 The Triassic @-@ Jurassic extinction event around 199 @.@ 6 Mya led to the extinction of most Mesozoic temnospondyls . The brachyopoids survived , as well as a few capitosauroids and trematosauroids . While the latter two groups soon became extinct , brachyopoids persisted and grew to large sizes during the Jurassic . Among brachyopoids , the brachyopids flourished in China and the chigutisaurids became common in Gondwana . The most recent known temnospondyl was the giant chigutisaurid Koolasuchus , known from the Early Cretaceous of Australia . It survived in rift valleys that were too cold in the winter for crocodiles that normally would have competed with them . Koolasuchus was one of the largest of the brachyopoids , with an estimated weight of 500 kg ( 1 @,@ 100 lb ) . 
 The Triassic @-@ Jurassic extinction event around 199 @.@ 6 Mya led to the extinction of most Mesozoic temnospondyls . The brachyopoids survived , as well as a few capitosauroids and trematosauroids . While the latter two groups soon became extinct , brachyopoids persisted and grew to large sizes during the Jurassic . Among brachyopoids , the brachyopids flourished in China and the chigutisaurids became common in Gondwana . The most recent known temnospondyl was the giant chigutisaurid Koolasuchus , known from the Early Cretaceous of Australia . It survived in rift valleys <a href='null_relcl' title='1'><mark>that</mark></a><a href='uninflect' title='2'><mark>were</mark></a> too cold in the winter for crocodiles <a href='null_relcl' title='3'><mark>that</mark></a>normally would <a href='been_done' title='4'><mark>have</mark></a> competed with them . Koolasuchus was one of the largest of the brachyopoids , with an estimated weight of 500 kg ( 1 @,@ 100 lb ) . 
Da Triassic @-@ Jurassic extinction event around 199 @.@ 6 Mya led to the extinction of most Mesozoic temnospondyls . The brachyopoids survived , as well as a few capitosauroids and trematosauroids . While the latter 2 groups soon became extinct , brachyopoids persisted and grew to large sizes durin the Jurassic . Among brachyopoids , tdabrachyopids flourished in China and the chigutisaurids became common in Gondwana . Thdaost recent known temnospondyl was the bigass chigutisaurid Koolasuchus , known from the Early Cretaceous of Australia . It survived in rift valleys was too cold in thedanter for crocodiles normally would done competed with em . Koolasuchus was one of the dagest of the brachyopoids , with an estimated weight of 500 kg ( 1 @,@ 100 lb ) .