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Mesozoic |
1 Department of Paleobiology, NHB-121, National Museum of Natural History, Washington, DC 20560, USA
2 Nanjing Institute of Geology and Palaeontology, Academia Sinica, Nanjing, People’s Republic of China
The biotic recovery following the end-Permian mass extinction begins with a long lag phase characterized by a low-provinciality, depauperate biota. Normal marine communities do not reappear until the latest Early Triassic (Spathian) and do not become common until the early Middle Triassic (Anisian). Three explanations have been offered for this pattern: first, that the end-Permian extinction so disrupted marine ecosystems that community assembly rules needed to be rewritten prior to the re-establishment of normal community structures; second, that the recovery was delayed by continuing harsh environmental conditions; and third, that the preservational and sampling bias is significant and the pattern more apparent than real.
Data on the stratigraphic, biogeographical and environmental distribution of Wordian-Anisian marine gastropod genera and species were used to evaluate these hypotheses. The results demonstrate (1) an initial removal of endemic (narrowly distributed) genera during the Wordian and Capitanian; (2) the presence of a low provinciality gastropod assemblage during the Djulfian and Changxingian; and (3) the persistence into the earliest Triassic of geographically widespread, environmentally tolerant genera, as well as the apparent (but unobserved), occurrence of numerous ‘Lazarus’ taxa. The data indicate that while preservational bias was significant, environmental dampening was also important.
