Tridactyl dinosaur footprints from the Triassic Sambaíba formation of northern Brazil

Some new tridactyl footprints have been recorded in the Malhada Vermelha farm locality, municipality of Fortaleza dos Nogueiras, state of Maranhão, northern Brazil, from the Sambaíba Formation, Parnaíba Sedimentary Basin. The specimens are fifteen isolated, in situ, mesaxonic tridactyl tracks preserved in six sandstone slabs as concave epireliefs. Abundant MISS evidence is preserved in the track-bearing blocks. The footprints are referred to as Grallator isp., linking them with an theropodian origin. The footprint-bearing levels were accumulated in shallow environments influenced by a tidal flat. The occurrence and interpretation of these findings bring a new approach to sedimentary subenvironments in the Sambaíba Formation. •Ichnofossils consisting of tridactyl footprints were found in the Sambaíba Formation, attributed to sedimentation in an arid climate.•All the track-bearing surfaces in the slabs or blocks have abundant evidence of microbially induced sedimentary structures.•The general features of the tracks presented herein allow to link their producer with Theropoda.•The analysis of the Sambaíba Sandstone outcropping in the study area allows us to consider the occurrence of marine incursions in that region of the basin during the late Triassic and early Jurassic.