An unusual new archosauriform from the Middle-Late Triassic of southern Brazil and the monophyly of Doswelliidae

Abstract

Until now the Doswelliidae was considered a monospecific family including Doswellia kaltenbachi from the Late Triassic of North America. The phylogenetic position of this taxon remained enigmatic until recently, when a sister-group relationship with the Proterochampsidae was suggested. In the present contribution we describe the new doswelliid species Archeopelta arborensis gen. et sp. nov. from the Middle-Late Triassic of Brazil. A cladistic analysis recovered Archeopelta, Doswellia, and Tarjadia within a monophyletic group of basal archosauriforms, the Doswelliidae. The monophyly of this family is supported by the presence of osteoderm ornamentation that is coarse, incised, and composed of regular pits and the presence of an unornamented anterior articular lamina. Archeopelta is more closely related to Doswellia than to other archosauriforms by the presence of basipterygoid processes anterolaterally orientated, dorsal centra with a convex surface, width of the neural arch plus ribs of the first primordial sacral that are three times the length of the neural arch, and iliac blade laterally deflected, with strongly convex dorsal margin, and a length less than three times its height. The phylogenetic analysis indicates that Doswellidae is the closest large monophyletic entity to Archosauria, which achieved a wide palaeolatitudinal distribution during the late Middle and Late Triassic time span.

Proterochampsa barrionuevoi (Archosauriformes: Proterochampsia) from the Late Triassic (Carnian) of Argentina and a phylogenetic analysis of Proterochampsia

“…Proterochampsians span the Middle and Late Triassic of Argentina and Brazil. Three species of Middle Triassic (Ladinian) or possibly earliest Carnian (Desojo et al . 2011) proterochampsians, Chanaresuchus bonapartei (Romer 1971), Gualosuchus reigi (Romer 1971) and Tropidosuchus romeri (Arcucci 1990), are found in the Chañares Formation, La Rioja Province, Argentina.…”

“…Age of the Dinodontosaurus Assemblage Zone is likely Ladinian to early Carnian and coeval with the Chañares Formation (Langer et al . 2007; Desojo et al . 2011).…”

“…2003) of the Santa Maria Formation (Langer et al . 2007) probably Late Carnian in age (Desojo et al . 2011).…”

A new species of the enigmatic archosauromorph Doswellia from the Upper Triassic Bluewater Creek Formation, New Mexico, USA

“…2011). As recognized by Desojo et al . (2011), the Doswelliidae consist of three genera ( Doswellia , Tarjadia and Archeopelta ), the latter two known only from fragmentary specimens.…”

“…We note that the ‘longitudinal rows’ of osteoderms Dilkes and Sues (2009) referred to are best considered ‘columns’ of osteoderms sensu Heckert and Lucas (1999), who describe aetosaur carapaces in terms of longitudinal columns (parallel to the vertebral column) and transverse rows (often but not always one row per vertebral position). This convention can thus also be applied to the armour of nonaetosaurian archosauromorphs, as shown by Desojo et al . (2011), who also followed this terminology in their recent review of the Doswelliidae.…”