Out Of Time by Emily Holland
“There…!” S’rebren cried, leaning hard right over Krodith’s neck, and then sat back as his eyes resolved only a boulder, rearing from the ground, matted vegetation drooping, wing-like, from its sides.
Then, No, Krodith said, there!
She wheeled hard left, putting on a spurt of speed, her slender muzzle pointing the way. S’rebren thought for an instant that even his dragon was mistaken, but then a heap of rocks stirred and moved and raised its head: dark, with eyes glowing eerie white.
“Hey, down there!” S’rebren shouted as Krodith circled in to land. “You all right?”
The dragon below curved his head threateningly towards Krodith with a hiss. (Prologue, Dragonchoice 3)
Illustration from the prologue of Dragonchoice 3 – it was a few chapters before anyone figured out who the lost dragonpair here actually was!