New dinosaur tracksites from the Middle Jurassic of Madagascar: ichnotaxonomical, behavioural and palaeoenvironmental implications.

New dinosaur tracksites are described from the Bajocian-Bathonian Bemaraha Formation of western Madagascar. Two track-bearing surfaces can be followed over a distance of at least 4 km, suggesting the existence of a hitherto unrecognized megatracksite. The track assemblage is theropod dominated, but sauropod tracks also occur at one site. Qualitative and quantitative analysis of the abundant theropod track material suggests that most, if not all, theropod footprints are attributable to a single trackmaker and are referred to Kayentapus isp. Although this ichnogenus, originally described from the Lower Jurassic of North America, has never been recorded from Gondwana nor from the Middle Jurassic, track morphology strongly suggests this attribution. Palaeogeographical, sedimentological and ichnological data suggest that the dinosaur tracks formed in an intertidal to supratidal setting where the coastline influenced the preferred walking direction of the animals. [ABSTRACT FROM AUTHOR]