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A hidden cradle of plant evolution in Permian tropical lowlands

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Science  21 Dec 2018:
Vol. 362, Issue 6421, pp. 1414-1416
DOI: 10.1126/science.aau4061

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Late Permian seed-plant evolution

The great evolutionary expansion of seed plants took place in the Mesozoic era, which began after the Permian mass extinction 252 million years ago. Blomenkemper et al. report the discovery of seed-plant fossils from Late Permian (252-million- to 260-million-year-old) deposits on the margins of the Dead Sea in Jordan. This area represents an equatorial habitat with pronounced dry seasons. These fossils, which include the earliest records of conifers, push back the ages of several important seed-plant lineages. Some of these lineages appear to span the mass extinction event at the end of the Permian, which suggests that the communities they supported may have been more stable than expected over this transition. Thus, early evolutionary innovations can occur in drought-prone tropical habitats—which rarely offer the conditions needed for fossil preservation.

Science, this issue p. 1414

Abstract

The latitudinal biodiversity gradient today has deep roots in the evolutionary history of Earth’s biota over geologic time. In the marine realm, earliest fossil occurrences at low latitudes reveal a tropical cradle for many animal groups. However, the terrestrial fossil record—especially from drier environments that are thought to drive evolutionary innovation—is sparse. We present mixed plant-fossil assemblages from Permian equatorial lowlands in present-day Jordan that harbor precocious records of three major seed-plant lineages that all became dominant during the Mesozoic, including the oldest representative of any living conifer family. These finds offer a glimpse of the early evolutionary origins of modern plant groups in disturbance-prone tropical habitats that are usually hidden from observation.

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