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The Middle Triassic uppermost Omingonde Formation of Namibia records a fossil tetrapod fauna including stahleckeriid dicynodonts and probainognathian and traversodontid cynodonts, similar to other ...

Crown group Archosauria, which includes birds, dinosaurs, crocodylomorphs, and several extinct Mesozoic groups, is a primary division of the vertebrate tree of life. However, the higher-level phylogenetic relationships within Archosauria are poorly resolved and controversial, despite years of study. The phylogeny of crocodile-line archosaurs (Crurotarsi) is particularly contentious, and has been plagued by problematic taxon and character sampling. Recent discoveries and renewed focus on archosaur anatomy enable the compilation of a new dataset, which assimilates and standardizes character data pertinent to higher-level archosaur phylogeny, and is scored across the largest group of taxa yet analysed. This dataset includes 47 new characters (25% of total) and eight taxa that have yet to be included in an analysis, and total taxonomic sampling is more than twice that of any previous study. This analysis produces a well-resolved phylogeny, which recovers mostly traditional relationships within Avemetatarsalia, places Phytosauria as a basal crurotarsan clade, finds a close relationship between Aetosauria and Crocodylomorpha, and recovers a monophyletic Rauisuchia comprised of two major subclades. Support values are low, suggesting rampant homoplasy and missing data within Archosauria, but the phylogeny is highly congruent with stratigraphy. Comparison with alternative analyses identifies numerous scoring differences, but indicates that character sampling is the main source of incongruence. The phylogeny implies major missing lineages in the Early Triassic and may support a Carnian-Norian extinction event. Fil: Brusatte, Stephen L.. University of Bristol; Reino Unido Fil: Benton, Michael J.. University of Bristol; Reino Unido Fil: Desojo, Julia Brenda. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales “Bernardino Rivadavia”; Argentina. Bayerische Staatssammlung fur Paläontologie und Geologie; Alemania Fil: Langer, Max C.. Universidade de Sao Paulo; Brasil

Synopsis Study of aetosaurian archosaur material demonstrates that the dermal armour of Desmatosuchus chamaensis shares almost no characters with that of Desmatosuchus haplocerus. Instead, the ornamentation and overall morphology of the lateral and paramedian armour of ’D.’ chamaensis most closely resembles that of typothoracisine aetosaurs such as Paratypothorax. Autapomorphies of ’D.’ chamaensis, for example the extension of the dorsal eminences of the paramedian plates into elongate, recurved spikes, warrant generic distinction for this taxon. This placement is also supported by a new phylogenetic hypothesis for the Aetosauria in which ’D.’ chamaensis is a sister taxon of Paratypothorax and distinct from Desmatosuchus. Therefore, a new genus, Heliocanthus is erected for ’D.’ chamaensis. Past phylogenetic hypotheses of the Aetosauria have been plagued by poorly supported topologies, coding errors and poor character construction. A new hypothesis places emphasis on characters of the lateral dermal armour...