The so-called marine strata refer to the strata formed by marine environments and their sediments in ancient times. Therefore, the fossils preserved in such strata are mainly marine organisms, such as sea lilies, starfish, ammonites and other invertebrates, as well as fish and marine reptiles. However, in the Triassic marine limestone of Yunnan and Guizhou, not only are there a large number of such marine fossils, but there are also a considerable number of terrestrial reptile fossils, such as the original dragon-like Hesperonychus, which resembled a lizard and could even "run" with its powerful hind legs when moving quickly, and the early mainosaurs, which looked like small crocodiles. This is a very rare phenomenon worldwide.
Studies show that these terrestrial reptile fossils are very complete, indicating that the animals did not undergo long-distance "transportation" after their death, that is, their bodies were not carried to the sea by water currents from distant land areas. Scientists speculate that in such areas, there may have been some small islands, on which a certain number of terrestrial reptiles lived, which were the sources of terrestrial animal fossils in marine strata.