Thread:Dinoman972/@comment-25175729-20180617200843/@comment-47205-20180618083942

Whether or not families are defined on the basis of limb number has often been decided based on convenience. Typically, when limb count is merged it's when it's higher than the norm, so we have many families of tetrapods with more than four limbs (or non-wing limbs), because such creatures are rather rare and even more rarely do you get multiple creatures of a given sort with the same number of excess limbs.

As discussed on Discord, there often aren't objectively correct ways of deciding whether taxa should be merged or split, except in extreme examples such as splitting identically-defined taxa or merging utterly dissimilar ones. So there probably isn't a right answer as to whether amphitheres and wyverns should share a family (relatedly, perhaps you should discuss the pros/cons of using "wyrm" versus "amphithere").

Up to the creation of Amphitherae out of Dracodae seven weeks ago, they didn't. But then prior to the end of last July, Dracodae was what Amphitherae is now, being restricted to legless winged dragons. Although I was the one who made this redefinition, I would presently default to inaction and leave them split on the grounds that there's no dire need to merge them again, but if anybody really wants to do it differently then so be it.