Q2016 specifies horns. Q2018 specifies a broader range of protuberances including antlers and perhaps teeth (tusks) as well.
That is a point of differentiation, but it is one of detail rather than substance. Whether the underlying mechanism is bone, tooth or hair, the desired result, getting humans to have hard bits sticking off, is identical.
The queries are so identical that everyone in responses and comments, including Q2016 OP are dancing around the issue of these protuberances only being on the humans' heads! Interesting, really.
Obviously, the standard practice is to VTC close Q2018 as a duplicate. A technical victory for Q2016, though the point is moot as neither query has been active in years.
I would suggest that the Mod Squod merge Q2018 into Q2016. I'd really like to see more merging of duplicate queries as I'd consider that the logical next step. As it stands, it seems that duplicates just get closed and are then abandoned. Sometimes they have good answers. Sometimes the duplicate is in and of itself a better question!
I've got the ball rolling by VTC Q2018 as duplicate and suggesting a merger.