HABIT AND ECOLOGY OF THE PETRIELLALES, AN UNUSUAL GROUP OF SEED PLANTS FROM THE TRIASSIC OF GONDWANA

BOMFLEUR, BENJAMIN; DECOMBEIX, ANNE-LAURE; SCHWENDEMANN, ANDREW; ESCAPA, IGNACIO; TAYLOR, EDITH L.; TAYLOR, THOMAS N.; MCLOUGHLIN, STEPHEN

INTERNATIONAL JOURNAL OF PLANT SCIENCES

UNIV CHICAGO PRESS

Lugar: Chicago; Año: 2014 vol. 175 p. 1062 - 1075

1058-5893

Premise of research. Well-preserved Triassic plant fossils from Antarctica yield insights into the physi- ology of plant growth under the seasonal light regimes of warm polar forests, a type of ecosystem without any modern analogue. Among the many well-known Triassic plants from Antarctica is the enigmatic Petriellaea triangulata, a dispersed seedpod structure that is considered a possible homologue of the angiosperm carpel. However, the morphology and physiology of the plants that produced these seedpods have so far remained largely elusive.Methodology. Here, we describe petriellalean stems and leaves in compression and anatomical preser- vation that enable a detailed interpretation of the physiology and ecology of these plants.Pivotal results. Our results indicate that the Petriellales were diminutive, evergreen, shade-adapted pe- rennial shrubs that colonized the understory of the deciduous forest biome of polar Gondwana. This life form is very unlike that of any other known seed-plant group of that time. By contrast, it fits remarkably well into the ?dark and disturbed? niche that some authors considered to have sheltered the rise of the flowering plants some 100 Myr later.Conclusions. The hitherto enigmatic Petriellales are now among the most comprehensively reconstructed groups of extinct seed plants and emerge as promising candidates for elucidating the mysterious origin of the angiosperms.