Gregory Scott Paul: differenze tra le versioni
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comincio a sistemare, proseguo dopo |
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Riga 47:
:''Although some dinosaurs may have spent some time feeding in the water like moose or fishing cats, at most a few became strongly amphibious in the manner of hippos, much less marine as per seals and whales. The only strongly aquatic dinosaurs are some birds. The occasional statement that there were marine dinosaurs is therefore incorrect - these creatures of Mesozoic seas were various forms of reptiles that had evolved over the eons.'' (p. 14)
*Quando si credeva ancora che gli uccelli non derivassero dai dinosauri, si riteneva di conseguenza che il loro volo si fosse sviluppato tra gli animali arrampicatori che prima planavano e poi hanno sviluppato il volo potenziato. Questa ipotesi era avvalorata dal fatto che sappiamo che gli animali arboricoli potessero evolvere il volo potenziato con l'aiuto della gravità, come nel caso dei pipistrelli. Quando fu scoperto che gli uccelli discendono dai deinonicosauri, molti ricercatori cambiarono ipotesi e teorizzarono che i dinosauri corridori avessero imparato a volare dalla terra ferma,
:''When it was assumed that birds did not evolve from dinosaurs, it was correspondingly presumed that their flight evolved among climbers that first glided and then developed powered flight. This has the advantage that we know that arboreal animals can evolve powered flight with the aid of gravity, as per bats. When it was realized that birds descended from deinonychosaurs, many researchers switched to the hypothesis that running dinosaurs learned to fly from the ground up. This has the disadvantage that it is not certain whether it is practical for tetrapod flight to evolve among ground runners working against gravity. The characteristics of birds indicate that they evolved from dinosaurs that had first evolved as bipedal runners, and then evolved into long armed climbers. If the ancestors of birds had been entirely arboreal, then they should be semiquadrupedal forms whose sprawling legs were integrated into the main airfoil, like bats. That birds are bipeds whose erect legs are separate from the wings indicates that their ancestors evolved to run.'' (p. 52)
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