Cecilia Apaldetti; Ricardo N. Martinez; Oscar A. Alcober; Diego Pol

“ Since PVL 4087 lacks diagnostic characters, we interpret the specimen as a non-sauropod sauropodomorpha incertae sedis. Consequently, the rationale for the Norian age of the Quebrada del Barro Formation proposed by Bossi and Bonaparte [20] is pulled into question.
The close affinities of the new specimen reported here with the basal sauropodomorph Adeopapposaurus [19] , as well as the close affinity of these two taxa with the Early Jurassic sauropodomorph Massospondylus from South Africa likely indicates a younger age for Quebrada del Barro Formation. ”

“ In order to test the affinities of these taxa in relation to massospondylids, we have run a constrained analysis with a Sarahsaurus + Ignavusaurus clade and with Seitaad placed within Massospondylidae. The search retrieves 70 MPTs that are six steps longer than the MPTs of the unconstrained search (1307 steps, CI: 0.324 and RI: 0.665) . The strict consensus of the constrained analysis depicts a polytomy formed by Massospondylus, Seitaad, Coloradisaurus (Glacialisaurus + Lufengosaurus) , and Sarahsaurus + Ignavusaurus as a sister clade to the Adeopapposaurus + Leyesaurus clade. ”

“ The third cervical centrum is 30% longer than the axial centrum similar to Herrerasaurus and other basal sauropodomorphs (such as Riojasaurus, Plateosaurus and Yunnanosaurus) , but different from the much more elongated C3 of Coloradisaurus and Adeopapposaurus (which is twice as long as the axis) . The anteroposterior length of the anterior cervical centra is more than 4 times its dorsoventral height, whereas the sixth vertebra has the greatest elongation, with a centrum 5.12 times longer than tall (Figure 7B; see Table S1 for measurements) . ”

“ This group is supported by a Bremer support value of 2 and bootstrap frequencies below 50% (Figure 13, Figure S1) .
The clade formed by Massospondylus, Adeopapposaurus, and Leyesaurus is placed as the sister group of the clade formed by Coloradisaurus, Lufengosaurus and Glacialisaurus. This group resembles the Massospodylidae of Yates [31] , but our results imply an expanded taxonomic content for Massospondylidae, a group that is diagnosed by seven unambiguous synapomorphies: dorsal profile of the snout with a depression behind the naris (character 20.1, unknown in Leyesaurus) ”

“ Distal tarsal III is proximodistally flat, has a subtriangular shape and its major axis is oriented anterolaterally (Figure 11A–B) . The anterolateral region is proximodistally thin and increases in thickness towards its posteromedial region, where the distal tarsal III reaches its deepest portion (Figure 11B) . The posterolateral surface has two ligament pits (Figure 11B) and the posteromedial surface bears a large pit that is internally divided. Distal tarsal IV is hemicone shaped and is larger than distal tarsal III (Figure 11C–D) . ”

“ Character scorings changed for Adeopapposaurus mognai in comparison with scorings provided by Sertich and Loewen [55] . 3) Scorings for all taxa analysed in the phylogenetic analyses of the modified version of the data matrix of Yates [32] . 4) Strict consensus with Bremer support and Bootstrap (absolute frequencies) values. 5) Complete list of synapomorphies. (DOCX) (data file pone.0026964.s003.docx) We are indebted to Benito Leyes, a local goatherder who found the specimen in 2001 and collaborated with the field crew of the Instituto y Museo de Ciencias Naturales de San Juan (IMCN) . ”