A new fossil found in China has provided fresh information on how ocean life replenished and evolved following the mass extinction 250 million years ago.
Fossil provides evidence of faster evolutionary process in oceans
The fossil, discovered in the Majiashan Quarry, which is in Anhui Province, China, has been classified as an early ancestor of the ichthyosaurs, a reptile that populated seas in the time of the dinosaurs.
Following a mass extinction in the oceans around 250 million years ago (it is believed that over 95% of marine life was wiped out due to rising sea levels, huge volcanic eruptions and climate change), scientists have traditionally believed that the re-population process was a slow process. However, this newly classified fossil named Sclerocormus parviceps throws doubt over this theory.
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The fossil indicates that marine reptiles were quick to evolve following the cataclysmic events.
Working on the project, Dr Nick Fraser, Keeper of Natural Sciences at National Museums Scotland and teams from both the US and China released details of the find in Scientific Reports
“Here’s something that gives us a sense of the evolutionary pathway,” stated Dr Fraser.
“We’ve still got a long way to go to see where the ichthyosaurs came from, however it’s a step in the right direction. He also said “… it all points to a very rapid radiation after this mass extinction – this mother of all extinctions at the end of the Permian, which had a major impact on the Earth.”
Sclerocormus parviceps versus ichthyosaurs
The ichthyosaurs were an abundant marine species occupying the Jurassic and the Cretaceous periods. They were similar in shape to a dolphin with a sleek body and long protruding snouts. However, this new ancestor appears to have had a much shorter snout and thicker body due to a larger ribcage.
It is also thought that this older version lacked the teeth its more recent ancestors possessed; meaning food was probably sucked up rather then eaten and chewed.
“It looked a bit like a small-headed porpoise with a fairly broad stiff body,” Dr Fraser said when speaking to the BBC News.
Also involved in the project, Prof Ryosuke Montani of the Department of Earth Science at UC, said that “Sclerocormus is one of the most surprising marine reptiles that I have seen” and added “Measuring 1.6 meters in total length it was one of the largest marine vertebrates of the time.”
Filling The Gap
Scientists have long sought a ‘missing link’ between the specimens of primitive marine reptiles already discovered and ichthyosaurs which came later and were found in great numbers. This new fossil provides some light on what happened in the intervening years.
Co-researcher, Dr Olivier Rieppel of The Field Museum in Chicago commented, “We don’t have many marine reptile fossils from this period, so this specimen is important because it suggests that there’s diversity that hasn’t been uncovered yet.”
Rieppel added, “These ichthyosauriforms (ichythyosaurs and close relatives) seem to have evolved very quickly, in short bursts of lots of change, in leaps and bounds.”
This runs counter to what was previously understood.
China – A Great Fossil Resource
China has become a rich source of new fossil remains for various marine reptiles. The quarries, which are being extensively investigated, have unveiled other new finds before this Sclerocormus. Only early this month a marine reptile with strange hammer shaped skull was discovered, named Atopodentatus, which is thought to have lived some 240 million years ago.