The earliest-known traces of Chelonians occur in the Permian rocks, in the lower portion, that is, of the New Red Sandstone of older geologists. These traces, however, are not wholly satisfactory, since they consist solely of the footprints of the animal upon the ripple-marked surfaces of the sandstone. Of this nature is the Chelichnus Duncani, described by Sir William Jardine in his classical work on the 'Ichnology' of Annandale in Dumfriesshire. The earliest unequivocal remains of Cheloniidae are in the Oolitic rocks (the Chelone planiceps of the Portland Stone).
Fossil Cheloniidae, Emydidae, and Trionycidae occur, also, from the Upper Oolites to the present day, the Eocene period being peculiarly rich in their remains. In the Tertiary deposits of India (Siwalik Hills) there occurs a gigantic fossil Tortoise - the Colossochelys Atlas - which is believed to have been eighteen to twenty feet in length, and to have possibly survived to within the human period.