The most ancient mammalian remains found so far date back to the upper Triassic period, 220 milion years ago. During the Jurassic and Cretaceous periods mammals, which were as small as modern mice, represented a small portion of terrestrial animals in a world dominated by reptiles and, in particular, dinosaurs. At the end of the Mesozoic era big changes on earth brought about the gradual exinction of dinosaurs while during the following era, the Cenozoic, Angiospermae (flowering plants) birds and mammals flourished. Complete fossils of Mesozoic mammals are very rare. Liaoning lake deposits have so far produced a few complete skeletons on detritic limestone slabs. Due to the difficulties in obtaining these rare fossils computer aided three dimensional copies have been made.