including very cold winters and temperate summers supporting the Glossopteris flora, which would have been restricted to sheltered basins. Later, other studies, mainly based on climate models, also suggested a cold temperate climate with high thermal amplitude between summer (+15 to +20 °C) and winter (-20 to -25 °C). More recent studies also indicate a temperate climate, but with much less severe winters than those previously suggested. Keddy Yemane thus suggested that the vast river system and the many giant lakes present at the time throughout southern Africa must have significantly moderated the continentality of the Karoo climate during most of the Permian. Paleobotanical studies focusing on the characteristic morphology of plant leaves and the growth rings of fossil woods also indicate a seasonal climate with summer temperatures of up to 30 °C and free-frost winters. According to Richard Rayner, the high southern latitudes experienced very hot and humid summers, with an average of 18 hours of light per day for more than four months during which precipitation was comparable to the annual amount falling in the present-day tropics. These conditions were extremely conducive to rapid growth in plants such as Glossopteris. The habit in Glossopteris of losing its leaves at the beginning of the bad season would be linked to a shorter duration of daylight rather than the existence of very cold winter temperatures. From the geochemical study of sediments from several Karoo sites, Kay Scheffler also obtains a temperate climate (with mean annual temperatures of about 15 to 20 °C), with free-frost winter, but with an increase in aridity during the Middle Permian. Paleoecology The sediments of the Abrahamskraal Formation consists of a succession of sandstones, and versicolor siltstones and mudstones, deposited by large rivers that flowed from south to north from the Gondwanide mountain range. These large rivers of variable sinuosity drained a vast alluvial plain that sloped gently down to the northeast toward the Ecca sea (a former landlocked sea), while in receding phase. The landscape was composed of marshy land, interrupted by rivers, lakes, woods and forests. Many fossil traces (footprints, ripple marks, mudcracks) indicate that swampy areas, which were the most extensive habitat, were frequently exposed to the open air and should not often be deeply flooded. The vegetation was dominated by the deciduous pteridosperm Glossopteris, which formed woodlands and large forests concentrated along the streams and on the uplands. Large horsetails ( high),