REMARKABLE SPATIAL DISTRIBUTION OF ORGANISMS IN THE LUOPING BIOTA (MIDDLE TRIASSIC), YUNNAN PROVINCE, CHINA

The fauna of the Luoping Biota, exposed in quarries near Luoping, Yunnan Province, China, consists of a broad spectrum of invertebrate and vertebrate organisms, of which the numerically most abundant are arthropods. The unit is early Middle Triassic (Anisian) in age and exhibits a major, remarkably diverse recovery fauna following the end-Permian extinction event. The fauna has recently been cast in a trophic web in which the arthropods, including decapods, thylacocephalans, isopods, myriapods, horseshoe crabs, and mysidaceans, have been interpreted as low level predators, scavengers, and pelagic food resources for fish and swimming reptiles. However, the distribution of the organisms is unusual, so that although the summary interpretation of interactions is undoubtedly correct, additional interpretation is required. Detailed mapping of five surfaces in two quarries documented what are interpreted as mass kills of pelagic arthropods, including shrimp, thylacocephalans, and mysidaceans. The mapped surfaces were overwhelmingly dominated by single pelagic arthropod taxa. Subsequent mapping of 10 surfaces in a third quarry demonstrated the same pattern of a single dominant taxon on each surface; however, in Quarry 3 some of the surfaces were dominated by benthic organisms, such as lingulid brachiopods, crinoids, and small bivalves. The segregation of benthic taxa on different levels within Quarry 3 requires a special interpretation and brings into question whether the entire Luoping assemblage did, in fact, interact. The work was supported by grants from the National Science Foundation, National Geographic Society, and the Chinese Geological Survey.