This paper traces the trade routes of South American fossil mammal bones in the 1830s, thus elaborating both local and intercontinental networks that ascribed new meanings to objects with little intrinsic value. It analyses the role of British consuls, natural-history dealers, administrative instructions and naturalists, who took the bones from the garbage pits of ranches outside Buenos Aires and delivered them into the hands of anatomists. For several years, the European debates on the anatomy of Megatherium were shaped by the (...) arrival in London of a small living mammal and the ideas and evidence received from Montevideo on the existence of huge fossil bony armours. These debates culminated late in 1838 in the creation of the extinct genus Glyptodon by Richard Owen as a result of the exchange of letters, objects and depictions, and a series of contingent events. Based on primary sources and South American scholarship, this paper aims to contribute to the current debates among historians of science about the mobility of knowledge, as well as presenting the condition that made Charles Darwin's work possible. (shrink)