Xibalbaonyx is an extinct genus of megalonychid ground sloth known from the Late Pleistocene of Mexico.

[2] The overlapping remains of the skull and mandibles have notable differences between them, enough to call them distinct species.

[3] In 2020, a description of the postcranial remains of the holotype X. oviceps was published[4] In 2021, remains of a form closely related to Xibalbaonyx was reported from the Pleistocene of Cueva de Iglesitas near Caracas, Venezuela.

[5] Xibalbaonyx oviceps was about 2 metres long and weighed about 200 kilograms,[4] with a similar weight suggested for X.

[3] The forearms of X. oviceps are well built and likely had well developed muscles, with the range of mobility of the limbs being high.