"Something much worse than asteroids" is hype: the late-#Devonian and end-#Ordovician were less severe that the end-#Cretaceous, which was definitely† caused by an #asteroid. But this is good work that may help nail down the cause of the earlier #extinctions ... which were still pretty bad!

†Yes.

https://www.earth.com/news/at-least-two-of-earths-mass-extinctions-caused-by-massive-supernova-explosions/