Can't confirm or deny, but I don't think so. Apart from that making four evo's in a line (as opposed to ones that have a choice of 3rd stages), it's listed as being a different water egg group to the Horsea line - and *all* pre-evos are in the "no eggs" group.
As far as I can tell, there was some early speculation that it was a pre-evo, because of its position in the pokédex and because it looks unevolved.
rinku