Excavation work began in the garden in the city of Pombal in 2017, when the owner of the property noticed fragments of fossilised bone and contacted researchers from the University of Lisbon.
Earlier this month, Spanish and Portuguese palaeontologists working at the site began unearthing the vertebrae and ribs of what they think is a brachiosaurid sauropod.
Sauropods were the biggest of all dinosaurs and the largest land animals ever to have lived.
The sauropod group – which includes the brontosaurus and diplodocus – were herbivores, had long necks and walked on four legs.
The size of the bones found in the garden suggests that the dinosaur was 12 metres high and 25 metres long.
Because of the natural position that the skeleton was found in, researchers are hopeful that further excavation may uncover more parts of the same dinosaur.
The skeleton was found in Upper Jurassic sedimentary rocks, suggesting it is about 150m years old.
According to theguardian