Combresomyces cornifer from the Triassic of Antarctica: Evolutionary stasis in the Peronosporomycetes

Structurally preserved fossil oogonia of Combresomyces cornifer (Peronosporomycetes) are found dispersed throughout silicified peat from Fremouw Peak, Antarctica. Fossil material is dated as early Middle Triassic, thus indicating a continuous presence of C. cornifer in the fossil record lasting at least 88 million years, and its survival through the Permian–Triassic mass extinction. Triassic specimens are morphologically identical to the type material from the upper Visean (Mississippian, Lower Carboniferous) of France, with the exception of size. The new fossils of C. cornifer provide additional insights into the evolutionary history and ecology of this long-ranging peronosporomycete, and demonstrate the persistence of this microorganism from the Mississippian to Middle Triassic with almost no morphological change with respect to the shape and morphology of its oogonium.