"Seapony" vs. "Mermare" Tags

A question on whether we should be making a distinction here or not:
 
Apparently according to the “Under the Sparkling Sea” book, there are two types of aquatic ponies–Seaponies and Mermares. Also, I’ve seen artists draw aquatic ponies in two styles. The first are like the Generation 1 Sea Ponies, with seahorse-like bodies. The second are like regular ponies with fish-tails. Should we be calling out the first type using the “Seapony” tag, and the second type using the “Mermare” tag?

Does anyone know what the difference is supposed to be? Do mermares actually look like the second example?
 
Unless the artist is specifically using the mermares from the book, I’d call them both sea ponies. People also draw the other pony types with different models, after all.