FIGURE 1. The end-Permian mass extinction of tetrapods in the South Urals basin, Russia.

The data show diverse and complex ecosystems in the Late Permian, with rapid turnover among families between the stratigraphic units. After the mass extinction, diversity and ecosystem complexity were much reduced. Recovery taxa lasted longer through the Early and Middle Triassic, and turnover was much reduced as ecosystems reassembled. Solid lines indicate that the family is known from the time bin in question; dashed lines indicate Lazarus taxa²². Families are plotted by broad-scale ecological categories, based on major habitat (freshwater or terrestrial), diet (fish, browsing, insects, tetrapods) and size (small, medium, large), in accordance with categories and classifications in ref. 29. Completeness of the record is documented to the right by numbers of localities and specimens from each svita, and quality of the fossils is divided into four classes (1, isolated bone; 2, several associated bones; 3, complete or near-complete skull; 4, complete or near-complete skeleton). The timescale of svitas (based on field criteria) and gorizonts (based on fossil assemblages) are the Russian standards for the South Urals basin^14,15, and correlation with international timescales is from refs. 10, 23 and 24. The approximate positions of the South African tetrapod assemblage zones are indicated. Boundaries for which good radiometric dates exist are indicated with filled circles. Br., browsers; Chang., Changhsingian; In., insect-eaters; Kung., Kungurian; Loc., localities; Spec., specimens; Tet., tetrapod-eaters.