Archaeopteryx (meaning "old wing" or "first bird"), is a bird-like dinosaurs that is transitional between non-avian feathered dinosaurs and modern birds. Archaeopteryx lived in the Late Jurassic around 150 million years ago, in what is now southern Germany during a time when Europe was islands in a shallow warm tropical sea, much closer to the equator than it is now. 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 mass of 1.8 to 2.2 lbs. Archaeopteryx feathers, although less documented than its other features, were very similar in structure and design to modern-day bird feathers. Despite the presence of numerous avian features, however, 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. As far as paleontologists can tell, birds evolved from feathered dinosaurs multiple times during the later Mesozoic Era (witness the four-winged Microraptor, which represented a "dead end" in bird evolution). In fact, modern birds are probably more closely related to the feathered theropods of the late Cretaceous period than to the late Jurassic Archaeopteryx. According to a recent analysis, the feathers of Archaeopteryx were structurally weaker than those of comparably sized modern birds, a hint that this dino-bird glided for short intervals rather than actively flapping its wings. Not all paleontologists concur, some arguing that Archaeopteryx actually weighed far less than the most widely accepted estimates, and was thus capable of brief bursts of powered flight. The reputation of Archaeopteryx as the first true bird is a bit overblown. True, this creature did possess a coat of feathers, a bird-like beak and a wishbone, but it also retained a handful of teeth, a long, bony tail, and three claws jutting out from the middle of each wing, all of which are extremely reptilian characteristics. For this reason, it's every bit as accurate to call Archaeopteryx a dinosaur as it is to call it a bird! If Archaeopteryx was in fact a glider rather than an active flier, this would imply a largely tree-bound, or arboreal, existence but if it was capable of powered flight, then this dino-bird may have been equally comfortable stalking small prey along the edges of lakes and rivers, like many modern birds.