User blog comment:Lord Loss/Monster Hunter Theory... Blog/@comment-6050823-20131219040951/@comment-5020152-20131231193051

^ Plesioth and its Piscene relatives could be wyverns that adapted to an aquatic environment, kind of like cetaceans in our world.

Also, Plesioth and Delex are related because they probably have some of the same genetic material. In taxonomy, that would mean that they are at least distantly related.