Powered By Ypfree!

上海性息_上海顶级夜网论坛

Posted by admin on 2019-08-15 in 上海性息 with No Comments


Prehistoric crocodiles survived a dinosaur-dominated world by running around like dogs, new research has found.

南宁桑拿

Unlike today’s crocodiles that mostly live in freshwater habitats and feed on mammals and fish, their ancient relatives were extremely diverse.

Some behaved like dogs and others adapted to life in the open ocean, imitating the feeding behaviour of today’s killer whales.

The research uncovers the hidden past of crocodiles – showing for the first time how the jaws of the fierce reptiles evolved, enabling them to survive in vastly different environments in a dinosaur-dominated world 235 to 65 million years ago.

The study was conducted by Tom Stubbs and Dr Emily Rayfield from the University of Bristol, together with Dr Stephanie Pierce from The Royal Veterinary College and Dr Phil Anderson from Duke University in the United States.

Mr Stubbs says the ancestors of today’s crocodiles have a fascinating history that is relatively unknown compared to their dinosaur counterparts.

“They were very different creatures to the ones we are familiar with today, much more diverse and, as this research shows, their ability to adapt was quite remarkable,” he said.

“Their evolution and anatomical variation during the Mesozoic Era was exceptional.

“They evolved lifestyles and feeding ecologies unlike anything seen today.”

The research team examined variation in the morphology (shape) and biomechanics (function) of the lower jaws in over 100 ancient crocodiles, using a unique combination of numerical methods.

Dr Pierce said they were curious how extinction events and adaptations to extreme environments during the Mesozoic – a period covering over 170 million years – impacted the feeding systems of ancient crocodiles.

“To do this we focused our efforts on the main food-processing bone, the lower jaw.”

By analysing variation in the lower jaw, the researchers provide novel insights into how the feeding systems of ancient crocodiles evolved as the group recovered from the devastating end-Triassic extinction event and subsequently responded to the distribution of ecological resources, such as habitat and foodstuff.

The research showed that, following the end-Triassic extinction, ancient crocodiles invaded the Jurassic seas and evolved jaws built primarily for hydrodynamic efficiency to capture agile prey, such as fish.

However, only a small range of elongate lower jaw shapes were suitable in Jurassic marine environments.

The study also revealed that variation peaked again in the Cretaceous, where ancient crocodiles evolved a great variety of lower jaw shapes as they adapted to a diverse range of feeding ecologies and terrestrial environments alongside the dinosaurs.

Surprisingly, the lower jaws of Cretaceous crocodiles did not have a great amount of biomechanical variation and, instead, the fossil record points towards novel adaptations in other areas of their anatomy, such as armadillo-like body armour.

“Our results show that the ability to exploit a variety of different food resources and habitats, by evolving many different jaw shapes, was crucial to recovering from the end-Triassic extinction and most likely contributed to the success of Mesozoic crocodiles living in the shadow of the dinosaurs,” Dr Pierce said.

This exceptional variation has never before been explored numerically, with no studies ever having incorporated such a wide range of crocodiles over such a long time period.

The findings are published in the journal Proceedings of the Royal Society B.

The research was partially funded by the Natural Environment Research Council and the Biotechnology and Biological Sciences Research Council.

« previous post

Venezuela beat Peru 3-2 to keep Wor...

南宁桑拿Peru fell out of the running as both teams, who met in the 2011 Copa America third-place playoff won by the Peruvians, needed a victory to stay in the hunt for a place in Brazil next year.Venezuela are in sixth place in the nine-nation South American group with 19 points and one match remaining, thr...

next post »

Exploring cross-cultural attitudes ....

南宁桑拿(Transcript from World News Australia Radio)While most people experience sleep difficulties at some time in their lives, scientists suspect refugees may have a much higher incidence of sleep disorders than other Australians.And while problems sleeping have been much studied from a medical perspectiv...

No trackbacks yet.

Posts with similar tags

No post with similar tags yet.

Posts in similar categories

About Me Sample Title

This is a sample text about you. You may login and go to the Finojaho settings page and edit this text. Here you can display a summary of your website or anything that is interesting to your visitors. You also can disable this section completely. You have full control thru the settings page.