Here's one more view of the same Mahisamardini and the very strange style Shiva from Ravalaphadi Cave, also at Aihole. As early as 6th century, Harle says.  
Dear SPS, Thanks for the great references on Devis. In '05 we visited the amazing Chaunsat Yogini Deul in Hirapur, Orissa and were given the names of all 64 by the caretaker; friend took photos of all the ones that still had faces. There were also 4 Rudras there in the centre, facing the 4 directions, one was an Ekapada -- quite a rare murthi. I've seen ones also at SriMukhalingam, Mahabalipuram and Madurai. Ekapadas found in TN might make an interesting 'blog' feature. Several more lists of the 64 Yoginis given in the H.C. Das book will be interesting to compare.
Sorry the 2 photos were missing. I meant to send them to VJ for his blog, and used the wrong address. Kathie