Monster Nothosaur from China Suggests Ecosystem Recovery after Mass Extinction Event

A team of Chinese scientists, supported by palaeontologists from Bristol University, Washington D.C. and Australia, writing in the academic journal “Nature: Scientific Reports”, have described the fossilised remains of a giant marine reptile.  This fearsome hunter provides evidence that by around 245 million years ago, much of the world’s marine habitats had recovered sufficiently from the Permian/Triassic mass extinction event to support complex food chains.  The Permian/Triassic extinction event is often referred to as the “Great Dying”, a huge portion of life on Earth died out, scientists debate just how many different types of organisms perished, but it has been suggested that as much as 95% of all life on Earth became extinct.

To read more about how mass extinction events are defined: When is an Extinction Event a Mass Extinction?

The fossil represent a new species of Nothosaur, it is potentially the largest Nothosaur discovered to date.  The discovery is significant as it indicates that on the eastern side of the Paleotethys Sea, marine life had recovered sufficiently to support complex food chains, with carnivorous marine reptiles as the apex predators in the environment.  As similar sized apex predators are known from the western fringes of the Paleotethys Sea and also from the eastern seaboard of the Panthalassa Ocean, this provides evidence to support the theory that by the early part of the Middle Triassic there had been a global recovery (a synchronous global recovery), of marine fauna and flora.

The Nothosaur fossil consisting of an almost complete lower jaw, isolated teeth and post cranial elements was discovered in 2008.  The only known specimen was collected from Bed number 165 of the Dawazi section of strata, a highly fossiliferous zone that represents a shallow marine environment.  The fossils are located in Luoping County, Yunnan Province in the far south-west of China.  This part of the world is famous for its Middle Triassic marine fossils, many thousands of specimens have been collected including a number of Ichthyosaurs as well as other marine reptiles.

The Nothosaur Fossil Material (a) Line Drawing (b)

The specimen has been named Nothosaurus zhangi

The specimen has been named Nothosaurus zhangi

Picture Credit: Nature: Scientific Reports

Nothosaurs were a group of marine reptiles related to the better known Plesiosaurs.  They evolved from terrestrial ancestors and typically were between one and three metres in length.  They had relatively long snouts, quite narrow skulls, and their fingers and toes may have been webbed to help propel them through water.  The were also capable of hauling themselves up onto land and although well adapted to a marine environment, they probably rested and bred on land.  The Nothosaurs evolved very early on in the Triassic Period and as a group they persisted up until the beginning of the Jurassic.

 A Model of a Typical Nothosaur (Safari Prehistoric Sealife Toob)

One of the models in the Safari Prehistoric Sealife Toob.

One of the models in the Safari Prehistoric Sealife Toob.

Picture Credit: Everything Dinosaur

The picture above shows a typical Nothosaur bauplan (body plan), it is one of the models from the fantastic “Prehistoric Sealife Toob”, part of the range of prehistoric animal and plant replicas made by Safari Ltd.

To view this range: Safari Ltd Prehistoric Replicas

This new giant species of Nothosaur has been named Nothosaurus zhangi.  The species or trivial name honours the discoverer of the Luoping biota, scientist Qiyue Zhang.  Although far from complete, a comparative analysis using fossil material from the Nothosaur species known as N. giganteus, whose fossils come from Middle and Upper Triassic aged rocks in Germany, suggests that Nothosaurus zhangi was between five and seven metres in length.  Think of this ancient reptile being about the size of a large Nile crocodile (Crocodylus niloticus).

The jaw was lined with a number of sharp, pointed teeth, many of which projected outwards to give the impression of elongated fangs.  These were adaptations to grabbing and subduing struggling prey, such as fish and cephalopods.  Given the size of Nothosaurus zhangi, it very probably hunted other, smaller marine reptiles in the shallow, tropical sea that once covered much of China.

These fossils from what would have been the eastern side of the Paleotethys Sea, when considered with the fossilised remains of other enormous Middle Triassic marine reptiles, suggests that across the world marine environments had recovered sufficiently to support complex food chains by around 245 million years ago.

A Map of the Middle Triassic Showing the Location of Apex Predator Marine Fossil Finds

Marking the location of apex predator fossils.

Marking the location of apex predator fossils.

Picture Credit: Nature: Scientific Reports with additional material from the Palaeobiology database

The map shows a whole world projection of the Middle Triassic. The super continent of Pangea is firmly established and the locations of potential apex predator marine reptile fossils have been marked.

Key

  • Thalattoarchon O – (T. saurophagis) a giant Ichthyosaur estimated to have measured 8-9 metres in length (YELLOW)
  • Cymbospondylus (several species), a basal Ichthyosaur estimated to have reached lengths in excess of 10 metres (BLUE)
  • Nothosaurus giganteus – estimated to be about 5-7 metres long (PURPLE)
  • Nothosaurus zhangi – estimated to be about 5-7 metres long (RED)

Thanks to the astonishing variety of fossils from the Luoping Province, scientists have been able to build up a great deal of knowledge about life in the seas surrounding the ancient land mass on the western fringes of Pangea, that was to eventually become China. The researchers have been able to develop a complex food chain diagram and the newly described Nothosaurus zhangi is placed at the top of the food chain as the largest predator discovered to date.

A Food Chain Constructed Using Luoping Biota Fossil Data

Nothosaurus zhangi at the top of the food chain.

Nothosaurus zhangi at the top of the food chain.

Picture Credit: Nature: Scientific Reports

It may have taken terrestrial life slightly longer to recover from the end Permian extinction event, but based on this evidence, many of the shallow sea environments had recovered fully and new types of fauna had filled ecological niches.

To read an article published in April 2014 about the discovery of a bizarre type of marine reptile (Atopodentatus) from the Luoping Biota: Bizarre Triassic Marine Reptile Described

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