Müller, Langer and Dias da Silva (2018) report:
“Despite representing a key-taxon in dinosauromorph phylogeny, Lagerpertidae is one of the most obscure and enigmatic branches from the stem that leads to the dinosaurs.”
It’s taxon exclusion, yet again.
Lagerpeton (Fig. 1) is obscure and enigmatic because it is NOT in the stem that leads to dinosaurs. We discussed that earlier here in 2011. Langer is aware of the better, more inclusive, option because he sent me the reference for Novas and Agnolin 2016 discussed here.
“Recent new findings have greatly increased our knowledge about lagerpetids, but no phylogenetic analysis has so far included all known members of this group. Here, we present the most inclusive phylogenetic study so far conducted for Lagerpetidae. …Finally, quantification of the codified characters of our analysis reveals that Lagerpetidae is one of the poorest known among the Triassic dinosauromorph groups in terms of their anatomy, so that new discoveries of more complete specimens are awaited to establish a more robust phylogeny.”
Tropidosuchus is known from complete skeletons (Fig. 1) and is the sister to Lagerpeton in the more inclusive large reptile tree (LRT, 1173 taxa).
Müller et al. nest Ixalerpeton (Fig. 24) with Lagerpeton without testing other candidates. In the LRT Ixalerpeton nests among basal protorosaurs, far from Lagerpeton. And yes, it might have been the only bipedal protorosaur, exciting news that was completely overlooked due to taxon exclusion. Or not. The foot would be helpful, but is not known.
Müller RT, Langer MC & Dias-Da-Silva S 2018. Ingroup relationships of Lagerpetidae (Avemetatarsalia: Dinosauromorpha): a further phylogenetic investigation on the understanding of dinosaur relatives. Zootaxa 4392(1): 149â158
Novas FE and Agnolin FL 2016 Lagerpeton chanarensis Romer (Archosauriformes): A derived proterochampsian from the middle Triassic of NW Argentina. Simposio. From Eventos del Mesozoico temprano en la evolución de los dinosaurios”. Programa VCLAPV. Conferencia plenaria: Hidrodinámica y modo de vida de los primeros vertebrados. Héctor Botella (Universitat de València, España) 2016