LATE PERMIAN (LOPINGIAN) TERRESTRIAL ECOSYSTEMS: A GLOBAL COMPARISON WITH NEW DATA FROM THE LOW LATITUDE BLETTERBACH BIOTA

In this presentation we review the composition of the 14 best-documented late Permian terrestrial ecosystems. For each ecosystem we provide a quantitative characterization of the fauna (body fossil and ichnofossil records), the relative abundances of floral groups, and climatic and palaeolatitudinal settings. We find that both floral and faunal bioprovinces were strongly affected by the distribution of climate regimes, and that latitude was a predictor of ecosystem compositional affinity. The Bletterbach biota (S Alps, Italy), together with ecosystems from Morocco and Niger, provides a unique window on equatorial to low latitude life and yields evidence that the most diverse assemblages at high taxonomic levels are those at mid to low latitudes. Although fossil-rich, higher latitudes ecosystems (e.g., Junggar and Karoo) are much less diverse at high taxonomic levels.

Climatic constraint appears crucial in shaping the distribution of the three main herbivorous groups. Dicynodonts were best adapted to cool temperate climates with glossopterid/conifer-dominated woodlands. Pareiasaur distribution best correlates with conifer- and ginkgophyte-rich woodlands that developed in the warm temperate climate of equatorial to sub-equatorial Pangaea. Captorhinid distribution is consistent with the semi-arid to arid conditions of the tropical summerwet biome, where they might have fed on “pteridosperms" and conifers.

Climate, latitude and tectonic history controlled the affinity of the different ecosystems. North Gondwanan ecosystems had closer affinities with Euramerican than to south Gondwanan ecosystems. The Laotian ecosystem shows affinity with Karoo-type ecosystems, likely inherited before the northward migration of SE Asian continental blocks.

The Lopingian latitudinal gradient shows a poleward decline in tetrapod richness. Tropical assemblages include a mixture of holdovers from the early Permian (e.g., temnospondyls, captorhinids), early members of clades best known in the Triassic (e.g., Archosauriformes), and contemporary taxa that also are present at higher latitudes (e.g., therapsids, pareiasaurs), suggesting that the tropics acted as both as a cradle (i.e., an area with elevated origination rates) and a museum (i.e., an area with low extinction rates) for biodiversity.