Ezcurra et al. 2018 review Garjainia

Ezcurra et al. 2018
intensively studied the Early Triassic erythrosuchid, Gargainia prima (Fig. 1; Otchev 1958) Early Triassic ~240 mya, 2 m. long) from Russia. The photographic images therein are remarkable for their clarity.

Figure 1. Garjainia at several scales and views.

Figure 1. Garjainia at several scales and views.

The authors report,
“We consider Vjushkovia triplicostata (Fig. 1) to be a junior synonym of Garjainia prima, (Fig. 1) because of their extremely similar morphology, with the two character states that differ between them being variable intraspecifically in some other diapsids.”  Others have considered Vjushkovia a junior synonym of Youngosuchus.


Figure 2. Erythrosuchids (white background) to scale. Note the differences between Vjushkovia and Garjainia. Click to enlarge.

That’s unfortunate.
Even without firsthand study, the large reptile tree (LRT, 1353 taxa) was able to clearly and cleanly split Garjainia from Vjushkovia (Fig. 3). As recovered here, Vjushkovia is not an erythrosuchid, but a basal rauisuchid, a clade derived from basal euarchosauriformes (Fig. 3) and separated from Erythrosuchidae by the clade Ornithosuchidae.

Figure 4. Subset of the LRT focusing on the Euarchosauriformes, including the Aetosauria.

Figure 3. Subset of the LRT focusing on the Euarchosauriformes, where Garjainia is a basal erythrosuchid and Vjushkovia is a basal rauisuchid. Proterosuchus nests outside of this clade.

The authors also report,
“A new phylogenetic analysis recovered a monophyletic Garjainia as sister to Middle Triassic erythrosuchids and recovered Fugusuchus hejiapanensis as sister to all other erythrosuchids.” 

Figure 4. Ezcurra et al. 2018 cladogram needs more taxa to clarify relationships.

Figure 4. Ezcurra et al. 2018 cladogram needs more taxa to clarify relationships. Compare to subset of the LRT in figure 3.

Ezcurra et al. 2018 omit so many pertinent taxa that their results (Fig. 4) do not match the more inclusive results of the LRT (Fig. 3). Pertinent taxa are listed online. Interested workers should insert pertinent taxa using their own character lists. As it stands, the Ezcurra et al. taxon list is far from complete and recovers an odd topology as a result.

Ezcurra 2016 recovered a clade Eucrocopoda that reappears for the first and only time again in Ezcurra et al. 2018. With more taxa, the LRT recovers a different topology and refutes the monophyly of the clade Eucrocopoda.

Once again
the primacy of the second-hand paleontologist hypothesis has been validated: It continues to be more important to have a wide gamut phylogenetic analysis of hundreds to thousands of specimens than to have first-hand access to a specimen in order to figure out (or recover) what an individual taxon is in the context of valid sister taxa. The bigger picture is misinterpreted when a wide gamut of taxa are omitted.

Ezcurra MD, Gower DJ, Sennikov AG and Butler RJ 2018. The osteology of the holotype of the early erythrosuchid Garjainia prima (Diapsida: Archosauromorpha) from the upper Lower Triassic of European Russia. Zoological Journal of the Linnean Society, 2018, XX, 1–67.
Otchev VG 1958. Novye dannye po pseudozukhiyam SSSR: Doklady Akademii Nauk SSR, 123(4):749-751.

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