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modern giraffe is thought to represent the upper limit of tracheal length possible with functional bellows style lungs. But where does that leave the brachiosaurus, whose neck, at 28 feet, was longer than the entire giraffe? It would have to have unidirectional lungs more like that of a bird for it to have ever evolved such a neck.

Moving on to theropods, we begin to see some major changes in body structure and projected behavior. Theropods walk on two legs, their front limbs taking a variety of shapes, and their diet ranging from the herbivorous therizinosaurs to the carnivorous tyrannosaurs. A simple look at skeletal structure revealed hollow bones, though they lack the sophisticated air sacks of modern bird bones. Additionally, in the 1970s, testing ratio of upper to lower leg length against those of living animals with upright stances led to some startling conclusions. With calves much longer than their thighs, theropods had the legs of runners, not of slow lumbering lizards of silent movies. All evidence points to them running along the ground to chase down their next meal. Such an active lifestyle is not available to a traditionally cold-blooded animal. Snakes, lizards and crocodiles, pay a price of relative inactivity for the lack of ability to maintain their body temperature.

Having all this good evidence that theropods were warm blooded, scientists postulated the need for an insulated covering to protect help the dinosaurs maintain their body heat. This theory was answered with a series of discoveries in the 1990s of theropod skeletons surrounded by the impressions of primitive barbed keratin structures without a middle vein. Anyone with a down blanket knows how warm primitive barbed keratin structures can keep you. So this discovery provided explanations for both the insulation of the theropods, and the gradual evolution of feathers before their flight specialization.

However far we have come, it is in this next small family of theropods that we literally begin to see the bird within the dinosaur. Eumaniraptors are the clade that brings us velociraptors of Jurassic Park fame and their larger cousin the deinonychus. As the name suggests, eumaniraptors are characterized by large snatching arms, but another interesting development was a pubis rotated back partially to point straight down, like that of archaeopteryx. In addition, to put more strength and mobility into those large hands, eumaniraptors had a furcula, a primitive version of what's commonly

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