Lanthanosuchus watsoni (Efremov 1946) Late Permian ~253 mya skull: 10 cm, was considered by deBraga and Reisz (1996) and Cisneros et al. (2004) to be a sister taxon to Acleistorhinus, which is a clear mismatch. Here, in this larger, more inclusive study, Lanthanosuchus was derived from a sister to Macroleter and Romeriscus (see below). Lanthanosuchus was a phylogenetic dead end.
Distinct from Macroleter, the skull of Lanthanosuchus was flatter and wider, but otherwise comparable in most respects. The lateral temporal fenestra was larger than the orbit that expanded dorsally into the postorbital. The postparietals were reduced. The tabulars were expanded to the size of the supratemporals. Quadratojugal "horns" were retained. The surface of the bone was strongly pitted and various bumps protruded. The teeth were all smaller.
As in Macroleter, the neural spines were inflated.
The postcrania of Romeriscus (see below) gives us the best estimate for the post-crania of Lanthanosuchus.