Miscellaneous notes #1: Limnoscelis and Saurorictus

A few loose ends
from the large reptile tree (LRT) that I failed to mention earlier:

#1
Saurorictus (Fig. 1; Late Permian; Modesto and Smith 2001; SAM PK-8666), nesting at the base of the captorhinids and their basal lepidosauromorph sisters, is the proximal outgroup taxon in the LRT for Limnoscelis. Except for size, the resemblance is striking and, so far, unreported in traditional paleontology.

Sadly,
Wikipedia still thinks of Limnoscelis as a “reptile-like diadectomorph (a type of reptile-like amphibian).” Romer 1946 and Willistion 1911 pegged it as a reptile.

While we’re on the subject of the Limnoscelidae
the 2011 nesting of Tetraceratops (Fig. 2) with Tseajaia and Limnoscelis in the LRT has not been challenged. Relying on taxon exclusion, Tetraceratops was nested as a basal therapsid most recently by Amson and Laurin 2011 and earlier by other studies that excluded other clades. The thin squamosal broken into smaller pieces that drifted into the orbit were overlooked and ignored by earlier studies. The convergence is interesting, though. Spindler 2014 did question the nesting of Tetraceratops as a basal therapsid, but only on the basis of a trait list, not by expanding their taxon list to Tseajaia and its sisters. 

wiki/Saurorictus
wiki/Limnoscelis

Tetraceratops References
Amson E and Laurin M 2011. On the affinities of Tetraceratops insignis, an Early Permian synapsid. Acta Palaeontologica Polonica 56(2):301-312. online pdf 
Conrad J and Sidor CA 2001. Re−evaluation of Tetraceratops insignis (Synapsida: Sphenacodontia). Journal of Vertebrate Paleontology 21: 42A.
Matthew WD 1908. A four-horned pelycosaurian from the Permian of Texas.
Bulletin of the American Museum of Natural History 24:183-185.
Laurin M and Reisz RR. 1996. The osteology and relationships of Tetraceratops insignis, the oldest known therapsid. Journal of Vertebrate Paleontology 16:95-102. doi:10.1080/02724634.1996.10011287.
Sidor CA and Hopson JA 1998. “Ghost lineages and “mammalness”: Assessing the temporal pattern of character acquisition in the Synapsida”. Paleobiology 24: 254–273.
Spindler F 2014. Reviewing the question of the oldest therapsid. Paläontologie, Stratigraphie, Fazies (22) Freiberger Forschungshefte C 548: 1–7.

wiki/Tetraceratops