A pair of astraspis searching for food
Astraspis is a genus of agnathan (jawless fish) that lived during the mid to late Ordovician. It is only about 20 cm long and lived in central North America (Central Laurentia?) and Bolivia, which the latter was part of Gondwana during the Ordovician. The main reason why the genus is called what it is because of the generally star-shaped tubercules on its body, giving it the name Astraspis, literally meaning star shield.
Death rays[]
Initially, a group of Astraspis is seen searching for food. When the gamma ray burst hits, they manage to hide away from the radiation to prevent being irradiated and cooked alive. Later on, it is shown that they were able to survive the extinction, and eventually evolve into new kinds of fish, including jawed fish, or gnathostomes.