Glorified dinosaurs

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Next in line above the dromaeosaurs are the bizarre oviraptors. (walking dinosaur costume)These parrot-beaked beasts are very similar to archaeopterygians and dromaeosaurs in the neck, shoulder girdle, hand, and the hip’s ilium and ischium. They are more like birds than prior protobirds in the roof of the mouth, and in their very pneumatic skull bones. The ostrich-mimic ornithomimids also may belong in the protobird clade. Their braincases are quite birdlike, and they have the middle ear set in a shallow depression of the braincase. The roof of the mouth is rather avian in structure. At one time I thought ostrich-mimics were close relatives to tyrannosaurs, because the tails and legs in the advanced species of both are. extremely alike. But early ostrich-mimics are not nearly so tyrannosaur-like. (animatronic dinosaur)Even those who share characters differ in some subtle but key ways-for example, an L-shaped versus a straight central cannon bone. This is a classic case of parallelism in fast theropods. It is more likely, though still tenuous, that oviraptors and ornithomimids share a conunon, secondarily flightless ancestor. Exceptionally birdlike in the braincase, middle ear, roof of the mouth, and hind legs are the sickle-clawed troodonts (realistic dinosaur costume). Usually these are considered close relatives of dromaeosaurs, and as pro(obirds they are. But troodonts are too advanced to be really close dromaeosaur relatives. That hyperextendable second toes are present in archaeopterygians, dromaeosaurs, and troodonts suggests that the mainstream of flyng protobirds had them. Their predaceous and grounded offshoots retained them, while the nonpredatory oviraptors and ostrichmimics did not. Last among protobirds are the terrifically birdlike avimimids-their head is basically that of a bird, and the upper hand is fused into a single unit also just like a bird’s. Among the evidence indicating that Cretaceous protobirds were secondarily flightless, the avimimid’s tightly folding arms and fused wrist and hand bones must be considered some of the most telling.