Fos­sil leaves should make waves

Grocott's Mail - - OUTSIDE TURNING OVER LOGS - By STEVEN LANG

Sci­en­tists are only scratch­ing the sur­face of South Africa's plant fos­sil her­itage, said Dr Rose Prevec dur­ing her talk at the Al­bany Mu­seum last week. She said that an­cient forests from the Per­mian Pe­riod (299 to 252 mil­lion years ago) in what is now the Ka­roo, have barely been stud­ied.

When new di­nosaur bones are dis­cov­ered, or a type of an­cient hu­man an­ces­tor is found in a cave, sci­en­tists, the me­dia and the gen­eral pub­lic can be­come very ex­cited. How­ever, when a rich new site of fos­sil leaves is dis­cov­ered, it is much harder to get the pub­lic’s at­ten­tion.

Prevec is one of two palaeob­otanists cur­rently em­ployed in South Africa. The only other mem­ber of this rather rare breed is Prof Mar­ion Bam­ford who works for the Evo­lu­tion­ary Stud­ies In­sti­tute at the Univer­sity of the Wit­wa­ter­srand. The pro­fes­sion is soon to have a third mem­ber as Aviwe Mati­wane is cur­rently study­ing fos­sil Glos­sopteris leaves as part of her PhD research.

Prevec was speak­ing about the im­por­tance of these an­cient forests to our present econ­omy as part of a lec­ture se­ries on the earth sciences. She ex­plained that plant ma­te­rial de­posited dur­ing the Per­mian Pe­riod was trans­formed into coal through a slow process in­volv­ing burial, com­pres­sion, heat­ing and chem­i­cal al­ter­ation. Coal formed over mil­lions of years is to­day the prime gen­er­a­tor of elec­tri­cal en­ergy in South Africa and there­fore a key driver of our econ­omy.

Mati­wane gave the fi­nal lec­ture of the four-part se­ries fo­cus­ing on re­cent dis­cov­er­ies of Glos­sopteris fos­sils near the town of Suther­land in the North­ern Cape.

Glos­sopteris is a genus of more than 70 shrubs and trees that thrived dur­ing the Per­mian but abruptly dis­ap­peared in the largest ever ex­tinc­tion event at the end of that pe­riod. This plant de­rived its name from the Greek work "glossa" which means tongue be­cause the leaves are usu­ally shaped like a long tongue.

The plants took var­i­ous forms with some trees reach­ing up to 30m tall. When they were first dis­cov­ered it was be­lieved that they were a type of fern, but cur­rently glos­sopterids are placed in with the gym­nosperms (conifers, cy­cads and others).

Glos­sopteris fos­sils have been found in South­ern Africa, South Amer­ica, In­dia, Aus­tralia and Antarc­tica. Their pres­ence in these dif­fer­ent land masses pro­vide com­pelling ev­i­dence of the ex­is­tence of the Gond­wana su­per con­ti­nent dur­ing the Per­mian Pe­riod.

At the time when Glos­sopteris trees dom­i­nated the Gond­wana land­scape, the world looked very dif­fer­ent to what we might ex­pect to­day. We would be sur­prised to find out that there was no grass on the ground, no flow­ers any­where at all, no birds, no true mam­mals and the di­nosaurs were still far off in the fu­ture.

Photo: Steven Lang Photo: Dr Rose Prevec

Glos­sopteris leaves from the Late Per­mian Pe­riod (ap­prox­i­mately 252 mil­lion years old) taken from a rail­way cut­ting in north­ern KwaZulu-Natal, near Richards Bay.

Dr Rose Prevec, Cu­ra­tor and Head of the Depart­ment of Earth Sciences at the Al­bany Mu­seum.

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