This led to months of meticulous digging, cleaning and classification of a large cache of bones: vertebrae as well as bits of rib, hip, tail and arm.
"When I lifted the vertebra and saw that it had the characteristics of a megaraptor, it was really a huge thrill," recalled Aranciaga.
"Somehow I fulfilled my childhood dream... finding a new fossil and it turning out to be a megaraptor: the group in which I specialize," he told AFP.
Maip was one of the last megaraptors to inhabit Earth before the dinosaurs went extinct about 66 million years ago, according to Fernando Novas of the Argentine Museum of Natural Sciences' Laboratory of Comparative Anatomy.
It is also the southernmost megaraptor ever found, added Aranciaga, a doctoral fellow at Argentina's National Scientific and Technical Research Council (Conicet).