Riding in Pellucidar is a fine art thanks to the thoat. A vicious creature that comes in two sizes, Green martian and red martian. The latter being the smaller of the two although no different in appearance.
How ever Artists seemed divided on the look of the mighty thoat. 8 legged and vicious as it is, its still ridden by almost everyone, so it has to be a bit horse like, although its smooth skin and heavy padded feet suggest a lizard like animal or a hairless dog.
I avoided drawing one for along time but here i pictured John Carter's escape with Deja Thoris astride a mighty green martian Thoat. Enjoy