It’s hot and humid as usual in the Late Jurassic, so this Brontosaurus excelsus is cooling off by taking a dip in the river and spraying some water from its mouth onto its back (much like an elephant might spray water from its trunk). Sauropod dinosaurs like the Brontosaurus would have walked on land most of the time, but that doesn’t mean they wouldn’t have enjoyed wading through water every now and then.