【越独】伞月伞越独寂静（共53只，3/27-22:45）（结帖）

dingxiaodanger

rtzgzdhr岁的他违背图瓦恶补图瓦莪白头温热

mh66

马上要考啦 多谢

tiancaichy

非常感谢！

coolorigin

楼主加油！就靠你了！

summer11223344

thanks for sharing！ thanks

liugang456654

鸟的羽毛，不知道是不是这个。网上找到的。
The Origin of Feathers

The proteins that make feathers in living birds are completely unlike the proteins that make reptilian scales today. Feathers originate in a skin layer deep under the outer layer that forms scales. It is very unlikely that feathers evolved from reptilian scales, even though that thought is deeply embedded in the minds of too many paleontologists. Feathers probably arose as new structures under and between reptile scales, not as modified scales. Many birds have scales on their lower legs and feet where feathers are not developed, and penguins have such short feathers on parts of their wings that the skin there is scaly for all practical purposes. So there is no real anatomical problem in imagining the evolution of feathers on a scaly reptilian skin. But feathers evolved in theropods as completely new structures, and any reasonable explanation of their origin has to take this into account.
Obviously, feathers did not evolve for flight. They evolved for some other function and were later modified for flight.

Feathers may have evolved to aid thermoregulation. The feathered Chinese theropods all have down, probably as insulation to keep their bodies at an even temperature. It would not matter whether they used their feathers to conserve heat in cold periods, or to keep heat out in hot periods, or both. In either case, insulation would have been useful.

The thermoregulatory theory for the origin of feathers is probably the most widely accepted one today, but it does have problems. Why feathers? Feathers are more complex to grow, more difficult to maintain in good condition, more liable to damage, and more difficult to replace than fur. Every other creature that has evolved a thermoregulatory coat, from bats to bees and from caterpillars to pterosaurs, has some kind of furry cover. There is no apparent reason for evolving feathers rather than fur even for heat shielding.

Furthermore, thermoregulation cannot account for the length or the distribution of the long feathers on Protarchaeopteryx or Caudipteryx. Short feathers (down) can provide good thermoregulation, but thermoregulation does not require long feathers, and it would not help thermoregulation very much to evolve long strong feathers on the arms and tail. So it is difficult to suggest that feathers evolved for thermoregulation alone. It would be better to think of another equally simple explanation.

I naturally prefer an idea that I developed years ago, with my colleague Jere Lipps. In living birds, feathers are for flying, for insulation, but also for camouflage and/or display. Lipps and I suggested that feathers evolved for display. The display may have been between females or between males for dominance in mating systems (sexual selection), or between individuals for territory or food (social selection), or directed toward members of other species in defense.

Living reptiles and birds often display for one or all of these reasons, using color, motion, and posture as visual signals to an opponent. Display is often used to increase apparent body size; the smaller the animal, the more effectively a slight addition to its outline would increase its apparent size. Lipps and I therefore proposed that erectile, colored feathers would give such a selective advantage to a small displaying theropod that it would encourage a rapid transition from a scaly skin to a feathery coat. Display would have been advantageous as soon as any short feathers appeared, and it would have been most effective on movable appendages, such as forearms and tail. (Display on the legs would not be so visible or effective.) Forearm display by a small theropod would also have drawn particular attention to the powerful weapons the theropod carried there, its front claws (Figure 13.1). The Chinese theropod Caudipteryx carried long feathers on its middle finger, between the two outside claws, and it could fold that middle finger away, with the feathers out of harm's way, during a strike.

The display hypothesis explains more features of the feathered theropods and the first bird Archaeopteryx than other hypotheses, with fewer assumptions. It explains completely the feather pattern: the evolution of long strong feathers on arms and tail.

Once they evolved, feathers could quickly have been co-opted for thermoregulation, and the down coat on the Chinese theropods may show that process. Down can only be for thermoregulation. Although down is not proof of warm blood, it is very strong evidence in favor of it. In living birds, down feathers are associated with the problem of heat loss for hatchlings.

saintone

thanks a lot. may you have well

熊宰

jkairup

oko jkairu

eooeooe

ding!