Early Triassic vertebrate burrows from the Katberg Formation of the south-western Karoo Basin, South Africa

Abstract

Bordy, E.M., Sztanó, O., Rubidge, B.S. & Bumby, A. 2010: Early Triassic vertebrate burrows from the Katberg Formation of the south-western Karoo Basin, South Africa. Lethaia, Vol. 44, pp. 33–45. Very large (∼30–35 cm), uniform diameter cylindrical burrows were found at two localities, ∼100–110 m above Permo-Triassic boundary in the fluvial Katberg Formation (main Karoo Basin, South Africa). Analysis of their morphology and stratigraphical distribution allows us to improve both the understanding of the ethology of burrowing, and also the reconstruction of the earliest Triassic ecosystems. These burrows have a single opening that leads, via a large, uniform diameter, semi-horizontal tunnel, to a rounded terminus. These 3-m-long structures descend at angles of ∼30° to a maximum of 1.5 m depth. They are devoid of chambers, branching, cross-cutting, coiling or spiralling. Filled with coarse sediments, some have a <5-mm clay lining, and most have subtle indentations and various scratch marks. These burrows were possibly excavated as resting, hiding or aestivating shelters, and are tentatively attributed to dicynodonts (i.e. Lystrosaurus murrayi and L. declivis). Data suggest that burrowing was widespread after the P/Tr boundary event, when in this part of Gondwana, dryland fluvial systems had large fluctuations in flow with extended low-flow periods or drought punctuated by high-discharge periods. We hypothesize that these constructed refuges played a role in the biodiversity recovery and maintenance in the Early Triassic (Induan) ecosystem. □Early Triassic, Karoo Basin, Katberg Formation, South Africa, Tetrapod Burrows.