User blog comment:Lord Loss/Monster Hunter Theory... Blog/@comment-2248808-20110826032448/@comment-4256715-20110829110644

well there wasn't said either that they are a subspecies from rathian. and i still believe that they are the elder rathian because otherwise the name would be just..not fitting i think. they could've called it redspiked rathian or sth. The other idea is that ancient rathian is just like a fossil..someone said that before..they've been asleep or just in hiding for ages (as it is quite common for dragons/wyverns in mythology) and just got up now. while other rathian lived on and obviously degenerated in terms of strength over the generations. maybe due to less competition with other monsters. who knows what kind of fierce monsters there were before the ancients went into hiding/sleep. that is obviously quite farfetched but it would explain the term ancient.