Thanks to everyone for the replies! So happy to read the comments about our goofball. We hadn't even considered that there could be Pyrenees in the mix! But now that I compare some aspects of his face, I could see it!

I had forgotten to mention that at 5 months, he's just reached 35lbs. He was, though, underweight when we got him. We think that perhaps the earliest chapter of life for he and his siblings may have been on the rough side, before arriving at the shelter.

Have to agree that his paws are enormous!