[SunkenCiv]

The term "sphinx" is a transliteration of the Egyptian (Old Coptic) term meaning "living image", so could easily refer to any statue. The Anubis idea is often put forward, also a more conventional lion. Clearly, the head has been recarved, since even those who won't accept the water erosion evidence are faced with the much worse erosion on the body compared with the head, which has been exposed to the elements while the rest of the statue has been covered with sand for most of the thousands of years since it was built. This is Colin Reader's take on it:

[PIF]

Except the body design most certainly does not resemble a lion’s in the slightest. So while putting a lion head on a body (as in the illustration) may satisfy certain assumptions, it does not change the plain facts, to wit the body is not that of a lion.

As for the name - ‘sphinx’ is not the name the Egyptians used for that object. I’d have to wade through a thick book to find the actual name, and it is too early by half in the morning. However, the hieroglyph referred to Anubis; sorry I cannot recall it off hand at the moment - perhaps later after I make some coffee.

The general body shape is not eroded, just the details show degradation.