Indaleciidae (Bond & Vucetich, 1983)

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 : 16-18

Indaleciidae ( Figs 6A, 7A)

Indaleciidae currently includes three accepted genera with an exclusive Palaeogene distribution ( Fig. 2; Supporting information, Table S1 ). Indaleciidae was initially proposed by Soria (1984a) and better justified in a later article (Soria 1989a), in which he elevated the rank of the previously proposed subfamily Indaleciinae , which included Indalecia grandensis and Adiantoides leali ( Bond and Vucetich 1983) . Previously, A. leali from Divisadero Largo Formation, Argentina (age uncertain; Cerdeño et al. 2008, Woodburne et al. 2014a, López 2010), was placed tentatively in Adianthidae based on dental similarities with the adianthid Adianthus (Simpson and Minoprio 1949, Simpson et al. 1962). Later, Bond and Vucetich (1983) described Indalecia grandensis from the Lumbrera Formation, Argentina [Early Eocene ( Fernicola et al. 2021)], that showed dental similarities with Adiantoides leali , such as a buccolingually transverse crest connecting the hypocone with the metaconule, and the absence of a postprotocrista connecting the protocone with the metaconule on M1–M2, among other features that justified the proposal of a subfamily Indaleciinae within Adianthidae . Cifelli and Soria (1983a) tentatively followed Bond and Vucetich (1983) considering the shared presence of fossettes formed by hypertrophied conular cristae in the upper molars in members of Indaleciinae and typical adianthids. However, they also noticed some important features that separated them, such as the lack of a mesostyle on the upper molars and the lack of an entolophid (hypolophid in our matrix nomenclature; Fig. 3) on the lower molars, among other features. Cifelli and Soria (1983a) also added a new species Adiantoides magnus from Cañadon Vaca, Argentina, to Indaleciinae . The differences between indaleciines and adianthids and also the dental similarities of the former with ‘amilnedwarsiids’, led Soria (1989a) to propose elevating the subfamily Indaleciinae to the family Indaleciidae , including indaleciids, ‘amilnedwarsiids’, and notonychopids under the same order Notopterna (see Amilnedwardsidae and the order Notopterna section). Apart from some common dental features, indaleciids share features of the ear region with notonychopids, such as anteriorly acuminate petrosals; however, they diverge in the presence of enamel fossettes in the P2– M3 and less developed parastyles in indaleciids, among other dental features (Soria 1989b).

Cifelli (1993) conducted a phylogenetic analysis that included indaleciids (i.e., Indalecia and Adiantoides ) in a sample of different litoptern families and didolodontids, and found them to form a monophyletic group closely related to sparnotheriodontids (i.e., Victorlemoinea ), and these three taxa together were sister to didolodontids ( Fig. 1C). This result was probably influenced by Cifelli’s (1983b) indirect assignment of tarsals for Victorlemoinea (see Sparnotheriodontidae section). When Bonaparte and Morales (1997) repeated the analysis removing didolodontids and adding notonychopids, they similarly found this close relationship between indaleciids and sparnotheriodontids, without a close relationship with notonychopids ( Fig. 1D). However, in a different analysis based only on lower molars, Gelfo et al. (2008) found indaleciids in a polytomy with Notonychops powelli , and this polytomy as sister of the sparnotheriodontid Sparnotheriodon . Most authors since then have included Indaleciidae as a family of Litopterna (e.g., Croft et al. 2020). Nevertheless, a preliminary study that included ear region characters among other craniodental characters found the indaleciid Indalecia as a sister taxon to astrapotheres and notoungulates, instead of having a close relationship with Litopterna ( García-López and Babot 2014) . More recently, in a study that included litopterns, kollpanines, and didolodontids, the indaleciid Adiantoides was found at the stem of litopterns, being more closely related to them than to didolodontids ( Kramarz et al. 2021). In a different study that also included some early notoungulates, the indaleciid Indalecia was found in a polytomy that includes sparnotheriodontids, protolipternids, didolodontids, and North American phenacodontids (Zimicz et al. 2022). It is important to mention that most of these studies have a relatively limited taxon and character sample, and none of them have included members of all the litoptern families and early members of the various SANU orders ( Table 2 ). Therefore, including Indaleciidae within the order Litopterna can only be considered as tentative.

The earliest member of Indaleciidae is the Early Eocene Indalecia grandensis from the Lumbrera Formation, Argentina (55.0–46.2 Mya; Fernicola et al. 2021) and the youngest would be an undescribed indaleciid from the Abanico Formation, Chile (Wyss et al. 1994), which gives the family a temporal interval of 55.0–~31.5 Mya ( Fig. 2B; Supporting information, Table S1 ; Flynn et al. 2003, Fernicola et al. 2021).