揭开翼龙性别及生殖之谜

Unravel the Mystery of the Pterosaur Sex and Reproduction

翼龙是已知最早演化为强有力飞行能力的脊椎动物。最近发现的一成年雌性翼龙与她的蛋保存在一起的化石,提供了翼龙性别的直接证据,并加深了对这些已绝灭的飞行动物生殖生物学的理解。这一雌性达尔文翼龙的发现使我们对这一物种有了更多的了解。新的发现证实了雄性具有相对小的骨盆和大的头骨脊,而雌性则具有大的骨盆和头骨无脊。对蛋化石的详细研究显示翼龙的生殖策略,如多数研究者以前怀疑的那样,与鸟类的是不一样的,而与鳄类或者其它的爬行动物一样。与以前发现的具有胚胎的翼龙蛋的壳一样,这一研究也证实与其母体相比,蛋相对小而软且具有羊皮纸一样的壳。很明显,蛋产下来后,会从周围环境中吸收水分,从而在这一时期增加其大小和重量。这意味着母体不必在蛋里投入过多的水分,而这一点可能对于飞行来说是相当有利的:在母体中小而轻利于携带。这也暗示了雌性达尔文翼龙像爬行动物那样很少关注她们的蛋,这些蛋被埋着而从周围吸收营养。

Pterosaurs are a group of flying reptiles which are the earliest vertebrates known to have evolved powerful flight capability. A recently discovered adult female pterosaur fossil preserved together with her egg provides the direct evidence of sex in pterosaurs and affords insights into the reproductive biology of these extinct fliers. The discovery helps us learn more about male Darwinopterus by comparing previously discovered fossils with the new female fossil. The new findings confirm that the males had relatively small pelvises and large cranial crests whereas the females had much larger pelvises but no cranial crests. Detailed studies of the fossilized egg imply that, as most researchers had previously suspected, the pterosaur＇s reproductive strategies were not like those of birds but more like those of crocodiles or other reptiles. It is shown that the egg is relatively small in comparison with the pterosaur＇s body and that it was likely soft and covered in a parchment-like shell, similar to the pterosaur embryo found before. The eggs could significantly conduct uptake of water after oviposition from their environment, and they probably increased in size and mass during this period. This means that the adult did not have to invest too much water in the egg, which could have been quite advantageous： Less material investment in the egg and less mass to carry around during the production of the egg in the female＇s that Darwinopterus females buried their eggs like reptiles, paying little attention to nutrients from the ground body. This also suggests them as they absorbed