Notosuchia represents one of the most morphologically diverse groups of Mesozoic crocodyliforms and was particularly abundant in the Cretaceous of Gondwana. Among them, Peirosauridae comprises medium-sized terrestrial predators widely distributed across southern continents during the Late Cretaceous. Here we describe a new peirosaurid crocodyliform, Antusuchus rionegrinus gen. et sp. nov., from the Cenomanian Candeleros Formation of the Neuqu & eacute;n Basin (R & iacute;o Negro Province, Argentina). The material, recovered from the La Buitrera Palaeontological Area, includes cranial and postcranial remains. Micro-computed tomography and anatomical comparisons reveal a unique combination of characters, including a short rostrum, an elongated palatal depression adjacent to the maxillary tooth row, a rod-shaped jugal bar, and a prominent sagittal crest. The dentition is ziphodont and includes a hypertrophied third maxillary tooth, consistent with predatory habits. Phylogenetic analyses recover Antusuchus rionegrinus as the earliest-branching member of Peirosauridae, sister to all remaining peirosaurids. This discovery provides new insights into the early evolution of peirosaurids and highlights the importance of the La Buitrera fauna for understanding mid-Cretaceous terrestrial ecosystems and the diversification of notosuchian crocodyliforms.
The reproductive organs from the Laguna Colorada Formation, Santa Cruz Province, Argentina, are identified and described as a megasporangiate strobilus assigned to Fredlindia sp. cf. F. fontifructus, and seeds of Fraxinopsis andium and Cordaicarpus mackayi. Associations between the fertile and vegetative organs are established, and the corresponding palaeogeographic distribution of these fossil assemblage is presented. According to co-occurrence data from various Triassic Gondwanan formations and comparative morphological analysis, Fredlindia sp. cf. F. fontifructus is associated with the leaves of Pseudoctenis multilineatum (Bennettitopsida), Fraxinopsis andium with the leaves of Yabeiella mareyesiaca and Y. wielandii (Gnetopsida), and Cordaicarpus mackayi with the leaves of Linguifolium lillieanum (Incertae sedis). This last association provides new evidence in support of previous proposal. Fredlindia represents the first record of the genus in Argentina, following previous findings in South Africa and Australia. Both Fraxinopsis and Cordaicarpus constitute new records for the Triassic in Argentina and Gondwana. The new organ associations facilitate future whole plant reconstructions and will aid phylogenetic analyses. These results provide key insights into the evolution and palaeodiversity of gymnosperm plants in the Late Triassic, emphasising the importance of this period in understanding the reorganisation of ecosystems in Gondwana.
