Gideon Mantell. Engraving of Gideon Algernon Mantell (1790-1852), British geologist. Mantell studied medicine in London but developed an obsessive interest in geology, and particularly in paleontology. His fossil-filled house in Brighton became a popular public museum before he sold his collection to the British Museum in 1838. In 1822 Mantell and his wife first discovered the remains of a dinosaur at Tilgate Forest in the Cretaceous rocks of the English Weald. It was a large herbivorous reptile and was named Iguanodon by Mantell because its teeth resembled those of the modern iguana lizard. In 1831 Mantell introduced the concept of an 'Age of Reptiles'.