Stilotherium dissimile, Ameghino, 1887

Beck, Robin M. D., Voss, Robert S. & Jansa, Sharon A., 2022, Craniodental Morphology And Phylogeny Of Marsupials, Bulletin of the American Museum of Natural History 2022 (457), pp. 1-353 : 320

† Stilotherium

SPECIES SCORED: † Stilotherium dissimile (type species).

GEOLOGICAL PROVENANCE OF SCORED SPECIMENS: Santa Cruz Formation, Santa Cruz Province, Argentina.

AGE OF SCORED SPECIMENS: The Santa Cruz Formation contains the type fauna of the Santacrucian SALMA, which is estimated to span about 16–18 Mya in the Atlantic coastal plain and about 14–19 Mya in the Andean foothills based on tephrochronology (Perkins et al., 2012).

ASSIGNED AGE RANGE: 19.000 –14.000 Mya.

REMARKS: † Stilotherium dissimile is represented by abundant dental specimens from the Santa Cruz Formation, which we used to score this taxon. Unfortunately, well-preserved cranial material is as yet unknown. Specimens of † S. dissimile (including some material originally referred to “ Garzonia ” and “ Halmarhipus ”; see Marshall, 1980; Abello, 2007) have played a key role in discussions regarding antemolar homologies in paucituberculatans (e.g., Sinclair, 1906: 417; Osgood, 1921: 112–116; Ride, 1962; Marshall, 1980: 113–114; Abello, 2007, 2013). † Stilotherium is currently classified as a member of the extant paucituberculatan family Caenolestidae , within the superfamily Caenolestoidea (e.g., Abello, 2007, 2013; Goin et al., 2009a: table 3; Rincón et al., 2015; Abello et al., 2020: fig. 2), and published phylogenetic analyses consistently support a close relationship between † Stilotherium (and another fossil taxon, † Pliolestes ) and extant caenolestids (Goin et al., 2007, 2009a; Abello, 2013; Forasiepi et al., 2013; Rincón et al., 2015; Engelman et al., 2016; Abello et al., 2020).