Reviving Kalosauropus, an Early Jurassic sauropodomorph track from southern Africa (Lesotho)

ABSTRACT

Kalosauropus, the ‘beautiful reptile track’, was collected from the Sinemurian–Pliensbachian lower Clarens Formation (upper Stormberg Group) in Lesotho in the 1950s. It was formally described in 2003 when it was transferred to Otozoum, an ichnogenus known in North America, Europe and Africa, and associated with basal sauropodomorphs. This transfer has been questioned due to the significant morphological differences between these two tracks, leaving Kalosauropus in taxonomical limbo. Using digital imaging techniques, herein we demonstrate that diagnostic and quantifiable morphological differences between Kalosauropus and Otozoum justify their separation as two independent ichnogenera. The size-range of Kalosauropus reported from a single site indicates that the bipedal trackmakers were likely juveniles or small-bodied animals. The co-occurrence of morphologically similar but different sized tracks suggests social behaviour among these Early Jurassic trackmakers. Using osteological evidence and foot bone measurements, we also show that Kalosauropus may be attributed to a bipedal massospondylid, representing the iconic and common basal sauropodomorph family from the Early Jurassic of southern Africa. Reinstating Kalosauropus thus not only expands the Early Jurassic sauropodomorph footprint record in southern Gondwana, but also provides a more nuanced understanding of the ichnotaxonomic complexities surrounding the early dinosaurian track record that spans the Triassic-Jurassic boundary globally.

GRAPHICAL ABSTRACT

KEYWORDS:

• Tetradactyl track
• Early Jurassic
• lower Clarens Formation
• southern African Karoo
• basal sauropodomorph dinosaur
• massospondylid

Acknowledgments

We acknowledge curators Ms Suzanne Jiquel for access to the Ellenberger Collection at the Universitè de Montpellier (France), Mr Michel Zondo at the Natural History Museum of Zimbabwe, Ms Zaituna Skosan at the Iziko South African Museum and Drs Bernhard Zipfel and Sifelani Jirah at the ESI for access to the massospondylid collections. We also express our special thanks to Ntate Stephen Gill and Mme` Keletso Selialia Lesego at the Morija M&A in Lesotho for not only granting us access to the Morija track collection, but also for companionship and encouragement during our repeated visits. We are thankful to Dr Fabien Knoll and Dr Raquel López‐Antoñanzas not only for many insightful discussions on the Early Jurassic palaeontology of the southern Africa but also for accommodating us and being wonderful hosts during our study visit in Montpellier. We thank Dr Miengah Abrahams and Mr Akhil Rampersadh for taking the initial pictures of some of the track casts in the Morija M&A. We are grateful to Dr Blair McPhee for discussions and advice on trackmaker anatomy and palaeontology, and the UCT dino trackers, Akhil Rampersadh and Howard Head, for their field assistance, feedback and overall camaraderie during this project.

We also thank reviewers Spencer Lucas and an anonymous reviewer for meaningfullycontributing with their insightful comments to the overall quality of this study.

Opinions expressed and conclusions reached are those of the authors and are notnecessarily to be attributed to the CoE in Palaeosciences or NRF or anybody else.

Disclosure statement

The authors receive no financial benefit from this research.

Data archiving statement

The data that support the findings of this study are openly available in Figshare at

https://doi.org/10.6084/m9.figshare.12055275

The archived data includes:

a) Table of ichnological morphometric parameters of Kalosauropus, including standard track and trackway measurements, and speed calculations.

b) Ichnological photogrammetric data: photographs used in the photogrammetric models, and the cleaned and aligned 3D models as recommended by Falkingham et al. (2018).

This published work has been registered in ZooBank:

http://zoobank.org/References/07807ff8-8eab-4bb7-b63d-13865f47723e

Supplementary material

Supplemental data for this article can be accessed here.

Additional information

Funding

The work was supported from the following research grants obtained by EMB (as PI): National Research Foundation (NRF) of South Africa Competitive Programme for Rated Researches (CPRR) and African Origins Programme (AOP) [grant numbers 93544, 113394, 98825] and DST-NRF Centre of Excellence in Palaeosciences [grant numbers CoE PAL 2019 2020]. Postgraduate bursaries were received by RM from the National Research Foundation (NRF) of South Africa and DST-NRF Centre of Excellence in Palaeosciences (2019–2020).