二叠纪-三叠纪礁相房室海绵演化与灭绝

就礁相房室海绵而言，早二叠世的物种数最少，中二叠世的分异度最高,晚二叠世的其次，中三叠世的较少，卡尼斯的增多,诺利期的更多。礁相房室海绵的演化反映出二叠纪－三叠纪有3次灭绝事件，分别发生在中二叠世末期、长兴期末期、卡尼期末期。这3次灭绝事件的规模各不相同：中二叠世末期的灭绝事件规模较小，它使83．8％的中二叠世礁相房室海绵种灭绝；长兴期末期的灭绝规模最大，它使100％的长兴期种灭绝；卡尼期末的灭绝事件规模也较大，它使97．7％的卡尼期种灭绝。

PERMIAN-TRIASSIC HISTORY OF REEFAL THALAMID SPONGES: EVOLUTION AND EXTINCTION

All described Permian Triassic reefal thalamid sponges are checked under the same taxonomic standard of species and those incorrectly assigned are placed respectively in the right taxon. Then the thalamid sponges of different Permian Triassic periods are compared at specific level in this study. The division of Permian System by Jin et al. (1997) (Table 1) and that of Triassic System by Harland et al . (1989) (Table 2) are followed. All described thalamid sponges from Permian and Triassic reefs are included in the study, except for those without pictures, which makes it impossible for us to check their identification. Pictures of all described thalamid sponges used in the study have been compared to the picture of the monotype of a given species and those inappropriately identified by previous researchers were assigned to the right taxon. In previous studies medium size (diameter > 0.5 cm) and large size (diameter >1 cm) thalamid sponges caught more attention. On the contrary, small thalamid sponges were mostly overlooked. In this study small thalamid sponges in the Changhsingian reefs of Ziyun, Guizhou Province, China are also included.