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Journal of Paleontology 91(3):393–406


Figure 1. Simplified phylogenetic tree of protists, with examples of selected groups of testate amoebae having a significant fossil record shown on the right. (1) Cercozoa (possible euglyphid from near the top of the Ediacaran Bocaina Formation, Corumbá Group, Serra da Bodoquena, Brazil) (GP/5E 2544); (2) modern foraminiferan (https://depts.washington.edu/forams/order-lagenida/ genus-lagena/); (3) tintinnids from the Jurassic of Mexico (GP/5E-4280), and (4) vase-shaped microfossil interpreted as arcellinid (Tubulinea) (GP/5T-2529 F); (5) chitinozoan, an extinct group of uncertain affinity (https://commons.wikimedia. org/wiki/File:Whole_chitinozoan_cropped.jpg). Scale bars = 25µm(1), 50µm (2–4) and 10µm(5).


assigned to two taxonomic groups (Lahr et al., 2015): the Amoebozoa (e.g., arcellinids) and the Rhizaria (e.g., euglyphids and foraminiferans). The most extensive descriptions of Neoproterozoic VSMs


are from carbonaceous cherts, shales, and carbonate nodules in shales of the ~742±6Ma-oldChuarGroupof theGrandCanyon, USA (Bloeser, 1985; Karlstom et al., 2000; Porter and Knoll, 2000; Porter et al., 2003). Originally reported as chitinozoans (Bloeser et al., 1977), the Chuar VSMs are currently regarded as among the oldest fossil evidence not only of testate amoebae (Schopf, 1992, p. 588, 592; Parfrey et al., 2011; Fiz-Palacios et al., 2014), but of protists in general (Knoll, 2014; Butterfield, 2015) and of eukaryvory (Porter et al., 2003; Porter, 2011; Knoll, 2014; Strauss et al., 2014). Elaborating on the reported occurrences of VSMs listed by Porter and Knoll (2000), Strauss et al. (2014) tabulated the presence of vasiform microfossils, sensu lato, from more than two dozen Neoproterozoic units worldwide, part of which are illustrated in Figure 2. Of particular interest here are assemblages sharing species in common with the Chuar Group,


Figure 2. Geographic distribution of reported Neoproterozoic vasiform microfossils. References: Backlundtoppen Group—Svalbard (Knoll and Calder, 1983); Simla Slates—India (Nautiyal, 1978); Bonahaven Formation— Scotland (Anderson et al., 2013); Callison Lake Dolostone– Canada (Strauss et al., 2014); Chatkaragai Suite—Russia (Sergeev and Schopf, 2010); Chichkan Formation—Kazakhstan (Sergeev and Schopf, 2010); Chuar Group —USA (Porter et al., 2003); Dengying Formation (Ding et al., 1992; Duan et al., 1993; Zhang, 1994); Doushantuo Formation—China (Duan, 1985; Duan et al., 1993; Li et al., 2008); Draken Formation—Svalbard (Knoll et al., 1991); Elbobreen Formation—Svalbard (Knoll and Calder, 1983); Eleonore Bay Group—Greenland (Vidal, 1979; Green et al., 1988); Huaibei Group—China (Xiao et al., 2014); Rasthof Formation—Namibia (Bosak et al., 2011); Tanafjorden Group—Norway (Vidal and Siedlecka, 1983; Vidal and Moczydłowska, 1995); Togari Group—Tasmania (Saito et al., 1988; Turner et al., 1998); Tsagaan Oloom Formation—Mongolia (Bosak et al., 2011); Tindir Group—USA (Allison and Awramik, 1989; Macdonald et al., 2010); Upper Min’yar Formation—Russia (Maslov et al., 1994; Maslov, 2004); Uinta Mountain Group—USA (Dehler et al., 2010); Urucum Formation—Brazil (this paper); Vaishnodevi Limestone and Vindhyan Group—India (Maithy and Babu, 1988; Venkatachala and Kumar, 1998); and Visingsö Beds—Sweden (Knoll and Vidal, 1980).


known fromthe United States (PahrumpGroup,Horodyski, 1993; Corsetti et al., 2003; UintaMountain Group, Dehler et al., 2010), Canada (Callison Lake Dolostone, Strauss et al., 2014), Svalbard (Elbobreen Formation, Knoll and Calder, 1983; Backlundtoppen Formation, Knoll et al., 1989; Draken Formation, Knoll et al., 1991), and, with this and a previous report, Brazil (Urucum Formation, Fairchild et al., 1978; this paper). Other occurrences that are broadly similar but contain distinct taxa or taxa requiring further systematic study are known from Greenland (Eleonore Bay Group, Vidal, 1979; Green et al., 1988), Saudi Arabia (Jabal Rockham, Binda and Bokhari, 1980), Sweden (Visingsö Group, Ewetz, 1933; Knoll and Vidal, 1980; Vidal and Siedlecka, 1983; Martí Mus and Moczydłowska, 2000), China (Doushantuo Formation, Duan, 1985; Duan et al., 1993; Li et al., 2008; Dengying Formation, Zhang and Li, 1991; Ding et al., 1992; Duan et al., 1993; Zhang, 1994;HuaibeiGroup,Xiao et al., 2014), Kazakhstan (Chichkan Formation, Sergeev and Schopf, 2010), Russia (Chatkaragai Suite, Sergeev and Schopf, 2010), and Tasmania (Togari Group, Saito et al., 1988; Turner et al., 1998). Vasiform microfossils having distinctly differing morphology,


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