The biota includes many species that were previously known only from the Upper Jurassic or earlier. These include the dinosaur "Sinosauropteryx", and the pterosaur "Dendrorhynchoides". There was even a primitive protomammal – a tritylodont therapsid – from Lower Cretaceous Japan. Tritylodonts were previously thought to have gone extinct in the Middle Jurassic. The biota also has the earliest and most basal (primitive) known members of groups which spread all around the world by the Upper Cretaceous, including neoceratopsians, therizinosaurs, tyrannosaurs, and oviraptors.