Lotosaurus adentus (Zhang 1975) Ladinian, Late Middle Triassic ~240 mya, 2.5 m in length. Nesbitt (2003) considered Lotosaurus a rauisuchid close to Arizonasaurus, but it bears only a superficial resemblance. The spine sails were convergent. Weinbaum and Hungerbuhler (2007) assigned Lotosaurus to the Poposauridae (Effigia + Shuvosaurus) in 2007, which agrees with the present study. Brusatte et al. (2010) also kept Lotosaurus with the poposaurids, but also brought in Arizonasaurus, Yarasuchus and Qianosuchus, which are more distantly related.

Distinct from Silesaurus the skull of Lotosaurus was shorter, taller and had no teeth. The premaxilla was relatively larger and the maxilla relatively shorter.

The cervical series was compressed. All the neural spines were taller, the result of elongated scutes fused to underlying bone.

The scapula was massively expanded. The rest of the forelimb was robust. See Ticinosuchus for the phylogenetically closest manus, which was structurally similar, but shorter.

Distinct from Silesaurus, the pubis extended ventrally and was relatively shorte and shorter than the ischium. The hindlimbs were more robust. Digits II and III were the longest. Atypical for this clade digits 1 and 5 were robust, following the pattern seen in Qianoschus, Ticinosuchus, Scleromochlus and Gracilisuchus.

Ctenosauriscus koeneni (von Huene 1902, originally Ctenosaurus) Olenekian, latest Early Triassic, was originally considered a type of pelycosaur close to Dimetrodon that had somehow survived into the Triassic. Further discoveries and studies placed it with contemporary rauisuchians like Arizonasaurus. But was it more closely related to the dinosaur, Lotosaurus? I can't tell with the present data. Distinct from Lotosaurus, the sail portion of the vertebrae originated further anteriorly, over the mid cervicals and was overall much taller, but then it lived tens of millions of years later.

A recent online paper by Butler et al. (2011) reports: "Both analyses recover a monophyletic Ctenosauriscidae that excludes Lotosaurus, but includes Arizonasaurus, Xilousuchus, Ctenosauriscus, the Waldhaus taxon, and Hypselorhachis. The most consistent characters supportining Ctenosauriscidae are the great elongation of the dorsal neural spines, and the fact that these elongated neural spines are curved along their length.

Butler RJ, Brusatte SL, Reich M, Nesbitt SJ, Schoch RR, et al. 2011. The Sail-Backed Reptile Ctenosauriscus from the Latest Early Triassic of Germany and the Timing and Biogeography of the Early Archosaur Radiation. PLoS ONE 6(10): e25693. doi:10.1371/journal.pone.0025693 Plos One paper

Nesbitt SJ 2003. Arizonasaurus and its implications for archosaur divergence
Sterling J. Nesbitt Proceedings of the Royal Society, London B (Suppl.) 270, S234–S237. DOI 10.1098/rsbl.2003.0066

Weinbaum JC and Hungerbuhler A 2007. A Revision of Poposaurus gracilis (Archosauria: Suchia) based on two new specimens from the Late Triassic of the southwestern USA. Palaeontologische Zeitschrift 81(2):131-145.

Zhang F-K 1975. A new thecodont Lotosaurus, from Middle Triassic of Hunan. Vertebrata PalAsiatica 13:144-147.

wiki/Lotosaurus