The sea horse head : PEOPLE have bred that in
Tabletop croup(not back): put any Arabian in that artificial show pose, under tension, you get that croup.
Show me these pictured horses standing square, normal, and lets judge then.
And, for the horse with the sea horse head...I bet, without make up, out on pasture and a little less "editing", he's only half sea horse.
I have seen quite a few show horses at home, behind closed doors, so to speak, and I didn't recognize a single one.
Oh, and btw....