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Earth & Life (http://www.geofinds.com), 2006-10-1, Vol.1. , No.1: 16-30
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Ecological selection in end-Permian mass extinction and its climatic implication* 1
Abstract Ecological selection in end-Permian extinctions of plants, reefs and reef-building thalamid sponges, foraminifers, bivalves, ammonoids, gastropods, brachiopods, ostracods and insects are analyzed and found that the extinct taxa are warm-water, stenobiontic organisms, while the sparse taxa that survived the crisis are eruytropic or eurythermal organisms that can inhabit cold water environments. Keywords: end-Permian, mass extinction, Permian-Triassic transition, selection, climate
1. Reefs and reefal organismsModern reefs are distributed in low latitude warm water, shallow seas. Paleozoic reefs are believed to have similar geographic distribution, as they have similar formation mechanism. Reefs in Late Permian Changhsingian have worldwide distribution. They have been reported from Greece, Thailand, and southern China (including Jiangsu, Jiangxi, Hunan, Hubei, Guizhou, Sichuan, Guangxi provinces). Many of them have large scale and typical structure such as crustose fibrous cements. All Changhsingian reefs disappeared at the latest Permian. As described by Flügel (1994), the Lower Triassic is a gap of reef distribution. Real reefs (The term “real reef” is used to exclude stromatolite “reefs”) did not resume till the Middle Triassic Anisian. In the Anisian reefs were moderately developed. The Changhsingian reefs were mainly built by calcisponges and calcareous algae. The calcisponges include inozoans, thalamid sponges and sclerosponges, all with calcareous skeletons. Did any Changhsingian reef builders survive the end-Permian crisis? Some researchers (Flügel & Stanley, 1984) once claimed that some Permian thalamid sponges, such as Girtyocoelia persisted into the Early Triassic. But Flügel (1994) gave up this viewpoint in later paper. He believed that their similarities were actually morphological and they are really different organisms. Wu and Fan (2002) have examined all Permian and Triassic reefal thalamid sponge species and found that all Changhsingian thalamid sponge species disappeared at the end of the Permian. The thalamid sponges in the Middle Triassic Anisian reefs are all new species. Up to now, at least one species of rugose coral has been reported from Changhsingian reefs, Waagenophyllum (Fan et al., 1990; Xu et al., 1997; Liu et al., 1997). Like the coeval non-reefal rugose corals (Yang et al., 1991), this reefal rugose coral disappeared at the end of the Permian. Consequently, there are no rugose coral reefs in post-Permian strata. In sum, the end-Permian catastrophes killed all Changhsingian reefs as well as all Changhsingian reef-building calcisponges and rugose corals. |
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*Supported by National Natural Scientific Foundation of China (No. 40472015) and the State Key Laboratory of Modern Paleontology and Stratigraphy (No. 053102), as well as the Key Laboratory for Minerals and Resources, Chinese Academy of Sciences. |
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