Cranial endocast of Anagale gobiensis (Anagalidae) and its implications for early brain evolution in Euarchontoglires

Anagalids are an extinct group of primitive mammals from the Asian Palaeogene thought to be possible basal members of Glires. Anagalid material is rare, with only a handful of crania known. Here we describe the first virtual endocast of an anagalid, based on the holotype of Anagale gobiensis (AMNH 26079; late Eocene, China), which allows for comparison with published endocasts from fossil members of modern euarchontogliran lineages (i.e. primates, rodents, lagomorphs). The endocast displays traits often observed in fossorial mammals, such as relatively small petrosal lobules and a low neocortical ratio, which would be consistent with previous inferences about use of subterranean food sources based on heavy dental wear. In fact, Anagale gobiensis has the lowest neocortical ratio yet recorded for a euarchontogliran. This species was olfaction-driven, based on the relatively large olfactory bulbs and laterally expansive palaeocortex. The endocast supports previous inferences that relativel..., The endocast of Anagale gobiensis was generated from CT scan data of AMNH 26079.
The endocast of Anagale gobiensis (Fig. 3) is compared to the sample of previously published endocasts pertaining to early members of Euarchontoglires. In particular, the comparative sample includes early Glires, that is, “ischyromyids” (Paramys, Pseudotomus, Reithroparamys, Rapamys, and Ischyromys; Bertrand & Silcox, 2016; Bertrand et al., 2016a, 2019), fossil sciuroids (Bertrand et al., 2017, 2018), Rhombomylus (Meng et al., 2003) and a stem lagomorph (López-Torres et al., 2020); Primates, including “plesiadapiforms” (Silcox et al., 2009, 2010a; Orliac et al., 2014) and early Tertiary fossil euprimates (Kirk et al., 2014; Harrington et al., 2016, 2020; Ramdarshan and Orliac, 2016); and the most primitive apatemyid known from endocranial data (Labidolemur kayi; Silcox et al., 2011). A sample of extant rodents (Bertrand & Silcox, 2016; Bertrand et al., 2017, 2018, 2019) and extant lagomorphs (López-..., All files are submitted in .xlsx format, and are readable by Excel.