Hidden for one hundred years: a diverse theropod ichnoassemblage and cross-sectional tracks from the historic Early Jurassic Tsikoane ichnosite (Clarens Formation, northern Lesotho, southern Africa)

Abstract

The upper Stormberg Group of Lesotho has an abundant and diverse ichnological record that dates to the Early Jurassic. Herein, we re-evaluate a known ichnosite in the lowermost Clarens Formation (Karoo Supergroup) at Tsikoane in northern Lesotho. The site was reported to preserve tridactyl tracks as natural casts in the ceiling of overhangs and true track impressions on a fallen sandstone block. At least three track-bearing palaeosurfaces, associated with horizontally laminated sandstones and desiccated green mudstones, can be traced over a distance of 250 m. Associated with one of the track-bearing palaeosurfaces, discrete, U-shaped, cross-sectional structures are interpreted as a series of natural casts, surface tracks, true tracks and undertracks. Although the Tsikoane tracks were historically assigned to a single ichnogenus, later synonymised with Grallator, our findings show a higher diversity of tridactyl ichnites, with tracks that have Kayentapus-like and Eubrontes-like features in addition to previously recognised Grallator-like features. These new findings, within their high-resolution sedimentological context, improve the understanding of theropod palaeodiversity and palaeoecology in southern Africa during a crucial period in dinosaur history marked by increases in both abundance and diversity.