The discovery of a gigantic marine reptile that hunted in the oceans near what is now southwestern China during the Middle Triassic (around 237-247 million years ago) indicates that marine ecosystems across the world at this time were rich enough to support such apex predators. The fossil remains belong to a creature named Nothosaurus zhangi, described in Scientific Reports this week, which possesses the largest known lower jaw among a group of Triassic aquatic reptiles called sauropterygians.
Around 252 million years ago a mass extinction event took place that wiped out nearly all life on Earth. Evidence for the appearance of large apex predators by the early Middle Triassic period, which indicate re-establishment of marine diversity, has been reported for a few regions of the ancient oceans, but not for the region surrounding ancient southern China. Thus, it has been unclear whether the recovery of marine ecosystems took place synchronously on a global scale.
The new fossil nothosaur unearthed by Jun Liu and colleagues, from an early Middle Triassic formation in southwestern China, seems to fill this gap and indicates that stable and complex food webs in the oceans had been established globally by this time. Nothosaurus zhangi had a very large jaw (65 cm long), fang-like teeth, and an estimated body length of 5-7 metres. The size of its skull and presence of large, sharp teeth suggest that this creature was at the top of the food web, and the authors propose that this creature may have attacked prey, such as large fish and other marine reptiles.