Research press release


Scientific Reports

Fossils: Large ancient fish is a prize catch


今回、Min Zhu、Brian Chooたちは、中国雲南省のシルル紀後期の堆積層から発掘された化石をもとにして、この新しい魚について記述している。この化石魚は、顎の長さが17センチと推定され、鋭くないが強靭な歯を持ち、殻の硬い獲物を食べるのに適していたという見方を論文著者は示している。こうした特徴は、この魚に付けられた名称であるMegamastax amblyodusに反映されている。これは、「大きな口と鋭くない歯」という意味のギリシャ語に由来している。


Fossils of a fish that lived around 423 million years ago, described in Scientific Reports this week, provide new insights about the ancient creatures present at that point in history. With an estimated length of roughly 1 metre, the new form is far larger than any other vertebrate (backboned animal) known from that time. Previously, the apparent lack of large fishes in rocks over 380 million years in age was thought to indicate a restricted growth limit due to lower oxygen levels, but the new finding refutes that assumption.

Min Zhu, Brian Choo, and colleagues describe the new fish, based on fossils discovered in late Silurian sediments in Yunnan, China. The creature has an estimated jaw length of 17 cm with blunt, strong teeth, ideal for eating hard-shelled prey, the authors suggest. These features are reflected in the name assigned to this fish: Megamastax amblyodus, derived from Greek words meaning “big mouth, blunt tooth”.

The Devonian period (around 358-419 million years ago) has been considered to mark a major transition in the size and diversity of early jawed vertebrates, including the earliest appearance of large predatory fishes. Until recently the largest jawed vertebrates in the preceding Silurian period were roughly 35 cm in length. The discovery of a metre-long, predatory Silurian fish provides evidence that pre-Devonian creatures could attain comparatively large sizes.

doi: 10.1038/srep05242

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