When I 1st saw them I thought they looked like a mixture of a bear + owl, so owlbear:

Bears are also naturally chubby.

Which we later find out that Owlbears are (one of the) 1st chimerical creations of the Allagan:


We know that the Vanu Vanu were tasked with protecting the Key to Azys Lla, but most importantly we know that Ixalion evolved into Ixal, so it may be possible that Owlbears evolved into the Vanu Vanu


In other words, they might be Allagan chimerical creation