While there have been a number of threads on this topic, it remains a mystery to some of us.
Most people accept the theory that birds arose from theropod dinosaurs. But there seems to be a problem in that the fossil record does not present species of theropods that evolved bodies to accommodate flight, a prerequisite for evolving feathers to promote gliding, and later true flight. Coelurosauria is not the answer as they are also apex terrestrial bipeds, with the exception of some questionably positioned species. So please, anything with feathers is disqualified from discussion by the simple nature of these issues :
What we commonly know as theropods arose ca. 230 million years ago as an apex bipedal terrestrial predator, with a bottom heavy, top light morphology, with powerful legs, and shortened arms with three fingers. No one has derived a rational means, or reason, for how such an apex predator would evolve flight from a totally incompatible body format. Evolution requires a reason, i.e. a "driving force", for the appearance of biological traits, especially one so complicated as powered flight. The only thing a theropod had to worry about was a bigger theropod. That such animals would evolve flight seems more a flight of fantasy than of reality.
Some have referred to the transition to flight of such a terrestrial predator as the "ground-down" evolutionary sequence. If the bird-theropod relationship is correct, there should be intermediate forms in the fossil record revealing evolutionary changes in theropods to permit flight to arise. Such fossils should be trending toward a body format suitable for flight, and without feathers since flight would not yet have evolved. And these featherless theropods likely would have appeared ca. 200 mya, or earlier.
In a nutshell : Except for the reptilian features, ancient feathered "birds" do not look much at all like theropods.
Is anyone aware of fossils, prior to the appearance of feathers, that would allow such an unlikely creature as the initial bipedal terrestrial theropod to evolve flight from their poorly suited body format?
(Please, do not rain down a storm of feathered theropod stories. The question regards evidence for the transition in body formats that appears lacking in the fossil record, and almost certainly required for avian evolution to proceed.)
Most people accept the theory that birds arose from theropod dinosaurs. But there seems to be a problem in that the fossil record does not present species of theropods that evolved bodies to accommodate flight, a prerequisite for evolving feathers to promote gliding, and later true flight. Coelurosauria is not the answer as they are also apex terrestrial bipeds, with the exception of some questionably positioned species. So please, anything with feathers is disqualified from discussion by the simple nature of these issues :
What we commonly know as theropods arose ca. 230 million years ago as an apex bipedal terrestrial predator, with a bottom heavy, top light morphology, with powerful legs, and shortened arms with three fingers. No one has derived a rational means, or reason, for how such an apex predator would evolve flight from a totally incompatible body format. Evolution requires a reason, i.e. a "driving force", for the appearance of biological traits, especially one so complicated as powered flight. The only thing a theropod had to worry about was a bigger theropod. That such animals would evolve flight seems more a flight of fantasy than of reality.
Some have referred to the transition to flight of such a terrestrial predator as the "ground-down" evolutionary sequence. If the bird-theropod relationship is correct, there should be intermediate forms in the fossil record revealing evolutionary changes in theropods to permit flight to arise. Such fossils should be trending toward a body format suitable for flight, and without feathers since flight would not yet have evolved. And these featherless theropods likely would have appeared ca. 200 mya, or earlier.
In a nutshell : Except for the reptilian features, ancient feathered "birds" do not look much at all like theropods.
Is anyone aware of fossils, prior to the appearance of feathers, that would allow such an unlikely creature as the initial bipedal terrestrial theropod to evolve flight from their poorly suited body format?
(Please, do not rain down a storm of feathered theropod stories. The question regards evidence for the transition in body formats that appears lacking in the fossil record, and almost certainly required for avian evolution to proceed.)
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