SPECIES SCORED: † Pichipilus osborni (type species), † P. centinelus, † P. riggsi.

GEOLOGICAL PROVENANCE OF SCORED SPECIMENS: Santa Cruz Formation, Santa Cruz Province, Argentina († Pichipilus osborni and † P. centinelus); Sarmiento Formation, Colué-Huapí Member, Gran Barranca, Chubut Province, Argentina († P. riggsi).

AGE OF SCORED SPECIMENS: Examined specimens of † Pichipilus osborni and † P. centinelus are from “Notohippidian” (“Notohippidense”) sites in the Santa Cruz Formation, which appear to represent the early part of the Santacrucian SALMA (about14–19 Mya; see † Stilotherium, above). By contrast, the Colué-Huapí fauna of the Sarmiento Formation, the type fauna of the Colhuehuapian SALMA and source of our material of † P. riggsi, is estimated to span the interval from 20.0 to 20.4 Mya (i.e., early Miocene) based on radiometric and magnetostratigraphic evidence (Ré et al., 2010).

ASSIGNED AGE RANGE: 20.400 –14.000 Mya.

REMARKS: The holotype and only known specimen of † Pichipilus centinelus, a partial cranium and associated partial left mandible (MLP- 68-I-17-204) described by Marshall and Pascual (1977; see also Goin et al., 2003, 2007b), is one of only a handful of fossil paucituberculatan skulls currently known. Conflicting opinions have been expressed as to whether this specimen preserves evidence of an anteorbital vacuity between the nasal, frontal, and maxillary bones, a distinctive cranial feature that is unique to caenolestids among extant marsupials (Thomas, 1895; Osgood, 1921, 1924; Bublitz, 1987; Patterson and Gallardo, 1987; Goin et al., 2003, 2007; Abello, 2007). Most of our character data for † Pichipilus is based on MLP-68-I-17-204. However, we also used specimens of † P. osborni (known only from the holotype, a partial mandible) and † P. riggsi for scoring dental characters (see Abello, 2007). † Pichipilus was referred by Goin et al. (2009a) to the family † Pichipilidae, which falls within the larger clade Palaeothentoidea in recent large-scale phylogenetic analyses of Paucituberculata (Abello, 2013; Rincón et al., 2015; Engelman et al., 2016; Abello et al., 2020).