Living oysters of Crassostrea Sp. are abundantly found on the east coast of peninsular India. Most of the living Crassostrea Sp. is reported from Athinkarai estuary near Mandapam. The primary object of this study is to report the occurrence of fossils of Crassostrea sp. belonging to Mio-Pliocene outcrops from an ephemeral stream channel of Thoppuvila River up to Attankarai Pallivasal, Tirunelveli dist., Tamil Nadu, India. The present study focuses on revealing the nature of a vast paleo estuary that existed on the foothills of the southern end of the Western Ghats during the Mio-Pliocene age. The authors had studied the taphonomical features of Crassostrea Gigantissima Sp. Focusing on the adaptation features like heaviness and foliated nature of shell and orientation of oyster colonies for survival. The predatory signatures on the fossil specimens indicate traces of a well flourished marine environment that resembled an estuary subjected to high energy disturbances. The chalky calcareous deposits found throughout the study area could have acted as an accelerating agent for the thick, foliated and heavy calcite shells of C. Gigantissima Sp.