In this article, I offer a contribution to the philological study of premodern materials of languages of South America that have already become extinct. I am concerned with the Yurumanguí language, whose speakers were encountered in the 18th century in the western lowlands of Colombia by a Spanish expedition. This encounter resulted in the production of a short collection of words and phrases by a priest which is analyzed here anew. Problems of inconsistent and likely highly inadequate orthographic representation of the speech of the Yurumanguí informants and other problems, in this case, make it highly difficult to arrive at consistent analyses, as I show throughout my highly tentative discussion of nominal and verbal morphosyntax. I also offer external comparisons for some of the available Yurumanguí lexical material. Far from being able to demonstrate the genetic connections of the language, such comparisons do allow to identify items the Yurumanguí language shared with neighboring languages and hence to situate it within the former linguistic ecology of this part of South America.