NATURE GEOSCIENCE | ADVANCE ONLINE PUBLICATION | www.nature.com/naturegeoscience 1 news & views T he end-Permian mass extinction about 252 million years ago set the course for the prevailing biota in today’s oceans 1 . During this extinction — which was the most severe of the past 500 million years — most marine organisms, including the bottom-dwelling brachiopods and crinoids that had reigned the oceans of the Palaeozoic, were decimated. he forerunners of modern burrowing clams, grazing and carnivorous snails, and predatory crustaceans, took the lead. Despite the extreme loss of diversity, the number of novel higher-order taxa that evolved in the extinction’s atermath was relatively low. However, mass extinctions do not only devastate biodiversity — they also oten fundamentally restructure the variety of functions performed by the biota 2 . Writing in Nature Geoscience, Foster and Twitchett 3 show that, on a global scale, the primary ecological modes of making a living on the sea loor remained remarkably stable in number, even though temporary losses in speciic marine settings were severe. he ecospace occupied by a marine organism is characterized by three ecological variables: mobility, feeding mechanism and living location 4 . hus a typical Permian brachiopod might be considered a suricial, stationary, attached suspension feeder, whereas most burrowing clams are classiied as shallow infaunal, facultatively motile, unattached suspension feeders. Attempting to reconstruct the ecosystem functions of an ancient biota requires not only knowledge about the life habit of the extinct organisms, but also reliable data on the temporal and spatial distribution of the organisms and the survival of the taxa through the extinction. Two complementary data sets of fossil occurrence and range, combined with better tools to correct for uneven sampling 5 , now allow such an analysis. With the help of these data and tools, Foster and Twitchett 3 assess the persistence of marine bottom-dwelling genera from the Late Permian to Middle Triassic periods. hey conclude that, on the global scale, just a single mode of life out of 28 was irrecoverably lost at the end of the Permian. Partly buried, stationary, unattached deposit feeders vanished as a consequence of the extinction of one poorly studied class of molluscs — the rostroconchs. Likewise, in the atermath of the extinction, only one new mode of life emerged: erect, limited mobile, attached suspension feeders appeared with the evolution of motile crinoids in the Early Triassic (Fig. 1). he lack of ecospace vacated during the extinction could explain why, even though taxonomic diversity collapsed to levels similar to the early Palaeozoic, only a few higher taxa and just one novel mode of life originated in the early Mesozoic. MASS EXTINCTIONS Ecological diversity maintained The end-Permian extinction decimated marine life on an unprecedented scale. However, an analysis of the lifestyles of the surviving genera shows that very little functional diversity was lost at the sea loor. Martin Aberhan c d a b e Relative diversity Modes of life 260 258 256 254 252 250 248 246 244 242 240 238 25 30 Age (Ma) Late Permian (Lopingian) Early Triassic Middle Triassic Wuchiapingian Changhsingian Gries- bachian Dienerian Smithian Spathian Aegean Bithynian Pelsonian Illyrian Fassanian Longo- bardian Induan Olenek- ian Anisian Ladin- ian Timescale Figure 1 | Ecological change across the end-Permian mass extinction in the global marine benthic ecosystem. a, By tracking the occurrence of higher taxa all the way from irst to last occurrence, Foster and Twitchett 3 demonstrate overall stability in the number of modes of life. b,c, Only the ecospace occupied by rostroconchs was irreversibly emptied when this group went extinct in the Permian period (b), and just one novel mode of life appeared in the Triassic with the evolution of motile crinoids (c). d,e, Nevertheless, severe extinctions within permanently attached suspension feeders (d), radiations within slow-moving grazers (e) and other changes quantiied by Foster and Twitchett 3 led to a diferent ecological structure in the Triassic. Ma, millions of years ago. © 2014 Macmillan Publishers Limited. All rights reserved