A major drop-off in ocean levels push many crocodile ancestors to extinction around 145 million eld ago at the boundary between the Jurassic and Cretaceous period , agree to novel findings bring out inProceedings of the Royal Society B. And this massive decline was a blessing for former marine turtle .
Crocodyliforms used to be tremendously diverse , and they have a much robust evolutionary history than you ’d expect try from their living descendants , which include today ’s alligators and crocodiles . Some swam in the ocean and turn up to 12 meters recollective ( 39 substructure long ) , while others were much smaller and lived on land . base on fossil , research worker have known about the defunctness event at the Jurassic / Cretaceous ( J / K ) boundary for decades , but the personal effects of crocodyliform declension remained largely unstudied .
So , a trio of researchers run byJonathan Tennantof Imperial College London reverse to a digital archive call the Paleobiology Database to look for change in longer - term trends in crocodyliform fogey records span 201 million to 66 million long time ago .
They find a huge biodiversity crash across the J / K boundary : More than 75 percent of genus live on estate and at ocean were lose . While non - marine biodiversity part recovered , maritime biodiversity remained low throughout the former Cretaceous . The remain crocodyliform species diversified into new groups such as the now - out notosuchians , which were about 1.5 meter long ( 5 foot long ) . The eusuchians arrive to prominence after the extinction effect , and they contribute up to today ’s crocodile .
This monolithic decline was mostly because of a drop in sea grade , which closed off shallow maritime environments like the lagoons and coastal swamps where many crocodyliforms live and hunt . to boot , a change in ocean water interpersonal chemistry also increase sulfur perniciousness and depleted oxygen .
Furthermore , the team found that the timing of the mass crocodyliform extinction coincided with the origin of modern marine turtles . Their ascendent were common prey for ancient nautical crocs . " This major extinction of crocodyliforms was literally a guinea pig of out with the erstwhile and in with the Modern for many species , " Tennant says in astatement . " Marine turtles , the gentle , graceful creatures of the sea , may have been one of the major winners from this changing of the old guard . They begin to thrive in sea around the world when their furious archway - predators went into last decline . "
However , the free fall in nautical croc diversity also pave the way for their ecological replacement , include sharks , plesiosaur , and other large predators .
