Scampering, trotting, walking tridactyl bipedal dinosaurs in southern Africa: ichnological account of a Lower Jurassic palaeosurface (upper Elliot Formation, Roma Valley) in Lesotho

Abstract

In Gondwana, Early Jurassic dinosaur track sites are especially concentrated in Lesotho. Despite intensive investigations during the third quarter of the twentieth century, a limited number of vertebrate track sites of this country have been studied with rigorous ichnological and sedimentological methodology. Here, we present a previously mentioned, but undescribed track site in the upper Elliot Formation (Hettangian?) of Lesotho, located near Roma (at Lephoto dam). Two tridactyl ichnite morphologies, made by bipedal vertebrate trackmakers are recognised. The first can be identified as Grallator-like, an ichnotaxon common in the Lower Jurassic of both Laurasia and Gondwana that can be attributed to small and medium-size theropod dinosaurs. In contrast, the second ichnite type is reminiscent of Trisauropodiscus, which is a rare ichnotaxon that resembles tracks of small birds and is known with certainty in Lesotho from only a few places. We suggest that at our upper Elliot Formation study site, Trisauropodiscus was potentially made by a heterodontosaurid ornithischian dinosaur. Our work provides further evidence that the ichnological record of the Stormberg Group of southern Africa is in a unique position to shed light not only on Early Jurassic biostratigraphy and palaeoenvironments but also on the biodiversity and palaeobiology of early dinosaurs.

Graphical Abstract

Keywords:

• Trisauropodiscus
• Grallator
• Early Jurassic
• ornithischian dinosaur
• avian-like tracks
• southern Gondwana

Acknowledgements

We thank our dear friend, Me’ Malefu Nhlapo for her enthusiastic site cleaning efforts, local guiding and cheerful camaraderie in the past 18 years. Me’Ma’fu you rock! We are indebted to Prof David Ambrose (formerly of National University of Lesotho) for his guidance on the Roma track sites and genuine interest in our work. We are also very grateful to the Editor as well as reviewers Gerard Gierlínski and anonymous for their insightful comments and suggestions that helped us improve this manuscript.