Lobalopex: Finally another therapsid enters the TST!

It’s been awhile
since the last therapsid was traced and scored. Today two taxa enter the TST.

Figure 1. Cladogram of ten taxa employed by Sidor et al. 2004.

Figure 1. Cladogram of ten taxa employed by Sidor et al. 2004.

Sidor, Hopson and Keyser 2004
introduced a new ‘biarmosuchian’ and ‘burnetiamorph” therapsid from the Permian of South Africa. They named their new find Lobalopex mordax (CGP/1/61, Fig. 2, skull length 15cm). They reported, “a cladistic analysis including ten biarmosuchian taxa indicates that Lobalopex is the sister taxon to Burnetiidae and that Lemurosaurus is the most primitive burnetiamorph.” (Fig. 1).

After testing
in the Therapsid Skull Tree (= TST, 73 taxa, Fig. 3) Lobalopex nested  as a member of the Burnetia clade, matching the nesting of Sidor, Hopsona and Keyser 2004.

Figure 1. Lobalopex added to previous nested burnetiidae.

Figure 2. Lobalopex added to previous nested burnetiidae. It has a longer skull than others in this clade. Look to Herpetoskylax to imagine an uncrushed Lobalopex skull.

Sidor et al.
note the dorsal skull is crushed (it looks melted!) dorsoventrally. The rest of the skull is not crushed. Photos of the original material have not been published. Look to Herpetoskylax (Fig. 2) to imagine an uncrushed Lobalopex skull (Fig. 2).

A tiny horn boss
is present on the rostrum of Lobalopex. That horn boss gets bigger in Proburnetia and Burnetia (Fig. 2), but skips Lemurosaurus. The ventral portion of the Lobalopex retroarticular process wa lost during collection. The supratemporals (bright green) are fused to underlying bones. Lobalpex has a longer rostrum, relative to orbit length, than others in its clade, convergent with Eotitanosuchus.

Strangely,
little to no post-cranial material is known from this clade. Was it an herbivore or carnivore?

Figure 3. TST with the addition of Lobalopex nesting in the Burnetia clade.

Figure 3. TST with the addition of Lobalopex nesting in the Burnetia clade.

Lobalopex is derived from Lemurosaurus
in Sidor, Hopson and Keyser (Fig. 1), but the other way around in the TST (Fig. 3). Ictidorhinus (Fig. 2) is the outgroup in both cladograms. Herpetoskylax was not mentioned by Sidor, Hopson and Keyser 2004 because it was published later, not until 2006.

Figure 4. More recent cladograms that include Herpetoskylax and Lobalopex.

Figure 4. More recent cladograms that include Herpetoskylax and Lobalopex.

More recent cladograms 
that include Herpetoskylax and Lobalopex (Kruger et al. 2015, Kammerer 2016; Fig. 4) presume Biarmosuchus is the outgroup taxon. By contrast in the TST (Fig. 3) Biarmosuchus is the outgroup to more derived therapsid taxa, as is Rubidgina (Fig.5), which also enters the TST (Fig. 3) today, nesting basal to gorgonopsids and therocephalians + cynodonts + mammals.

Figure 5. Rubidgina skull in 4 views. Note the wide cheeks rotating the orbits anteriorly.

Figure 5. Rubidgina skull in 4 views. Note the wide cheeks rotating the orbits anteriorly. This taxon is not basal to the Burnetia clade in the TST.

With Rubidgina added to the deep time lineage of humans
it would not be too far off the mark to say, the deep time ancestors of Little Red Riding Hood once looked quite a bit like the big bad wolf. How ironic. ‘Grandma’ really did have such big teeth!


References
Sidor CA, Hopson JA and Keyser AW 2004. A new burnetiamorph therapsid from the Teekloof Formation, Permian, of South Africa. Journal of Vertebrate Paleontology 24(4):938–950.

wiki/Lobalopex

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