1 The systematic position of the enigmatic thyreophoran dinosaur Paranthodon africanus, 2 and the use of basal exemplifiers in phylogenetic analysis 3 4 Thomas J. Raven1,2 ,3 and Susannah C. R. Maidment2 ,3 5 61Department of Earth Science & Engineering, Imperial College London, UK 72School of Environment & Technology, University of Brighton, UK 8 3Department of Earth Sciences, Natural History Museum, London, UK 9 10Corresponding author: Thomas J. Raven 11 12Email address:
[email protected] 13 14 15 16 17 18 19 20 21ABSTRACT 22 23The first African dinosaur to be discovered, Paranthodon africanus was found in 1845 in the 24Lower Cretaceous of South Africa. Taxonomically assigned to numerous groups since discovery, 25in 1981 it was described as a stegosaur, a group of armoured ornithischian dinosaurs 26characterised by bizarre plates and spines extending from the neck to the tail. This assignment 27that has been subsequently accepted. The type material consists of a premaxilla, maxilla, a nasal, 28and a vertebra, and contains no synapomorphies of Stegosauria. Several features of the maxilla 29and dentition are reminiscent of Ankylosauria, the sister-taxon to Stegosauria, and the premaxilla 30appears superficially similar to that of some ornithopods. The vertebral material has never been 31described, and since the last description of the specimen, there have been numerous discoveries 32of thyreophoran material potentially pertinent to establishing the taxonomic assignment of the 33specimen. An investigation of the taxonomic and systematic position of Paranthodon is therefore 34warranted. This study provides a detailed re-description, including the first description of the 35vertebra. Numerous phylogenetic analyses demonstrate that the systematic position of 36Paranthodon is highly labile and subject to change depending on which exemplifier for the clade 37Stegosauria is used.