Figure 2. Field occurrences of the enigmatic horizontal, regularly-oriented structures from the Lower Jurassic Clarens Formation of southern Africa. The structures commonly occur in great profusion, en masse on horizontal surfaces up to 100 m ² ( 1 - 2 ) as well as in localized, smaller (eroded) patches ( 5 ). The density of the structures is typically extremely high ( 1 - 2 ), but locally only a few, rather loosely spaced structures are present ( 3 ). Side views ( 4 - 5 ) show that the structures have spherical cross-sections (see black circles in E), uniform diameters (~5 mm) and are preserved as full relief ( 4 - 5 ) or epirelief ( 1, 2, 3, 5 ). Also note that the thickness of the strata in which these structures occur varies from a few cm to over 0.5 m ( 4 ). 1-3 bedding plane views; 4 side view; 5 mainly bedding plane view, upper right and lower left corners side views.