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 Recent palaeohistological studies on paramedian osteoderms of aetosaurs revealed the presence of growth lines (lines of arrested growth or LAGs) and a minimal or nonexistent secondary remodelling in the bone matrix of these elements. This feature allows the age of individuals to be estimated through growth line count. In the present contribution we study the growth curve of the South American aetosaur Aetosauroides scagliai . We estimated the age (obtained from LAG counting) and body size (body length and body mass were used as proxies) of different aetosaur specimens in order to reconstruct the growth curve of the South American species. The data obtained for Aetosauroides scagliai were compared with that of other aetosaurs, such as Neoaetosauroides engaeus , Aetosaurus ferratus , Aetobarbakinoides brasiliensis , Typothorax coccinarum and Paratypothorax sp. Our results indicate that, if body length is considered as proxy, all studied aetosaur specimens have a similar or almost identical growth rate. However, important variations arose among aetosaur taxa if body mass is considered as proxy, which would be related to a body morphology ranging from slender (e.g. Aetobarbakinoides brasiliensis ) to very wide ( Typothorax coccinarum ) morphotypes. In comparison with extant pseudosuchians (i.e. crocodylians), Aetosauroides scagliai possesses a relatively lower growth rate.