Schlein (More Than One, p. 1047, etc.), subtitling this ""The Story of Archaeopteryx,"" tells how in 1861 the fossil remains of an unusual Jurassic-era creature were found in Germany. The skeleton resembled that of a very small dinosaur but the outline of feathers that covered its body remained in the stone, indicating that it was a bird. The classification of the creature--as a bird (that looked like a dinosaur), or a mammal (that looked like a bird)--has been hotly debated to this day. The book further discusses possible ancestors of archaeopteryx--pterosaurs, small dinosaurs, small reptiles, coelosaurs (""hollow-tailed reptiles""), or other primordial birds--that would aid in the classification process. Despite the lack of answers, readers will relish the mystery; Hallett's excellent drawings and diagrams clarify and add interest to an already informative and challenging book.