868, argued that birds evolved within theropod dinosaurs and Archaeopteryx was a critical piece of evidence for this argument; it had a number of avian features, such as a wish bone, flight feathers, wings and a partially reversed first toe, and a number of dinosaur and theropod features. For instance, it has a long ascending process of the ankle bone, interdental plates, an obturator process of the ischium, and long chevrons in the tail. In particular,Ostrom found that Archaeopteryx was remarkably similar to the theropod family Dromaeosauridae.