question: How many years is the Hirnantian faunal stage believed to have lasted ?
answer: 0.5 to 1.5 million years
turker_answer: The Hirnantian faunal stage is believed to have lasted 0.5 to 1.5 million years .
rule-based: The Hirnantian faunal stage believed to have lasted is 0.5 to 1.5 million years .