南極出土的化石顯示恐龍滅絕時，就連南方大陸上的生物都無法倖免於難

原文網址：www.sciencedaily.com/releases/2016/05/160526091956.htm

Antarctic fossils reveal creatures weren't safer in the south during dinosaur extinction

南極出土的化石顯示恐龍滅絕時，就連南方大陸上的生物都無法倖免於難

A study of more than 6,000 marine fossils from the Antarctic shows that the mass extinction event that killed the dinosaurs was sudden and just as deadly to life in the polar regions.
一則對超過6000具從南極出土的海洋生物化石進行的研究顯示，突如其來消滅恐龍的大滅絕事件對極區生物而言同樣地致命。

Previously, scientists had thought that creatures living in the southernmost regions of the planet would have been in a less perilous position during the mass extinction event than those elsewhere on Earth.

之前科學家認為在大滅絕事件發生時，相較於地球上其他地方，居住在地球最南方的生物的處境應該沒那麼岌岌可危。

The research, published today in the journal Nature Communications, involved a six-year process of identifying more than 6,000 marine fossils ranging in age from 69- to 65-million-years-old that were excavated by scientists from the University of Leeds and the British Antarctic Survey on Seymour Island in the Antarctic Peninsula.

此篇刊登於今日《自然通訊》(Nature Communications)期刊的研究由里茲大學及英國南極調查所的科學家進行。在為期六年的研究過程中，他們從南極半島中的西摩島挖掘並辨識出超過6000具海洋生物的化石，它們的年代介於6900萬至6500萬年前。

This is one of the largest collections of marine fossils of this age anywhere in the world. It includes a wide range of species, from small snails and clams that lived on the sea floor, to large and unusual creatures that swam in the surface waters of the ocean. These include the ammonite Diplomoceras, a distant relative of modern squid and octopus, with a paperclip-shaped shell that could grow as large as 2 metres, and giant marine reptiles such as Mosasaurus, as featured in the film Jurassic World.

這是世界上對此年代的海洋化石進行的最大規模採集作業之一。他們蒐羅的物種種類可謂包羅萬象，從在海床上生活的小型海螺和蚌殼，到在海水表層泅游的罕見大型生物。後者包括Diplomoceras菊石，牠們是現代烏賊及章魚的古代遠親，身上迴紋針狀的甲殼可以長到2公尺之長；還有巨型海洋爬蟲類，像是電影「侏儸紀世界」中大放異彩的中龍。

With the marine fossils grouped by age, the collection shows a dramatic 65-70% reduction in the number of species living in the Antarctic 66 million years ago -- coinciding exactly with the time when the dinosaurs and many other groups of organisms worldwide became extinct at the end of the Cretaceous Period.

將這些海洋生物化石以年代進行分類後，這些樣品顯現出生活在南極的物種數目在6600萬年前急遽下降了65%至70%。這個時間點跟在白堊紀末期時，全世界恐龍以及許多種類的生物滅絕的時間點不謀而合。

James Witts, a PhD student in the University's School of Earth and Environment and lead author of the new research paper said: "Our research essentially shows that one day everything was fine -- the Antarctic had a thriving and diverse marine community -- and the next, it wasn't. Clearly, a very sudden and catastrophic event had occurred on Earth.

此篇新研究論文的第一作者，里茲大學地球與環境學院的博士生James Witts說：「大體而言，我們的研究成果描繪出的圖像顯示某天一切仍然如昔，南極擁有相當生氣蓬勃且多樣的海洋生物族群，但在下一刻一切都變了調。無庸置疑地，地球上發生了一件極具破壞力的突發事件。」

"This is the strongest evidence from fossils that the main driver of this extinction event was the after-effects of a huge asteroid impact, rather than a slower decline caused by natural changes to the climate or by severe volcanism stressing global environments."

「從化石得到的證據強烈指出這起滅絕事件的主因是大型小行星撞擊造成的後續效應，而非自然氣候變遷，或者是劇烈火山爆發導致全球環境惡化造成的緩慢衰亡。」

The study is the first to suggest that the mass extinction event was just as rapid and severe in the polar regions as elsewhere in the world.

