Thomas Henry Huxley ("Darwin's bulldog"), who was a comparative anatomist, made a study of this nearly 150 years ago. He compared the first fossil bird, "Archaeopteryx", with a small theropod dinosaur, "Compsognathus". They are two fossils from the same place and time: the Solnhofen limestone in Bavaria, Germany. The strata come from the end of the Jurassic period, about 144 million years ago.