The Cretaceous actinistian Mawsonia is represented by more than 360 dissociated, but well-preserved, bones obtained from the Areado Group in the Sanfranciscana Basin of Minas Gerais, Brazil. These are among the oldest records of Mawsonia (Berriasian, Lower Neocomian) and include previously undescribed or poorly known skeletal elements (e.g. splenial, dentary, autopalatine, zygals). The new material is referred to the type species, M. gigas. Morphological variation in the sample blurs some of the distinctions formerly drawn between nominal species of Mawsonia, and species level diversity in the genus is difficult to establish. Mawsonia ubangiensis, M. libyca, and M. brasiliensis are considered to be junior subjective synonyms of M. gigas. Mawsonia gigas probably appeared prior to the separation of S America and Africa and became widespread throughout much of western Gondwana (including parts of Africa), even surviving briefly on both continents following their separation. Mawsonia tegamensis is a morphologically distinctive Late Cretaceous African species with no evident fossil record in Brazil and which probably arose by vicariant speciation following isolation of a local Mawsonia population during the later stages of rifting between Northern Africa and the rest of Western Gondwana. Similarities between Axelrodichthys, Lualabaea (here regarded as Early Cretaceous in age) and recently described fossils from Morocco, Niger, and Madagascar suggest the presence of a second endemic Cretaceous mawsoniid lineage in northeastern Brazil and Africa.

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