Martensius enters the LRT between Milleretta and the Caseasauria

Figure 1. Ffrom Berman et al. 2020, skull of Martensius in two views, plus full scale.

Figure 1. Ffrom Berman et al. 2020, skull of Martensius in two views, plus full scale.

Martensius bromackerensis (Berman et al. 2020; Early Permian, 50cm; MNG 13814 adult holotype; MNG 14230 juvenile and smallest specimen; Figs. 1, 2) is the basalmost taxon in the caseasauria, derived from Milleretta (Fig. 4) in the large reptile tree (LRT, 1660+ specimens; subset Fig. 3). Four specimens of Martensius were found together, from a juvenile to an adult. A small skull is apparent here, a trait that continues in most caseasaurs. Uniquely the majority of the bottom of the naris is the maxilla.

Figure 2. The juvenile specimen of Martensius.

Figure 2. The juvenile specimen of Martensius.

Berman et al. did not test the outgroup taxon,
Milleretta, nor any casesaur kin, like Feeserpeton, Australothyris, Acleistorhinus, Eunotosaurus, nor any other lepidosauromorphs in their phylogenetic analysis. Instead they  followed tradtion by assuming casesaurs were synapsids. Testing invalidated that hypothesis of interrelationships several years ago.

Figure 3. Subset of the LRT with Martensius added to the base of the Caseasauria + another clade of similar lepidosaurs, all derived from Milleretta.

Figure 3. Subset of the LRT with Martensius added to the base of the Caseasauria + another clade of similar lepidosaurs, all derived from Milleretta.

The authors expressed some concern
about Eocasea, which they considered basal to the Caseasauria. It is, but only when several taxa are omitted (see Fig. 3 for that list). Add taxa and such concerns go away. Adding taxa minimizes taxon exclusion problems. Eocasea nests closer to Delorhynchus than to any caseasaur.

Figure 2. Milleretta, caseasaurs and kin. The LRT nests these taxa together apart from the Synapsida, with which they share a lateral temporal fenestra.

Figure 4. Milleretta, caseasaurs and kin. The LRT nests these taxa together apart from the Synapsida, with which they share a lateral temporal fenestra.

On a similar note,
earlier another group of paleontologists considered a taxon ‘a bird/dinosaur’ in amber when it was really a lepidosaur. The finger-pointing thereafter was pretty intense. I don’t expect the same sort of upwelling to attend this phylogenetic mistake because Berman et al. considered a taxon a synapsid when it was really a lepidosauromorph. This corner of the phylogenetic tree doesn’t touch as many emotional buttons and the big Kahuna has not yet reached a wider audience. Taxon exclusion remains the problem.


References
Berman DS, Maddin HC, Henrici AC Sumida SS, Scott D and Reisz R 2020. New primitive caseid (Synapsida, Caseasauria) from the Early Permian of Germany. Annals of the Carnegie Museum 86(1):43–75.

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