Living fossils in a petrified forest

James O’Donoghue (UK) It’s a Welwitschia!  Nestling among 280 million year old fossil tree trunks, this is the rare plant I have been searching for. Two wonders of the natural world – the living, sprawling Welwitschia and the ancient, petrified trees – have fortuitously come together here in Namibia. Separated by more than an immense period of time, they also bear witness to completely different environments. Welwitschia is adapted to the extremes of dryness and heat of a desert while the archaic trees once lined a great floodplain and were felled by melting glacial waters. However, in spite of their many differences, these two plants share a hidden secret. Between them, they reveal the fascinating story of a gigantic landmass that broke apart over 100Ma. Fig. 1. Petrified log showing segmentation caused by compressional stress. The ancient southern supercontinent of Gondwana existed for hundreds of millions of years and embraced South America, Africa, Madagascar, Australia, Antarctica and parts of Asia. By 280mya, vast cool temperate forests of Cordaites trees covered parts of Gondwana. Cordaites is a primitive relative of the conifers that grew to 30m in height and is best known from the coal swamp forests of 325 to 295mya in Europe and North America. As Gondwana emerged from a great ice age, Cordaites trees lining river floodplains were engulfed by melting glacial waters. This catastrophic flooding resulted in their burial under hundreds of metres of sediment. Over an immense period of time, silica dissolved in groundwater replaced the original … Read More

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