這項研究首度提出如同世上其他地區，大滅絕事件在極區發生的速度也是相當地迅速且致命。

Previously, scientists had thought that organisms living near the Poles were far enough away from the cause of the extinction to be badly affected -- whether this was an asteroid impact in the Gulf of Mexico, where a giant buried impact crater is found today, or extreme volcanism in the Deccan volcanic province in India. Furthermore, it had been proposed that animals and plants in the polar regions would have been more resilient to global climatic changes associated with an asteroid impact as a result of living in environments that were always strongly seasonal. For example, life near the Poles has to adapt to living in darkness for half of the year and to an irregular food supply.

大滅絕事件的成因可能為小行星撞擊墨西哥灣，深埋於此的撞擊坑直到今日才被發現；另一個可能則是發生於印度德干火成岩省的超級火山噴發事件。不管為何者，先前科學家認為生活在極區的生物離這些災難夠遠，因此所受的影響不會那麼嚴重。此外，也有研究提出棲息在極區的動植物因為生活環境季節變化十分激烈，比方說半年的黑夜生活以及糧食供應不規則，因此能夠適應於此的生物比較能抵抗小行星撞擊引發的全球氣候變遷。

Professor Jane Francis from the British Antarctic Survey, a co-author of the study, said: "These Antarctic rocks contain a truly exceptional assemblage of fossils that have yielded new and surprising information about the evolution of life 66 million years ago. Even the animals that lived at the ends of the Earth close to the South Pole were not safe from the devastating effects of the mass extinction at the end of the Cretaceous Period."

英國南極調查所的共同作者Jane Francis教授說：「這些南極岩石中的化石組成真的相當特殊，我們從中獲得了6600萬年前令人驚訝的生物演化新資訊。在白堊紀末期，即便是生活在地球邊境，靠近南極的動物依然無法從大滅絕造成的毀滅效應中安全脫身。」

While some previous studies have suggested that the demise of the dinosaurs and other groups was gradual, many scientists argue that the dinosaur fossil record in particular is patchy, and cannot compete with marine fossils in terms of quantity and biodiversity.

雖然部分前人研究中認為恐龍以及其他種類的生物滅亡過程是漸進式的，許多科學家卻爭論說恐龍的化石紀錄特別零散，不論是生物多樣性以及保存品質都難以跟海洋生物化石相提並論。

James Witts said: "Most fossils are formed in marine environments, where it is easy for sediment to accumulate rapidly and bury parts of animals, such as bones, or bodies of creatures with a hard shell. For a dinosaur or other land animal to become fossilised, a series of favourable events are needed, such as for bones to fall into stagnant water and be buried rapidly to prevent decomposition, or be washed out to sea by rivers.

James Witts說：「大部分化石都形成在海洋環境當中。這是因為海洋中的沉積物很容易便迅速累積而埋藏生物遺骸的一部分，比方說骨頭或是有硬殼的部位。對於恐龍或是其他陸生生物而言，要成為化石必須發生一連串的有利事件，像是骨骸必須要落入缺氧水體中，接著被迅速埋藏而免於分解，或是被河水沖入海洋當中。」

"This means that marine fossils are generally much more abundant. They can give us a much larger data set for studying how ecosystems and biodiversity change over time in the geological past, and enable us to draw robust conclusions about events during periods of rapid environmental change, like mass extinctions."

「這代表海洋生物的化石數量一般來說是比較豐富的。它們可以給出更多資訊讓我們研究在地質史的過去，生態系和生物多樣性是如何隨著時間變化，而對像大滅絕之類的急遽環境變化期間發生了何種事件，我們也能依此得出更加穩健的結論。」

引用自：University of Leeds. "Antarctic fossils reveal creatures weren't safer in the south during dinosaur extinction." ScienceDaily. ScienceDaily, 26 May 2016.