I saw a block of text recently suggesting that the Sphinx may have originally been a representation of Anubis, recarved over the years as erosion took its toll. It seems this theory was brought forward in a book by Robert Temple, The Sphinx Mystery: The Forgotten Origins of the Sanctuary of Anubis. Temple seems to be a bit of a fringe conspiracy type, but this is one of those theories that just seems to make sense, given how prevalent the jackal is throughout Egyptian art. Do historians take this possibility at all seriously?
I think characterizing Robert Temple as a "bit of a fringe conspiracy type" is being overly generous. He's a full-on "ancient aliens" conspiracy type, with absolutely no academic standing. My advice is to dismiss pretty much everything that he puts forward as his own original research.
As far as the Sphinx/Anubis thing goes, you could superimpose pretty much any figure over the Sphinx and claim it has eroded over the years, but unless there is some sort of written or archaeological record, there is no reason to take the claim seriously. Lion/eagle/bull/man hybrids were pretty popular in the Ancient Near East, so there isn't really any reason to think that the Sphinx is out of place.
