Testing Feeserpeton

A new paper on a new basal reptile skull, Feeserpeton oklahomensis (Macdougall and Reisz 2012, Figs. 1-3, Early Permian) brings us yet another wonderful non-synapsid with a large lateral temporal fenestra.

Feeserpeton skull.

Figure 1. Feeserpeton skull. This non-synapsid nests with Millerosaurs closest to Australothyris, very close to Acleistorhinus. Pink on occiput is where the missing tabulars would go. Pink and blue on palate represents unexposed areas of the palate covered by the mandibles. Premaxilla and jugal are largely missing.

Macdougall and Reisz (2012) considered Feeserpeton a “parareptile” and nested it with Acleistorhinus (Fig. 3) and Lanthanosuchus [what is THAT doing in there??]. Australothyris (Figs. 2, 3) was the outgroup taxon followed by Microleter and Eunotosaurus + Milleretidae and the mesosaurs [what are THEY doing in there??] in that order. Their tree included 30 taxa and 136 characters. It recovered 22 trees. Thankfully they picked most of the right taxa, but they did include several suprageneric taxa, which is always a problem.

How Feeserpeton nested in their study is only slightly problematic
Lanthanosuchus + Acleistrohinus scored a 56 in decay analysis (Macdougall and Reisz 2012). With Feeserpeton added that raised that node score to 70, which is good, but not great. Australothyris is the sister to this clade. It must have lowered the score below 50 because that node is unmarked.

The large reptile tree nested Feeserpeton with Australothyris within the Millerettidae, a clade that includes Acleistorhinus, but not Lanthanosuchus.

Figure 2. The large reptile tree nested Feeserpeton with Australothyris within the Millerettidae, a clade that includes Acleistorhinus, but not Lanthanosuchus.

The large reptile tree found another nesting. 
Here  completely resolved (Fig. 2) Feeserpeton nested as a sister to Australothyris (Fig. 3). They shared so many traits (121 of 128 skull traits) that another paleontologist might have considered Feeserpeton a species of Australothyris. The RC14 specimen of Milleretta is very close to the base of these two. Only one step is added when shifted over.

Acleistorhinus turns out to be a close relative, but closer to Eunotosaurus. However, Lanthanosuchus is the strange bedfellow here, 5 major nodes away–way, way off with Macroleter.

Of the seven traits that the large reptile tree found that separated Feeserpeton from Australothyris, three involved orbit size/shape vs. the postorbital region of the skull. Feeserpeton has the only canine in the clade, if you call that one big fat broken tooth a canine. Feeserpeton has an unfused supraoccipital/ophisthotic, but Australothyris fuses these elements. The frontal is wider posteriorly in Australothyris, but not in Feeserpeton. That’s it! Everything else, 121 traits, scores the same. Decay analysis would have a hard time pulling these two apart.

Competing closely related candidates Acleistorhinus, Feeserpeton and Australothyris to scale.

Figure 3. Competing closely related candidates Acleistorhinus, Feeserpeton and Australothyris to scale. The postorbitals are more similar in the upper two, but Feeserpeton nests with Australothyris. The lacrimal/naris connections along with the presence of a large quadratojugal nest these two taxa together, among 121 other traits.

The following traits were unique to Australothyris and Feeserpeton
1. Dorsal nasal shape widest at mid length. 2. Major axis of naris greater than 30 degrees. 3. Naris opening anterior. 4. Maxilla ventral shape convex. 5. Orbit at  least equal to rostrum length. 6. Frontal/nasal angle is a zigzag. 7. Squamosal and quadratojugal not indented. 8. Quadrate lateral coverage minimal. 9. Jaw joint orientation lined up with jawline. 10. Occiput shape has parallel lateral sides (not converging). 11. Pterygoid transverse processes with single row of teeth. 12.Posterior mandible without a noticeable coronoid process.

Predictions
Australothyris
predicts that Feeserpeton will have more than 4 teeth in each premaxilla, and that Feeserpeton will have tabulars and a gracile jugal.

As always, I encourage readers to see specimens, make observations and come to your own conclusions. Test. Test. And test again.

Evidence and support in the form of nexus, pdf and jpeg files will be sent to all who request additional data.

Reference
Macdougall MJ and Reisz R 2012.
A new parareptile (Parareptilia, Lanthanosuchoidea) from the Early Permian of Oklahoma, Journal of Vertebrate Paleontology, 32:5, 1018-1026.

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