Simplify the following text for a Grade 15 native English-speaking person.
Original: Although almost every therocephalian lineage ended during the great Permianâ `` Triassic extinction event , a few representatives of the subgroup ( called Eutherocephalia ) survived into the early Triassic and continued to diversify .
Simplified: Although almost every therocephalian lineage ended during the great Permianâ `` Triassic extinction event , a few representatives of the subgroup called Eutherocephalia survived into the Early Triassic .