disparity seems to have been intermediate, both in terms of the loss of major clades and for the few clades where disparity has been quantitatively assessed. Reef builders were heavily impacted by this episode, with colonial tabulate corals virtually disappearing as significant constructors. Together with the significant loss of stromatoporoids, this extinction caused a major shift in reef types that persisted into the Permian (Wood, 1999; Flügel and Kiessling, 2002). There are too few studies of this event on which to assess its impact on phylogenetic, behavioral, or developmental diversity.
Two major extinction episodes close out the Permian, one at the end of the Guadalupian, of which much less is known, and the most severe mass extinction of the Phanerozoic at the close of the Permian (Erwin, 2006a). The loss of taxonomic diversity during this interval was higher than during any other event, some 82% of marine genera and 54% of marine families (Sepkoski, 1996). Phylogenetic analyses of articulate brachiopods, bryozoans, and gastropods reveal a considerable loss of diversity. The impact on morphological disparity is apparent from the large number of clades lost (trilobites, blastoids, and the tabulate and rugose corals) or severely affected (articulate brachiopods, echinoids, ammonoids, radiolarians, bryozoans, and foraminifera). The loss of disparity is confirmed by quantitative studies of disparity among brachiopods (Ciampaglio, 2004), ammonoids (McGowan, 2004), and crinoids and blastoids (Foote, 1992, 1999). Carbon isotopes indicate a significant loss of primary productivity (Jin et al., 2000) that persisted for ≈2 million years (Payne et al., 2004; Erwin, 2007b). The most pervasive indication of the functional and ecological impact of this extinction was that the marine communities of the Ordovician-Permian, dominated by epifaunal, suspension feeding brachiopods, byozoans, and pelmatazoan echinoderms, simply vanished (Erwin, 2006a). A large suite of reef types had developed by the Middle Permian, virtually all of which disappeared, leaving a gap in metazoan-constructed reefs during the Early Triassic (Wood, 1999; Flügel and Kiessling, 2002). Detailed investigations of trace fossils have revealed a significant loss of diversity with only a few types of shallow burrows occurring in earliest Triassic sections (Twitchett and Wignall, 1996; Twitchett and Barras, 2004). I have ranked the loss of developmental diversity as moderate because of both the loss of major clades and major subclades.
In the Late Triassic, ammonites and bivalves experienced the greatest extinction. There are few studies on which to assess the extent of loss of phylogenetic or developmental diversity or morphologic disparity. Although there are few studies of paleoecological patterns across this boundary, much less studies of food web structure, there is little evidence for major disruptions of functional diversity except among reefs, where a major drop in sea level triggered a substantial decline in reef volume