Amilnedwardsiidae

Püschel, Hans P., Shelley, Sarah L., Williamson, Thomas E., Perini, Fernando A., Wible, John R. & Brusatte, Stephen L., 2024, A new dentition-based phylogeny of Litopterna (Mammalia: Placentalia) and ‘ archaic’ South American ungulates, Zoological Journal of the Linnean Society 202 (1), pp. 1-50 : 16

Amilnedwardsiidae and the order Notopterna

Amilnedwardsiidae was proposed preliminarily by Soria (1984b) and better justified in a later article (Soria 1989a). It is based on two genera (i.e., Amilnedwarsia Ameghino, 1901 and Rutimeyeria Ameghino, 1901 ) and three species named after small bunodont isolated upper molars whose positions were assigned tentatively by Soria (1989a) by comparing them with the indaleciid Indalecia grandensis . Amilnedwardsiidae was considered to be the most basal family of the order Notopterna Soria, 1989 , which also includes the families Indaleciidae and Notonychopidae (Soria 1989b) . Notopterna is diagnosed by a well-developed and buccally projected parastyle and the absence of a mesostyle in the upper molars, bicrescentic and selenodont lower molars, and anteriorly acuminate petrosals, among other anatomical features that distinguish them from other SANUs (Soria 1989a). Soria (1989a, b) argued that, considering their dental similarities, ‘amilnedwarsids’ could be the structural ancestor of both indaleciids and notonychopids. However, a phylogenetic analysis failed to recover the members of Notopterna as a monophyletic group ( Bonaparte and Morales 1997), which has led to some authors to include its members tentatively within Litopterna (e.g., Gelfo et al. 2016, Croft et al. 2020, Goin et al. 2022). However, this is a problematic assumption as Bonaparte and Morales (1997) used a matrix that includes only litopterns, so the broader relationships of notopterns have not yet been tested in an analysis that includes other SANUs such as notoungulates and astrapotheres.

Amilnedwardia and Rutimeyeria were previously referred tentatively to the family Macraucheniidae and regarded as close to Victorlemoinea (Simpson 1945, 1948), although the latter now is now considered to be part of the family Sparnotheriodontidae . Cifelli (1983a)considered referred specimens of these taxa to be too fragmentary to determine a clear affinity,but suggested the referred specimens represent deciduous teeth of a henricosborniid notoungulate based on the presence of a metaconule-derived crest connecting with the ectoloph wall. Indeed, probably due to their limited fossil record, thus far no members of this family have ever been included in a phylogenetic analysis.

If we consider Amilnedwardsiidae to be a valid family, as its three species all come from Patagonian fossil localities of a similar age that correlate with the Vacan SALMA, the temporal interval of this family is ~45–42 Mya ( Fig. 2B; Supporting information, Table S1 ; Krause et al. 2017).