Tui De Roy / Flightless Cormorant (Phalacrocorax harrisi) drying stunted wings at sunset, Punta Espinosa, Fernandina Island, Galapagos Islands, Ecuador

Mark Bowler / Hoatzin (Opisthocomus hoazin) chick in the hand, showing claws on wings. The claws are a vestigial feature which is lost by adulthood. Rio Yavari, Peru

Mark Bowler / Hoatzin (Opisthocomus hoazin) chick wing showing claw detail. The claws are a vestigial feature which is lost by adulthood. Rio Yavari, Peru (non-ex)

Mark Bowler / Hoatzin (Opisthocomus hoazin) chick climbing out of water using claws on wings. The claws are a vestigial feature which is lost by adulthood. Rio Yavari, Peru (non-ex)

Mark Bowler / Hoatzin (Opisthocomus hoazin) chick perched on branch showing claws on wings. The claws are a vestigial feature which is lost by adulthood. Rio Yavari, Peru (non-ex)

Mark Bowler / Hoatzin (Opisthocomus hoazin) chick in the hand, showing claw on the wing. The claws are a vestigial feature which is lost by adulthood. Rio Yavari, Peru

Ingo Arndt / Close up of pelvic spur of Malagasy tree boa (Sanzinia madagascariensis) the vestigial remains of the snake's legs. Endemic to Madagascar.

Doug Perrine / Whale shark (Rhincodon typus) with mouth open to feed; vestigial teeth visible in lower jaw. Photographer Deron Verbeck in background. Kona Coast, Hawaii, Hawaiian Islands. Central Pacific Ocean. Mode...

Pete Oxford / Flightless cormorant (Phalacrocorax / Nannopterum harrisi) drying its wings. Fernandina Is, Galapagos

Piotr Naskrecki / Vanzolini's Worm Lizard (Amphisbaena vanzolinii) legless without functional eyes live underground, Guyana

Flip de Nooyer / Hoatzin (Opisthocomus hoazin) close up of the vestigial claws on a chick's wing used for grasping, Guyana

Flip de Nooyer / Hoatzin (Opisthocomus hoazin) close up of the vestigial claws on a chick's wing used for grasping, Guyana