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Science and Technology Prehistoric reptiles A loving mother
科技 史前爬行動(dòng)物 慈母
Family life in plesiosaurs
蛇頸龍的家族生活
THE Mesozoic land was dominated by dinosaurs.
中生代時(shí)期，恐龍統(tǒng)治著陸地。
At sea, though, the most abundant reptiles were the ichthyosaurs and plesiosaurs.
但是在海里，最繁盛的爬行動(dòng)物要屬魚(yú)龍和蛇頸龍了。
Roughly speaking, these animals filled the ecological niches now occupied by toothed cetaceans such as dolphins and killer whales.
大致上講，這些動(dòng)物填補(bǔ)了由現(xiàn)代齒鯨目動(dòng)物海豚和虎鯨所占據(jù)的生態(tài)龕位。
Ichthyosaurs, indeed, looked somewhat like dolphins, though plesiosaurs—with their long necks and diamond-shaped paddles—were unlike anything now alive.
魚(yú)龍看上去的確有點(diǎn)象海豚，但擁有長(zhǎng)頸和菱形鰭狀前肢的蛇頸龍卻與現(xiàn)存的任何動(dòng)物不相類(lèi)似。
Ichthyosaurs also resembled cetaceans in another way: unlike most living reptiles, which lay eggs, they gave birth to live young.
魚(yú)龍與鯨類(lèi)動(dòng)物還有另一點(diǎn)相似之處：大多數(shù)現(xiàn)存的爬行動(dòng)物靠產(chǎn)卵繁殖，而魚(yú)龍是通過(guò)懷胎產(chǎn)子的。
For years, palaeontologists have wondered if the same was true of plesiosaurs.
數(shù)年來(lái)，古生物學(xué)家一直想知道蛇頸龍是否也通過(guò)懷胎方式繁殖后代。
Now they have found out that it was—but with an interesting twist.
如今他們證實(shí)了這一點(diǎn)——但卻是以一種有趣的方式。
Robin 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.
西弗吉尼亞州馬歇爾大學(xué)的羅賓·奧基夫?qū)?987年在堪薩斯州發(fā)現(xiàn)的蛇頸龍化石進(jìn)行了分析，此前，古生物學(xué)家一直懷疑它是一條身長(zhǎng)4.7米（15英寸）雌性懷孕蛇頸龍， 但直到去年才將其清理和研究完畢。
As he reports in Science, he found an array of tiny bones, apparently belonging to a small specimen of the same species, in the fossil's abdominal cavity (see above; the extra bones are highlighted).
奧基夫在《科學(xué)》雜志報(bào)告中指出，在蛇頸龍化石腹腔內(nèi)（額外的骨骼被高亮顯示）發(fā)現(xiàn)了一些小骨骼陣列，它們顯然是屬于同類(lèi)物種的小標(biāo)本。
It is unlikely that these were the remains of a meal because the bones are not broken down in the way that would be expected if they were partly digested.
這些小骨骼不可能是食物的殘?jiān)驗(yàn)槿绻鼈兪潜徊糠菹钠渌鼊?dòng)物的骨骼，那么它們的斷裂方式應(yīng)該研究人員所預(yù)想的方式相同，但結(jié)果卻不是。
Instead, Dr O'Keefe believes he has discovered evidence that plesiosaurs, too, gave birth to live young.
反過(guò)來(lái)，奧基夫博士相信他已發(fā)現(xiàn)了蛇頸龍同樣靠胎生繁殖的證據(jù)。
What is more, all the baby bones come from a single individual, estimated to have been 1.5 metres long.
此外，所有幼蛇頸龍的骨骼皆來(lái)自于單一的個(gè)體，身長(zhǎng)估計(jì)有1.5米。
Ichthyosaurs and other contemporary viviparous species, by contrast, gave birth to multiple offspring.
對(duì)比之下，魚(yú)龍和其它現(xiàn)代胎生物種可以生育多個(gè)后代。
The fetus's level of development indicates that it was at most two-thirds mature.
從蛇頸龍幼胎的發(fā)育水平來(lái)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 weight) as the offspring of other viviparous species of the time.
如真能夠成功分娩，幼蛇頸龍的身長(zhǎng)可能為1.8米左右，體重大約是同時(shí)期其它胎生物種后代的1.5倍（相對(duì)于父母的重量）。
That it was so heavy, and also alone, is of great interest.
蛇頸龍幼胎超重且單獨(dú)的個(gè)體引起了古生物學(xué)家的極大興趣。
Georges Cuvier, an early palaeontologist, made his reputation by predicting the anatomies of newly discovered fossil species from scant evidence, such as single bones.
早期古生物學(xué)家喬治·居維葉能在實(shí)據(jù)不足的情況下（如單一的骨骼）預(yù)測(cè)出新發(fā)現(xiàn)的化石物種的軀干結(jié)構(gòu)，這使他在業(yè)界聲名顯著。
He did so by applying to fossils the principles of comparative anatomy, asking what light the body shapes of living animals could cast on the shapes of creatures from the past.
之所以能做到這點(diǎn)是因?yàn)樗麑?duì)比解剖學(xué)的規(guī)則應(yīng)用于化石樣本并探尋現(xiàn)存動(dòng)物的體形對(duì)古代動(dòng)物的體形有什么樣的啟發(fā)借鑒作用。
Many modern palaeontologists try to do something similar, except that what they reconstruct is behaviour.
許多現(xiàn)代古生物學(xué)家除了重現(xiàn)古代動(dòng)物的行為外，也在嘗試做著同樣的事情。
Dr O'Keefe has performed such an analysis on his find.
奧基夫博士已將這種分析應(yīng)用于他的發(fā)現(xiàn)。
He starts from a fundamental observation about reproduction: you can go for quantity or quality.
他的實(shí)驗(yàn)開(kāi)始于對(duì)繁殖現(xiàn)象的基本觀察： 你能選擇數(shù)量或質(zhì)量。
Having one child at a time is the ultimate expression of quality.
每次只生育一胎是追求質(zhì)量的最終體現(xiàn)。
It implies huge parental investment in the offspring since, if you lose it, you lose everything.
它意味著父母在后代身上的巨大投入，一旦失去了這個(gè)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.
它也常常意味著社會(huì)群體的成員身份，在這個(gè)社會(huì)群體中，幼子關(guān)愛(ài)可以通過(guò)利益交換得到以減輕父母的負(fù)擔(dān)。
Most speculatively, it might even imply a degree of intelligence—for the most intelligent mammals and birds are generally those that live in groups.
從最大程度上猜測(cè)，它甚至可能意味著動(dòng)物的智商程度——生活在群體中的哺乳動(dòng)物和鳥(niǎo)類(lèi)通常是最聰明的。
All this is a lot to load on a single fossil, of course.
當(dāng)然僅憑這個(gè)單一化石，古生物學(xué)家未免猜想得太多了。
But it would make sense.
但它卻能夠說(shuō)明問(wèn)題。
It would mean plesiosaurs not only occupied a similar ecological niche to whales, but behaved like them, too.
它將意味著蛇頸龍不僅占據(jù)著與鯨魚(yú)相似的生態(tài)龕位，其行為方式也與鯨魚(yú)相仿。
