One of the most delightful palaeontologists to grace our Earth was José Fernando Bonaparte (14 June 1928 – 18 February 2020). He was an Argentinian paleontologist who you'll know as the discoverer of some of Argentina's iconic dinosaurs — Carnotaurus (the "Bull" dinosaur we've talked about in a previous episode), along with Amargasaurus, Abelisaurus, Argentinosaurus and Noasaurus. His first love was mammals and over the course of his career, he unearthed the remains of some of the first South American fossil mammals from the Mesozoic. 
Between 1975 and 1977, Bonaparte worked on excavation of the Saltasaurus dinosaur with Martín Vince and Juan C. Leal at the Estancia "El Brete."  Bonaparte was interested in the anatomy of Saltasaurus, particularly the armored plates or osteoderms embedded in its skin. Based on this discovery, together with twenty examples of Kritosaurus australis and a lambeosaurine dinosaur found in South America, Bonaparte hypothesized that there had been a large-scale migration of species between the Americas at the end of the Mesozoic period.
The supercontinent of Pangea split into Laurasia in the north and Gondwana in the south during the Jurassic. During the Cretaceous, South America pulled away from the rest of Gondwana. The division caused a divergence between northern biota and the southern biota, and the southern animals appear strange to those used to the more northerly fauna. Bonaparte's finds illustrate this divergence. His work is honoured in his moniker given to him by paleontologist Robert Bakker — "Master of the Mesozoic"