The Cretaceous Carcharodontosauridae is the latest clade of carnosaurs, including the largest predatory dinosaurs yet recorded. Albeit spectacular for their size, the skeletal anatomy of these theropods remains poorly-known, and their diversity was until recently restricted to two Cenomanian species: the highly derived Giganotosaurus carolinii, from southern South America, and the incompletely known Carcharodontosaurus saharicus, from northern Africa. Here we describe an older and basal member of the group, Tyrannotitan chubutensis gen. et sp. nov., from Aptian strata of Patagonia, Argentina. The new taxon gives new insights into the systematics and evolution of carcharodontosaurids and offers a better understanding of the evolution of Southern theropod faunas. We suggest that carcharodontosaurids radiated in Gondwana sharing with spinosaurids the role of top-predators until their extinction in Cenomanian-Turonian times. During this interval, the diplodocoid sauropods and giant titanosaurians went extinct (probably as part of a global-scale crisis), and the smaller abelisaurid theropods took dominance, reigning until the end of the Cretaceous. Electronic Supplementary Material is available.

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This paper contains the first comprehensive ichnotaxonomic review of the Triassic tetrapod track record in Argentina, including previous accounts and new material recently discovered, and an analysis of its composition and stratigraphic distribution. Triassic footprints have been recorded from three basins: the Ischigualasto-Villa Unió n and Cuyo basins in north-west Argentina, and the Los Menucos depocentre in northern Patagonia. Most are in successions of Middle Triassic age; a lower number are from the Late Triassic, and there are two records from Early Triassic rocks. The known track types include: Brachychirotherium isp., cf. Brachychirotherium isp., Chirotherium barthii, Dicynodontipus ispp., Grallator isp., Rhynchosauroides isp., Rigalites ischigualastianus, Rigalites isp., Tetrasauropus isp., and bird-like, chirotheriid and unidentified tridactyl footprints. The ichnogenera Gallegosichnus Casamiquela, 1964, Calibarichnus Casamiquela, 1964, Palaciosichnus Casamiquela, 1964 and Stipanicichnus Casamiquela, 1975 are considered to be synonyms of Dicynodontipus (Hornstein, 1876). In addition, the abandonment of the following ichnogenera (and single ichnospecies) that are based on poorly preserved material is suggested: Ingenierichnus sierrai Casamiquela, 1964, Rogerbaletichnus aguilerai Casamiquela, 1964 and Shimmelia chirotheroides Casamiquela, 1964. At least eight Triassic ichnofaunas can be recognized. The most peculiar is that of the Late Triassic Los Menucos depocentre, which is characterized by the dominance of therapsid footprints (Dicynodontipus ispp.). The track assemblages from the Cuyo Basin display the highest ichnodiversity, with five footprint types.

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