There are two creatures situated below the angels and above the demon on the holy water font seen just inside the entrance to Sauniere's church, that seem to be the mythical Basilisks.

Holy Water Font from Sauniere's Mary Magdalene Church

The Two Basilisks

What is a Basilisk?

1 - Classical Mythology . a creature, variously described as a serpent, lizard, or dragon, said to kill by its breath or look.

2 - Any of several tropical American iguanid lizards of the genus Basiliscus, noted for their ability to run across the surface of water on their hind legs.

I imagine it is the 1st description that is to be given to Sauniere's creatures.

A frame taken from a video taken inside Sauniere's church, reveals that the heads were missing. Perhaps loose and to prevent them from being stolen, they were removed for safe keeping. They have now been glued in place.

Missing Basilisk Head

 

Are the Basilisk's unique to Sauniere's church?

Although their are slight differences, the Basilisks also appear in Bram church on the frames of the stations of the cross.

Station of the Cross 14 from Bram church showing similar Basilisks

Another interest to not on the above image is the round plaque with the station number on. It matches that on Sauniere's Holy water font.

What is unknown is if Sauniere utilised this design first and then it was later copied for the station of the cross frames, or vice versa.

Jesus and John Statue

Two Statues Matching Sauniere's

BEGINNINGS - Book 1 of the TOMB, the TEMPLE, the TREASURE

Secrets of Rennes-le-Chateau