Guaicurian
Guaicurian was a language isolate once spoken in Mexico.
An isolate: no relationship to any other known language has been demonstrated.
Waikuri (Guaycura, Waicura) is an extinct language of southern Baja California spoken by the Waikuri or Guaycura people. The Jesuit priest Johann Jakob Baegert documented words, sentences and texts in the language between 1751 and 1768.
Waikuri may be, along with the Yukian and Chumashan languages and other languages of southern Baja such as Pericú, among the oldest languages established in California, before the arrival of speakers of Penutian, Uto-Aztecan, and perhaps even Hokan languages. All are spoken in areas with long-established populations of a distinct physical type.
From Wikipedia · Waikuri language · CC BY-SA 4.0