Thank you Shankar and Ganesh.
And for others that are wondering:
it is the very delicate underside of a camel's foot. Looks like cracked rubber/leather, or a bald tire ... but is soft. And it grows sore walking on harsh, hard or poky surfaces - and slips on mud. Made for walking on sand.
found it intriguing when i caught sight of it, because, if you notice, when a camel sits, its soles are always tucked inside ... you never really see this, unless a camel is lying down.