Ancient Zoan

As stated by Scratchmen Apoo, the Ancient Zoan (「動物系」古代種, Zon-kei Kodaishu) is apparently a much rarer type of Zoan Devil Fruit which allows the users to transform into ancient and extinct animals, such as prehistoric reptiles like the dinosaurs. The only Ancient Zoan that has been shown so far is wielded by X. Drake, allowing him to transform into a carnivorous dinosaur, the tyrannosaur.