Melanorosaurus readi Haughton, 1924 (Dinosauria, Sauropodomorpha) from the Late Triassic of South Africa: osteology and designation of a lectotype

ABSTRACT

The sauropodiform sauropodomorph dinosaur Melanorosaurus readi Haughton, 1924, from the lower Elliot Formation (Norian) of South Africa, has had a checkered taxonomic history. This is due to the lack of published information on the original syntype material and the use of referred specimens as the primary source of anatomical information on the taxon. Here, we present a revised osteology of Melanorosaurus based solely on the syntype series and argue that the latter includes the remains of a single, associated individual that we designate the lectotype. The species can be diagnosed on the basis of features of the caudal vertebrae and ilium but we restrict the hypodigm to the lectotype pending detailed reassessment of all referred specimens. Melanorosaurus has been used as an external specifier in the definition of Sauropoda, but given the fragmentary nature of the material, its lack of clear ‘sauropod-like’ features, and its phylogenetic lability we suggest that this is no longer appropriate.

DATA AVAILABILITY STATEMENT

The authors confirm that the data supporting the findings of this study are available within the article and its supplementary files.

DISCLOSURE STATEMENT

No potential conflict of interest was reported by the author(s).

ACKNOWLEDGMENTS

We offer our sincere thanks to C. Browning (SAM), J. Botha and E. Butler (NMQR), S. Jirah (BP), and P. Ortiz (PVL) for permission to access specimens in their care. Special thanks go to Z. Skosan (SAM) for facilitating the many changes to register numbers and specimen housing that were required to make sense of the Melanorosaurus hypodigm, as well as providing other collections assistance. M. van der Westhuizen (SAM) is also thanked for help. B. Weiss (BP) created the map in Figure 1 using data supplied by P. Viglietti (BP) and S. Wills (NHMUK). Scott Hartman is thanked for providing the skeletal reconstruction presented in Figure 2. We are grateful to the Willy Hennig Society for providing free access to TNT. C. Peyre de Fabrègues, an anonymous reviewer, and the editors (H.-D. Sues, P. Godoy, and M. D’Emic) provided useful comments on an earlier version of this paper. PMB’s trips to South Africa were supported by the Earth Sciences Departmental Investment Fund (Natural History Museum, U.K.) and data collection in Argentina was funded by a Royal Society International Exchange Grant (with D. Pol, who helped arrange access to these collections); JNC was funded by GENUS: the DSI-NRF Centre of Excellence, Palaeosciences, and by the NRF African Origins Platform (grants 118794 and 136516).

AUTHOR CONTRIBUTIONS

PMB and JNC conceived the project, collected data, analyzed the data, and contributed jointly to the writing of the manuscript.

SUPPLEMENTARY FILES

Supplementary File 1.docx: additional details of phylogenetic analysis.

Supplementary File 2.tnt: modified version of McPhee et al. (2018) dataset.

Supplementary File 3.nex: modified version of McPhee et al. (2018) dataset.

Supplementary File 4.tre: all trees obtained from modified McPhee et al. (2018) dataset.

Supplementary File 5.tre: all trees obtained from constrained analysis using modified McPhee et al. (2018) dataset.

Supplementary File 6.tnt: modified version of Pol et al. (2021) dataset.

Supplementary File 7.nex: modified version of Pol et al. (2021) dataset.

Supplementary File 8.tre: all trees obtained from modified Pol et al. (2021) dataset.

Supplementary File 9.tre: all trees obtained from constrained analysis using modified Pol et al. (2021) dataset.