Robert Temple has a theory what did the sphinx look like in the past:
[link to fotolog.terra.com.mx]
[link to fotolog.terra.com.mx]
We know the head we see now is too small compared with its body and all other sphinxes in Egypt. Geologist Robert Schoch believes it was a woman with long jaw like the ones in Congo; Egyptologist Anthony West believes it belonged to a lion or perhaps half lion-half man (I'm incline to think that because the link with Mars' Face). The sphinx used to have a beard as we see in the museum:
[link to fotolog.terra.com.mx]
And though the body is certainly of the lion and not a dog's body. The paws are the ones of a feline. The tail could've been lion or even bull's in the past.