Hacker News Reader

What does MYa mean?

I thought it meant million years ago,but he writes "400MYa ago" and "200Mya [...] from now"

Megayears ago. It is a million years.. . http://en.wiktionary.org/wiki/megayear

Maybe he meant "MYa" to mean megayears? I'm guessing this because he also used "GYa", which could be gigayears.