While their presence is ambiguous if not nonexistent in the Jurassic, in the Early Cretaceous we do see the first definite signs of fully-developed birds. Animatronic dinosaur This is only five to twenty million years after Archoeoptery><. Perhaps the earliest are from the earliest Cretaceous of Romania-the flying Eurolimnornrs and Poloeocursornrs. l3 Found alongside some Archaeopreryar-like remains, Polaeocursornis is said to be a ratite, the group of flightless birds that includes present-day ostriches. I have doubts about the ratite claim. but if true then Paloeocursornrs is the most ancient modern bird, and the oldest flightless one as well. Another indication of a very early bird is a bit of a hind limb from China, around 135 million years in age.’a Named Gcnius, it may have been a primitive Hesperornrs-like diver; certainly, it is not a modernstyle shorebird as has been suggested. Soon after lived a bird described this year by Sanz, Bonaparte, and Lacasca in the Las Hoyas Formation of Spain; it looks like the most primitive true bird yet found. Then there is flying, Ichthyornis-like Ambforh”rs from the slightly younger Hauterivian-Barremian Age of Mongolia; it was described by Kurochkin in 1985. Finally, another Hesperornrs- type diver and Canadian wading bird’s tracks are found in sediments about thirtv million vears more recent than Archaeopter5x.
The appearance of highly developed birds so soon after ArchoeopterSx, and the presence of birdlike “Protoavis” way back in the Triassic, walking dinosaur costume cause many to speculate that true birds must have already been evolving much earlier in the Jurassic. This is possible. But as I explained earlier, there is evidence that advanced Jurassic birds did not exist. And besides, I do not understand what the fuss is about. Evolution can be gradual, but it can also move with awesome swiftness. If a suite of newly evolved adaptations is highly advantageous, then strongly favorable selective forces may be able to optimize them very rapidly. The first evolutionary radiation of dinosaurs seems to have had this astonishi., g quick-burst character. When dinosaurs bit the dust, mammals grew astoundingly in size and diversity of form in only five to ten million years. Especially pertinent to our problem is how the first birds and bats both appear in the fossil record suddenly and fully developed-in neither case are primitive flying grade forms known. Even “Protoavis,” with its many flightrelated adaptations, appears only a dozen or so million years after the first dinosaurs. That the major flying vertebrate groups always appear fully developed so suddenly is very suspicious.Realistic dinosaur costume It suggests that flight is so useful that once developed it is rapidly refined. The group’s “protoflyers” then quickly lose out to their superior relatives. In the case of birds, we have been lucky to find one of the protoflyers, Archoeopteryx. Besides, the distance between Archaeopteryx and full birds should not be exaggerated, for it does not take radical and tremendous alterations to make a protobird into a bird.