Complex sentence: While the early tetrapods flourished and quickly diversified over the next 30 million years, the elpistostegalians disappear from the fossil record fairly quickly in the early Frasnean around 380 million years ago, leaving the labyrinthodonts the sole survivors of their line.
Split into simpler sentences: While the early tetrapods flourished and quickly diversified over the next 30 million years. They disappear from the fossil record fairly quickly in the early Frasnean around 380 million years ago, leaving the labyrinthodonts the sole survivors of their line.