The origin of Limnoscelis

Limnoscelis, according to Wikipedia, “is a genus of large (1.5 m in total length), very reptile-like diadectomorph (a type of reptile-like amphibian) from the Early Permian of North America. Contrary to other diadectomorphans, Limnoscelis appear to have been a carnivore. Though the post cranial skeleton is very similar to the early large bodied reptiles like pelycosaurs and pareiasaurs, the digits lacked claws, and the bones of the ankle bones were fused like in other reptile-like amphibians. This would not allow them to use their feet actively in traction, but rather as holdfasts, indicating Limnoscelis primarily hunted slow moving prey.”

Figure 1. Limnoscelis and two suitable ancestral taxa, Orobates and Milleretta, all shown to scale (below) and to fit (above).

Figure 1. Limnoscelis and two suitable ancestral taxa, Orobates and Milleretta, all shown to scale (below) and to fit (above).

The large reptile tree nested Limnoscelis well within the Lepidosauromorpha branch of the Reptilia/Amniota along with the smaller Orobates and not far from tiny Milleretta (Fig. 1). The latter two are the most suitable ancestral morphologies yet found on the large reptile tree.

Limnoscelis and Orobates do not nest with Diadectes and other diadectomorphs, but also, not too far away from that clade. The Limnoscelis clade still nests with Tseajiaia and Tetraceratops.

Are those carnivorous teeth in Limnoscelis?
Most sister taxa in surrounding clades are likely herbivores. Some related taxa had canines, but not Limnoscelis.

When are we going find consensus
on the nesting of Limnoscelis? We need a competing large gamut phylogenetic analysis to confirm or refute the topology recovered by the large reptile tree. Either that, or let the results of the large reptile tree get published.

Berman DS, Reisz RR and Scott D 2010. Redescription of the skull of Limnoscelis paludis Williston (Diadectomorpha: Limnoscelidae) from the Pennsylvanian of Canon del Cobre, northern New Mexico: In: Carboniferous-Permian Transition in Canon del Cobre, Northern New Mexico, edited by Lucas, S. G., Schneider, J. W., and Spielmann, New Mexico Museum of Natural History & Science, Bulletin 49, p. 185-210.
Romer AS 1946. The primitive reptile Limnoscelis restudied American Journal of Science, Vol. 244:149-188
Williston SW 1911. A new family of reptiles from the Permian of New Mexico: American Journal of Science, Series 4, 31:378-398.




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