Morais et al.—Neoproterozoic vase-shaped microfossils—Brazil
Etymology.—Limeta is Guarani (a major indigenous language in South America) for bottle.
Remarks.—The well-developed neck occupying 20–50% of the total specimen length differentiates this new genus and species from other formally VSM taxa, particularly Cycliocyrillium torquata Porter et al., 2003, whose neck does not exceed 10% of total test length.
Limeta lageniformis Morais, Fairchild, and Lahr, new species Figures 4.4, 6.7–6.9, 7.5, 7.6
Type material.—N = 10;HolotypeGP/5T: 2529 F (Figs. 4.4, 6.9). Paratypes (Fig. 6.7, 6.8, 7.5, 7.6) GP/5T: 2530 A, D; 2532 E; 2534 D; 2536 B, C, G, K; GP/5T: 2539 A, from the Neoproterozoic Urucum Formation, Jacadigo Group, Corumbá, Brazil (Repository: LPS, IGc-USP).
Diagnosis.—VSMs with tests consisting of a pyriform to subglobose body and a long neck, 20–50% the total length of the test, with a simple terminal aperture.
Description.—Total test length (L) = 100–133 µm; x = 115 µm;
σ = 11µm. W = 53–70µm, x = 63µm, σ = 5.6 µm. Circular aperture (AD = 12–32µm, x = 21µm; σ = 5 µm) at the termi- nus of a long, cylindrical neck (NL = 20–58µm; x = 40µm;
σ = 13µm). Body length (BL) = 56–89µm; aspect ratios calculated for total test length (L/W) 1.5–2(x = 1.8; σ = 0.17), but are considerably less (1.0–1.3) when just the body length (BL/W) is considered. Walls carbonaceous, uniformly thick (WT = 5–6 µm; x = 5.7 µm; σ = 0.58µm).
Etymology.—Lageniformis, from the Latin, lagena, bottle; and forma, shape.
Remarks.—At least four other long-necked Neoproterozoic microfossils have been illustrated in the paleontological litera- ture, but none qualifies for inclusion in L. lageniformis n. gen. n. sp. Knoll and Calder (1983, pl. 1, fig. 13) drew attention to a “long-necked” VSM in the Ryssö Formation, Svalbard. It is much larger than L. lageniformis n. gen. n. sp. (L = 260 µm), but its ‘long’ neck represents less than 10% of the total test length (NL = 19 µm) and its aspect ratio is much greater (2.6). Xiao et al. (2014, fig. 5B) recently presented a ferrous- oxide-lined mold having a neck nearly 60% the total length of the specimen within an assemblage of “possible vase-shaped microfossils” from the Jiayuan Formation (lower Huaibei Group) of China, of presumptive late Tonian (>716 Ma) age. But it, too, is large, more than twice the length (L = 320 µm) of the largest specimen of L. lageniformis n. gen. n. sp. (L = 133 µm), and has a much squatter body (aspect ratio, BL/W ≈ 0.8 versus 1.0–1.3). Battison and Brasier (2012, fig. 8D) illustrated an unnamed, similarly shaped organic-walled microfossil of smaller size from the Torridon Group (~1 Ga), Scotland, and pointed out its similarity to the acritarch Germinosphaera bispinosa Butterfield, 1994, described from the Svanbergfjellet Formation (700–750 Ma), Spitsbergen (in Butterfield et al., 1994, fig. 16.D, 16.E, 16.G). Both the single specimen from the Torridon Group (L = 50 µm;
401
BL = 30 µm) and G. bispinosa (BL = 13–35 µm) are much smaller than L. lageniformis n. gen. n. sp. (BL = 56–89 µm). Additionally, G. bispinosa may exhibit from one to four extremely long unobstructed processes that are very much narrower (3–5 µm) than the neck of L. lageniformis n. gen. n. sp. (12–32 µm).
Genus Taruma Morais, Fairchild, and Lahr, new genus
Type species.—Taruma rata n. gen. n. sp., by monotypy. Diagnosis.—As for type species, by monotypy.
Etymology.—Taruma is Guarani for an olive-shaped fruit; with reference to the shape of the internal chamber in the holotype.
Remarks.—The relatively short cylindrical body, rounded aborally and truncated at the apertural end, distinguishes this taxon from other VSMs.
Taruma rata Morais, Fairchild, and Lahr, new species Figures 4.3, 6.10–6.13, 6.14?
Type material.—N = 3; Holotype GP/5T 2533 B (Figs. 4.3, 6.10, 6.11); Paratype GP/5T 2538 A (Fig. 6.12, 6.13); from the Neoproterozoic Urucum Formation, Jacadigo Group, Corumbá, Brazil (Repository: LPS, IGc-USP). The specimen in Figure 6.14 (GP/5T-2536 D) is included in this species, but with reservations, as explained below.
Diagnosis.—VSMs with nearly cylindrical test having a roun- ded aboral end and a flat to low roof-like oral surface with a central narrow circular aperture.
Description.—Holotype (Figs. 4.3, 6.10–6.11) and paratype (Fig. 6.12, 6.13) share the diagnostic characters of the species and are similar in size and aperture diameter, the holotype measuring 94 µm (L) by 65 µm (W) with an aperture diameter of 21 µm, and the paratype, 91 µmby73 µm with an aperture diameter of 17 µm, which correspond to aspect ratios of 1.4 and 1.2, respectively. The oral pole in the holotype is flat and per- pendicular to the aboral axis and “roof-like” in the paratype due to the abrupt inward flexure of the walls at an angle of ~45o. The walls of both the holotype and the paratype are siliceous and are uniformly thick in the paratype (WT = 7 µm), but vary in the holotype from 11 µm at the aboral pole to 3 µm at midsection, thickening rapidly around the ellipsoidal internal cavity at the oral pole to 21 µm as measured in the apertural plane. In the holotype, EDS and Raman spectroscopy confirm the
presence of a thin organic coating on the inner side of the siliceous wall. The light brown pigment that colors the palimpsest fibrous texture lining the interior of the paratype (Fig. 6.12) may also be carbonaceous.
Etymology.—Rata from rátã, Guarani for hard; with reference to the reinforced aspect of the oral region in the holotype.
Remarks.—The two specimens assigned to Taruma rata n. gen. n. sp. conformprecisely to the species diagnosis and differ from
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