经济学人83:蛇颈龙的家族生活

 　　Science and Technology Prehistoric 1 reptiles 2 A loving mother

　　科技 史前爬行动物 慈母
　　Family life in plesiosaurs
　　蛇颈龙的家族生活
　　THE Mesozoic land was dominated by dinosaurs 3.
　　中生代时期，恐龙统治着陆地。
　　At sea, though, the most abundant reptiles were the ichthyosaurs and plesiosaurs.
　　但是在海里，最繁盛的爬行动物要属鱼龙和蛇颈龙了。
　　Roughly speaking, these animals filled the ecological 4 niches 6 now occupied by toothed cetaceans such as dolphins and killer 7 whales.
　　大致上讲，这些动物填补了由现代齿鲸目动物海豚和虎鲸所占据的生态龛位。
　　Ichthyosaurs, indeed, looked somewhat like dolphins, though plesiosaurs—with their long necks and diamond-shaped paddles—were unlike anything now alive.
　　鱼龙看上去的确有点象海豚，但拥有长颈和菱形鳍状前肢的蛇颈龙却与现存的任何动物不相类似。
　　Ichthyosaurs also resembled cetaceans in another way: unlike most living reptiles, which lay eggs, they gave birth to live young.
　　鱼龙与鲸类动物还有另一点相似之处：大多数现存的爬行动物靠产卵繁殖，而鱼龙是通过怀胎产子的。
　　For years, palaeontologists have wondered if the same was true of plesiosaurs.
　　数年来，古生物学家一直想知道蛇颈龙是否也通过怀胎方式繁殖后代。
　　Now they have found out that it was—but with an interesting twist.
　　如今他们证实了这一点——但却是以一种有趣的方式。
　　Robin 8 O'Keefe of Marshall University in West Virginia has analysed a plesiosaur fossil found in Kansas in 1987, which palaeontologists had suspected was a pregnant female about 4.7 metres (15 feet) long, but which had not been cleaned up and studied until last year.
　　西弗吉尼亚州马歇尔大学的罗宾·奥基夫对1987年在堪萨斯州发现的蛇颈龙化石进行了分析，此前，古生物学家一直怀疑它是一条身长4.7米（15英寸）雌性怀孕蛇颈龙， 但直到去年才将其清理和研究完毕。
　　As he reports in Science, he found an array of tiny bones, apparently 9 belonging to a small specimen 10 of the same species, in the fossil's abdominal 11 cavity (see above; the extra bones are highlighted).
　　奥基夫在《科学》杂志报告中指出，在蛇颈龙化石腹腔内（额外的骨骼被高亮显示）发现了一些小骨骼阵列，它们显然是属于同类物种的小标本。
　　It is unlikely that these were the remains 12 of a meal because the bones are not broken down in the way that would be expected if they were partly digested.
　　这些小骨骼不可能是食物的残渣，因为如果它们是被部份消化的其它动物的骨骼，那么它们的断裂方式应该研究人员所预想的方式相同，但结果却不是。
　　Instead, Dr O'Keefe believes he has discovered evidence that plesiosaurs, too, gave birth to live young.
　　反过来，奥基夫博士相信他已发现了蛇颈龙同样靠胎生繁殖的证据。
　　What is more, all the baby bones come from a single individual, estimated to have been 1.5 metres long.
　　此外，所有幼蛇颈龙的骨骼皆来自于单一的个体，身长估计有1.5米。
　　Ichthyosaurs and other contemporary viviparous species, by contrast, gave birth to multiple offspring.
　　对比之下，鱼龙和其它现代胎生物种可以生育多个后代。
　　The fetus's level of development indicates that it was at most two-thirds mature.
　　从蛇颈龙幼胎的发育水平来看，它最多有三分之二的成熟度。
　　Had it survived to birth it would have been about 1.8 metres in length, and about one and a half times as heavy (relative to parental 13 weight) as the offspring of other viviparous species of the time.
　　如真能够成功分娩，幼蛇颈龙的身长可能为1.8米左右，体重大约是同时期其它胎生物种后代的1.5倍（相对于父母的重量）。
　　That it was so heavy, and also alone, is of great interest.
　　蛇颈龙幼胎超重且单独的个体引起了古生物学家的极大兴趣。
　　Georges Cuvier, an early palaeontologist, made his reputation by predicting the anatomies 14 of newly discovered fossil species from scant 15 evidence, such as single bones.
　　早期古生物学家乔治·居维叶能在实据不足的情况下（如单一的骨骼）预测出新发现的化石物种的躯干结构，这使他在业界声名显著。
　　He did so by applying to fossils the principles of comparative anatomy 16, asking what light the body shapes of living animals could cast on the shapes of creatures from the past.
　　之所以能做到这点是因为他将对比解剖学的规则应用于化石样本并探寻现存动物的体形对古代动物的体形有什么样的启发借鉴作用。
　　Many modern palaeontologists try to do something similar, except that what they reconstruct is behaviour.
　　许多现代古生物学家除了重现古代动物的行为外，也在尝试做着同样的事情。
　　Dr O'Keefe has performed such an analysis on his find.
　　奥基夫博士已将这种分析应用于他的发现。
　　He starts from a fundamental observation about reproduction: you can go for quantity or quality.
　　他的实验开始于对繁殖现象的基本观察： 你能选择数量或质量。
　　Having one child at a time is the ultimate expression of quality.
　　每次只生育一胎是追求质量的最终体现。
　　It implies huge parental investment in the offspring since, if you lose it, you lose everything.
　　它意味着父母在后代身上的巨大投入，一旦失去了这个幼子也就等于失去了一切。
　　Often, too, it implies membership of a social group, within which favours can be traded to spread the load of parenthood.
　　它也常常意味着社会群体的成员身份，在这个社会群体中，幼子关爱可以通过利益交换得到以减轻父母的负担。
　　Most speculatively 17, it might even imply a degree of intelligence—for the most intelligent mammals and birds are generally those that live in groups.
　　从最大程度上猜测，它甚至可能意味着动物的智商程度——生活在群体中的哺乳动物和鸟类通常是最聪明的。
　　All this is a lot to load on a single fossil, of course.
　　当然仅凭这个单一化石，古生物学家未免猜想得太多了。
　　But it would make sense.
　　但它却能够说明问题。
　　It would mean plesiosaurs not only occupied a similar ecological niche 5 to whales, but behaved like them, too.
　　它将意味着蛇颈龙不仅占据着与鲸鱼相似的生态龛位，其行为方式也与鲸鱼相仿。