Coelophysoids are the most abundant theropod dinosaurs known from the Late Triassic through Early Jurassic and represent the earliest major radiation of Neotheropoda. Within Coelophysoidea sensu lato, the most stable clade is Coelophysidae, which are small theropods characterized by long necks, and light and kinetic skulls. Coelophysids are the most abundant basal non-Tetanurae neotheropods known worldwide; however, until recently, they were unknown from South America. We report here a new coelophysid neotheropod, Lucianovenator bonoi gen. et sp. nov., from the late Norian—Rhaetian Quebrada del Barro Formation, northwestern Argentina. A phylogenetic analysis recovered Lucianovenator bonoi nested into the monophyletic group Coelophysidae in an unresolved clade, together with Coelophysis rhodesiensis and Camposaurus arizonensis. The presence of Lucianovenator in the late Norian—Rhaetian of Argentina increases the poor and scarce record of Triassic South American neotheropods, suggesting that the virtual absence of theropods in the fossil record during the Rhaetian is probably a taphonomic/ stratigraphic bias instead of a decline in diversity and abundance after the Norian. Finally, the new finding corroborates the American endemism of coelophysid neotheropods in the Late Triassic and their worldwide distribution during the Early Jurassic, supporting the extreme faunal homogeneity hypothesized for Early Jurassic continental biotas.

Neotheropoda includes the vast majority of the predatory dinosaurs and their oldest members are Late Triassic in age. The Triassic neotheropod record is restricted to North America and Europe with the exception of a few specimens from South America, which includes Zupaysaurus rougieri and Lucianovenator bonoi. Here, the South American record of the group is enriched with the description of the new genus and species Powellvenator podocitus from the middle Norian Los Colorados Formation (Ischigualasto-Villa Unión Basin) of northwestern Argentina. The new taxa are represented by previously undescribed partial hindlimbs collected by J. F. Bonaparte and associated to the hypodigm of the pseudosuchian Riojasuchus tenuisceps. In addition, a specimen originally interpreted by Bonaparte in 1972 as an indeterminate coelurosaur is here referred to the new species. Powellvenator podocitus differs from other basal dinosaurs in character-states that include an astragalus with a distinctly sigmoid posterodorsal margin and a rounded dorsal expansion on the anteromedial portion of the astragalar body in anterior view, calcaneum with a laterally projected flange, and strongly reduced shaft of metatarsal II. The phylogenetic relationships of the new species were tested in a comprehensive analyses focused on early neotheropods, which recovered Powellvenator podocitus within Coelophysoidea and as the sister-taxon of Procompsognathus triassicus and Coelophysinae. Powellvenator podocitus represents the first coelophysoid from South America together with Lucianovenator bonoi from the Marayes-El Carrizal Basin.

A fragmentary postcranial skeleton from the Late Jurassic (Oxfordian—Tithonian) Cañadón Calcáreo Formation of Chubut, Argentina, represents a new taxon of theropod dinosaur, which is here described as Pandoravenator fernandezorum gen. et sp. nov. This material represents the first Late Jurassic theropod known from Argentina. Pandoravenator fernandezorum is characterized by strongly elongated postzygapophyses in the caudal vertebrae and an unusual tarsal joint, with the astragalus showing two distal tubercles and a very low and laterally inclined ascending process. Phylogenetic analyses indicate that the new taxon is a basal tetanuran, although its exact phylogenetic position within basal tetanurans remains uncertain, due to the fragmentary nature of the remains and the lack of consensus among the different phylogenetic analyses. The tarsus of P. fernandezorum shows an intermediate morphology between that of basal theropods and more derived tetanurans. It is especially noteworthy for the presence of a suture between the distal astragalar condyles and the anteroproximal extension of the astragalus, including the ascending process. This indicates that a separate ossification of the ascending process of the astragalus was present in this taxon, and, in a phylogenetic context, thus provides evidence that the origin of the ascending process and the astragalar body from separate ossifications was already present at the base of Averostra.

Many dinosaur skeletons show evidence of behavior, including feeding, predation, nesting, and parental care. The resting posture of the forelimbs has been studied in some theropod species, in relation to the acquisition of flight in advanced maniraptoran theropods. Chilesaurus diegosuarezi is a bizarre tetanuran recently described from the Toqui Formation (latest Tithonian) of southern Chile that is represented by multiple well-preserved and articulated specimens. The aim of the present work is to analyze the forelimb posture of four articulated specimens of Chilesaurus diegosuarezi, focusing on its anatomical description, and phylogenetic and behavioral implications. All the preserved specimens show strongly ventrally flexed arms with the hands oriented backwards, an arrangement that closely resembles those in dinosaur specimens previously described as preserving resting posture, such as Mei long, Sinornithoides youngi and Albinykus baatar. As a result, it seems that individuals of Chilesaurus diegosuarezi have been in passive activity (e.g. feeding, resting) when they were buried quickly, allowing their fossilization in life position and preserving the forelimb resting posture. The arrangement of the forelimb bones in Chilesaurus could show the first evidences of the structures linked to the muscles that flex the forearms, features related with the acquisition of flying control in advanced maniraptorans.

A new genus and species of ornithomimosaur, Afromimus tenerensis, is described based on a fragmentary skeleton from the Lower Cretaceous (Aptian—Albian) El Rhaz Formation of Niger. The holotype and only known individual preserves caudal vertebrae, chevrons and portions of the right hind limb. Derived ornithomimosaurian features include the broad, peanut-shaped articular surfaces of mid caudal centra, parasagittal fossae on mid caudal centra for reception of the postzygapophyses of the preceding vertebra, and a raised, subtriangular platform on the ventral aspect of the pedal phalanges. New information is given for, and comparisons made to, Nqwebasaurus thwazi from southern Africa, the oldest and most basal ornithomimosaur. Unlike other coelurosaurian clades that have expansive radiations on northern landmasses, the oldest ornithomimosaur and now another basal form are known from a southern landmass, Africa.

A detailed description of the neuroanatomy of Murusraptor barrosaensis—a mid-sized non-maniraptoran theropod from the Late Cretaceous of north Patagonia—is based on the exceptionally preserved type braincase. CT scans provide new information on the braincase, brain, cranial nerves, encephalic vasculature, and inner ear of this taxon. Worldwide, relatively few non-maniraptoran theropod braincases have been described in detail and the new information reported here is important to better understand the variability of braincase characters within the clade. This study suggests that megaraptorids have a particular brain pattern that is different from those of other non-coelurosaur theropods, such as allosauroids and ceratosaurs, and different from that of some coelurosaurs, such as tyrannosaurids, although sharing more similarities with the latter. The Reptile Encephalization Quotient of Murusraptor is within a range between those of Allosaurus and Tyrannosaurus; the Olfactory Ratio is, however, smaller than the observed in tyrannosaurids and allosauroids. The paleobiological implications on gaze stabilization, hearing, and olfaction in the Argentinean taxon are still poorly understood.