Abstract The Natural History Museum (NHMUK) fossil reptile collections contain a set of specimens sent to Arthur Smith Woodward in 1908 by the Argentinian palaeontologist, Florentino Ameghino. This collection includes a skull and other material of Cricosaurus , a metriorhynchid thalattosuchian (or ‘sea crocodile’), a group of marine crocodylomorphs that existed from at least the Middle Jurassic to the Early Cretaceous. Handwritten labels in Spanish, probably by Ameghino, and notes in English signed by Smith Woodward are still with the specimens. Using Ameghino and Smith Woodward’s correspondence to investigate the history of the specimens, we have determined that they came from the Vaca Muerta Formation of the Neuquén Basin in Patagonia, they were in the fossil collection of the Museo Nacional, Buenos Aires (MNBA) and that Ameghino loaned them to Smith Woodward for a study that was never published. Therefore, they will be returned to Museo Argentino de Ciencias Naturales ‘Bernardino Rivadavia’, Buenos Aires. These fossils, although not the most impressive, are probably the first metriorhynchid material collected in South America.

Abstract Joaquín Frenguelli was born in Rome, Italy in 1883 and died in Santa Fe, Argentina in 1958. After receiving his PhD in medicine from Rome University, he moved to Argentina in 1911 and worked as a medical doctor in the cities of Santa Fe and Córdoba until 1929. From 1920 until 1933 he was a professor of geology at the Littoral National University. In 1934 he moved to La Plata, where he was director of the Museum of Natural Sciences (1935–46). The scientific work of Frenguelli is characterized by its scope and excellence and its main focus was on the Late Cenozoic. Frenguelli modified the chronology of the stratigraphic scheme of the Pampas region, proposed a relationship with climatic episodes and then expanded it, directly or indirectly, to the whole record of the Late Cenozoic in Argentina. His contributions on diatoms and other microscopic organic remains, as well as on fossil vertebrates and invertebrates, were related to the environmental setting of the Late Cenozoic. In the 1940s, Frenguelli also worked on the fossil plants of the continental Upper Palaeozoic and Early Mesozoic rocks of Argentina. As a result, he characterized the Triassic successions, introducing new stratigraphic units and discussing their relationships and chronology.