I guess ultimately the most convincing opinion(s) brought out here, for me anyway, would be the engravers' basic unfamiliarity with the animals being depicted. The only red herring in this reasoning is that, as Franc mentioned, dogs and birds were quite familiar, and yet they got the same treatment.
As to pinning it down to a time period, that's up for grabs. Ditto for when the engraving style changed to more realistic depictions.
More could be discussed, but I'm afraid the only result would be an acceleration of the merry-go-round.
Many thanks to all who weighed in on this topic. To me, it's just one more fascinating, intriguing aspect of these beautiful old guns we find so entrancing. I'm sure glad they're still around!
