Brontosaurus ( ), meaning "thunder lizard" (from Greek βροντή, brontē = thunder + σαυρος, sauros = lizard), is a genus of sauropod dinosaurs. Originally named by its discoverer Othniel Charles Marsh in 1879, Brontosaurus had long been considered a junior synonym of Apatosaurus; its original species Brontosaurus excelsus having been reclassified as A. excelsus in 1903. However, an extensive study published in 2015 by a joint research team of England and Portugal concluded that Brontosaurus was a valid genus of sauropod distinct from Apatosaurus. Nevertheless, not all paleontologists agree with this division.