범고래 크기의 두 배 거대한 플리오사우루스가 쥬라기 후기 바다를 헤엄쳤다는 새로운 증거

플리오사우루스에 대한 화가의 인상. 크레딧: Megan Jacobs, 포츠머스 대학교

20여 년 전에 그는 25미터 길이로 사진을 찍었습니다. 리오플레우로돈 BBC 다큐멘터리 시리즈인 Walking with Dinosaurs에서 이 플리오사우르스의 실제 크기에 대한 열띤 논쟁이 벌어졌습니다. 묘사는 일반적으로 과도하게 과장된 것으로 간주되었으며 가장 널리 받아들여지는 이론은 성체 리오플레우로돈의 크기가 6미터가 조금 넘는다는 것입니다.

그러나 그러한 추측은 계속될 것으로 예상되었으며, 이제 옥스퍼드셔 박물관에서 발견된 우연한 발견으로 인해 포츠머스 대학의 고생물학자들은 유사한 발견이[{” attribute=””>species could reach a staggering length of 14.4 meters, twice the size of a killer whale.

Professor David Martill from the University of Portsmouth’s School of the Environment, Geography and Geosciences, said: “I was a consultant for the BBC’s pilot program‘ Cruel Sea’ and I hold my hands up – I got the size of Liopleurodon horrendously wrong. I based my calculations on some fragmentary material that suggested a Liopleurodon could grow to a length of 25 meters, but the evidence was scant and it caused a lot of controversy at the time.

“The size estimate on the BBC back in 1999 was overdone, but now we have some evidence that is much more reliable after a serendipitous discovery of four enormous vertebrates.”

Professor Martill’s co-author, Megan Jacobs, was photographing an ichthyosaur skeleton at Abingdon County Hall Museum, while Dave looked through drawers of fossils. He found a large vertebra and was thrilled to discover the curator had three more of them in storage.

The vertebrae are clearly identifiable as being closely related to a Pliosaurus species or similar animal. Pliosaurs were like plesiosaurs, but with a bigger elongated head, similar to a crocodile, and a shorter neck. They had four flippers, which acted as powerful paddles to propel them through water, and a relatively short tail.

After conducting topographic scans, Professor Martill and colleagues calculated this Late Jurassic marine reptile could have grown to between 9.8 and 14.4 meters long.

He said: “We know these pliosaurs were very fearsome animals swimming in the seas that covered Oxfordshire 145-152 million years ago. They had a massive skull with huge protruding teeth like daggers – as big, if not bigger than a T. rex, and certainly more powerful.

“They were at the top of the marine food chain and probably preyed on ichthyosaurs, long-necked plesiosaurs, and maybe even smaller marine crocodiles, simply by biting them in half and taking chunks off them. We know they were massacring smaller marine reptiles because you can see bite marks in ichthyosaur bones in examples on display in The Etches Collection in Dorset.”

The vertebrae were originally discovered during temporary excavations at Warren Farm in the River Thames Valley in Oxfordshire and come from the Kimmeridge Clay Formation. This deposit is Late Jurassic in age, around 152 million years old.

Professor Martill added: “It’s wonderful to prove there was indeed a truly gigantic pliosaur species in the Late Jurassic seas. Although not yet on a par with the claims made for Liopleurodon in the iconic BBC TV series Walking With Dinosaurs, it wouldn’t surprise me if one day we find some clear evidence that this monstrous species was even bigger.”

Reference: “A truly gigantic pliosaur (Reptilia, Sauropterygia) from the Kimmeridge Clay Formation (Upper Jurassic, Kimmeridgian) of England” by David M. Martill, Megan L. Jacobs and Roy E. Smith, 10 May 2023, Proceedings of the Geologists’ Association.
DOI: 10.1016/j.pgeola.2023.04.005