Plant megafossils resembling Cooksonia caledonica Lang are described f
rom the Kirusillas Formation in southern Bolivia. Faunal and lithologi
cal evidence together with field relationships advocate a late Siluria
n (Ludlow) age. Palaeocontinental reconstructions suggest that the pla
nts grew on the western edge of Gondwana at 50-60 degrees S and indica
te that Cooksonia had spread to higher latitudes soon after its appear
ance in the Wenlock.