Vertebrate footprints and burrows from the Upper Jurassic of Brazil and Uruguay

The Upper Jurassic Guará Formation (Brazil) or Batoví Member of the Tacuarembó Formation (Uruguay) crops out to the south of the Paraná Basin. This unit is composed of fi ne to coarse-grained sandstones and rare mudstones which represent fl uvial and eolian depositional systems. The eolian facies of the Guará Formation (Late Jurassic) reveal footprints and trackways of vertebrates (dinosaurs), as well as burrows made by small vertebrates. Dinoturbated levels occur in eolian sand sheets of both Guará Formation and Batoví Member. All footprints and trackways are preserved in eolian dunes, sand sheets and interdune deposits. The Upper Jurassic Guará/Tacuarembó Formation contains numerous dinosaur tracks, dominated by theropod and sauropod tracks together with different vertebrate burrows. The occurrence of sauropod trackways with different gauge patterns in the same outcrop is unusual and suggests that this group formed herds that inhabited wet eolian sand sheets in the south of the Paraná Basin during the Late Jurassic. The size and shape of the burrows are compatible with excavations of therapsids, based on similar therapsid burrows found in South Africa and Antarctica. These burrows are likely to represent a permanent shelter used for dwelling and breeding. Only one burrow is smaller and subvertical, with a high “J” angle, probably produced by a very small mammal, similar to a rodent.