Claw of the Sphinx — A.J. Hunter

Beware the claws of the sphinx...
Geology-mad Sam and her American cousin Trey are the Chosen Ones, destined to save the world from destruction by gathering together the scattered fragments of The Warrior's Shield. They've already rescued one section of the enchanted shield from the terrifying Medusa, and now learn that the second piece is being guarded by a fearsome sphinx - a creature with the body of a lion, the wings of an eagle and the face of a human. So Sam and Trey must travel to Ancient Egypt, and face mummies, beast-headed warriors... and the deadly sphinx itself!