The Marxburg and Eichstatt specimens were discovered during the 20th century, and the Haarlem specimen that languished misattributed until 1970 was actually discovered in 1855, five years before a solitary feather was found in the Solnhofen Limestone of Southern Germany.
Distinguishing features in this animal include the presence of gastralia, or ventral ribs, the lack of a pygostyle, and the reversed hallux, or first toe, which leads many to think it was descended from the bipedal Coelophysis or Deinonychus.  The Marxburg and Eichstatt specimens were discovered during the 20th century, and the Haarlem specimen that languished misattributed until 1970 was actually discovered in 1855, five years before a solitary feather was found in the Solnhofen Limestone of Southern Germany. FTP name this reptile of the Jurassic period, the oldest known species generally accepted as a bird.
Distinguishing features in this animal include the presence of gastralia, or ventral ribs, the lack of a pygostyle, and the reversed hallux, or first toe, which leads many to think it was descended from the bipedal Coelophysis or Deinonychus.  
Archaeopteryx lithographica