Styracocephalus x2 enters the TST

Fraser-King et al. 2019
bring us new data on Styracocephalus (Fig. 3), a purported dinocephalian therapsid from Late Permian South Africa. Unfortunately the Fraser-King et al. phylogenetic analysis (Fig. 1) excludes relevant taxa (like Phthinosuchus) and includes one unrelated taxon, Tetraceratops. The authority for this criticism is a larger study, the therapsid skull tree (TST, 72 taxa, subset Fig. 2) a side branch of the large reptile tree (LRT, 1579 taxa). It includes the relevant taxa in the Fraser-King et al. study, and many more excluded from Fraser-King et al.

Figure 1. Cladogram from Fraser-King et al. 2019. Compare to figure 2 where many more taxa are included.

Figure 1. Cladogram from Fraser-King et al. 2019. Compare to figure 2 where many more taxa are included. Tetraceratops is not related to any therapsid, but nests closer to Limnoscelis.

FIgure 2. TST with the addition of two specimens attributed to Styracocephalus and Raranimus. Compare to fewer taxa in figure 1.

FIgure 2. TST with the addition of two specimens attributed to Styracocephalus and Raranimus. Compare to fewer taxa in figure 1. Here Styracocephalus is not related to tapinocephalids. The TST is fully resolved.

Both the holotype of Styracocephalus
and the new referred specimen nest together in the LRT despite their many morphological differences (Fig. 3). Even so, I think the differences are strong enough to erect a new genus for the new specimen. The two nest with the Phthinosuchus clade in the LRT, a taxon not included in the Fraser-King et al. study.

Figure 1. At left, the holotype of Sclerocephalus SAM PK 8936. At right the distinctly different referred specimen to scale BPI I 7141.

Figure 3. At left, the holotype of Sclerocephalus SAM PK 8936. At right the distinctly different referred specimen to scale BPI I 7141.

So, in this case,
I’m a splitter, not a lumper. And I wish Fraser-King et al. had included a few more taxa.

PS
Raranimus also entered the TST because Fraser-King included that taxon. Raranimus nested with Ictidorhinus, and ironically, could be congeneric given how little is known of Raranimus.


References
Fraser-King S, Benoit J, Day MO and Rubidge BS 2019. Cranial morphology and phylogenetic relationship of the enigmatic dinocephalian Styracocephalus platyrhynchus from the Karoo Supergroup, South Africa. Palaeontologia africana 54: 14–29.

 

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