Biotic recovery following the P/Tr crisis

Delayed recovery? (current dating: Early Triassic = c. 2 millions years )
Recovery occurred in the Middle Triassic? (fast recovery cases (or initial recovery) may have occurred in the Early Triassic?)
Various fossil groups have different recovery rates following the P/Tr extinction
Major factors affecting biotic recovery following the mass extinction

Brachiopoda, or lamp shells, is an ancient group. Fewer than 300 species survive today, but the 30,000 fossil species have been described. Brachiopods are all attached bottom-dwelling marine forms that mostly prefer shallow water. Externally they resemble bivalve mollusks in having two calcareous shell valves secreted by the mantle. However, they have dorsal and ventral valves rather than right and left lateral valves.

Biotic recovery after modern and ancient defaunation events: What are the similarities and differences in the response of the marine ecosystem to biotic crises at different scales? The diagram below shows my model of how the benthic marine ecosystem recovered after the end-Permian mass extinction event. In the immediate aftermath of the event only the very shallowest tiers were occupied; predominantly by deposit feeders (stage 1). The shallow infaunal suspension feeders returned next (2), followed by the higher epifaunal tiers (3). Eventually tiering levels above and below the sediment surface returned to pre-extinction levels (4).

Objectives:
Testing interactions between marine communities and environments during P/Tr mass extinction & subsequent recovery

Methods
1. Marine communities throughout P-Tr transition
Alpha diversity, taxonomic/ecologic dominants, bioturbation extent, tiering, Bamchachian megaguilds & sedimentary structures

Diversity indices (Shannon & Simpson indices and Dominance) were calculated using the paleontological statistical
analysis package PAST (Hammer et al., 2001).

The Shannon index evaluates the diversity of paleo-community, whereas both Simpson index and
Dominance (= 1-Simpson index) evaluate the evenness of the community.