Defining the Bemaraha megatracksite: an update on dinosaur ichnology in Madagascar

Abstract

Abstract The Bemaraha Formation preserves a unique and abundant record of dinosaur footprints, the only occurrence of this type known from Madagascar. Theropod and sauropod tracks occur in Middle Jurassic strata and form an important record from this otherwise poorly documented time interval. Here we report on 18 new tracksites, raising the total number of known localities in the Bemaraha to 31. The majority of these sites occur at the same stratigraphic level that can be traced over an area of at least 30 km 2 , which makes it one of the most laterally extensive occurrences of dinosaur tracks on record in the Southern Hemisphere. Dinosaur tracks are restricted to a few bedding surfaces representing times of sea-level lowstand within a normally marine environment. Theropod tracks are by far more abundant than sauropod tracks and typically are orientated towards the palaeocoastline. This pattern is interpreted as evidence of a short-scale migration between feeding and resting grounds. The Bemaraha Formation thus allows a rare glimpse into dinosaur behaviour in a marginal-marine environment of Jurassic age.