Galapagos Saddleback Tortoise

Most of the Galapagos Islands each had their own distinct species of endemic giant tortoise. In areas with plenty of rain and more ground vegetation, they have short necks and low wrapping domed shells. But in the dryer regions, where the tortoises feed from tall pricklypear cacti, they have high upward arched "saddleback" shells with long necks for reaching up to the vegetation. Through their isolation, each island subjected their animal inhabitants to unique constraints, causing their form to slowly shift based upon the necessity of their environment.