Leite et al.—Limnic Ostracoda from the Lower Cretaceous of Brazil
Description.—Small carapace, sub-squarish in lateral view, with height increasing evenly to the posterior margin, and greatest length at mid height. Left valve larger than right valve, overlapping all the margins of the carapace, with a well-marked overlap at the ventral region. Dorsal margin nearly straight to smoothly curvilinear, and ventral margin with a small concavity at the end of the first third of the carapace. Anterior margin sub- rounded and lower than the posterior margin. Posterior margin rounded. Smooth surface. In dorsal view, greatest width at the posterior end.
Materials.—Three levels from Tereza Farm, João Pinheiro, Minas Gerais State, southeastern Brazil: MP-3318, 50 car- apaces; MP-3428, 34 carapaces; MP-3436, 13 carapaces.
Remarks.—Considering that the type material for Darwinula martinsi Silva, 1978 is misplaced, this species was redescribed by Do Carmo et al. (2004b) based on neotypes from the type locality. Tomé et al. (2014) considered this species as a junior synonym for Alicenula leguminella (Forbes in Lyell, 1855). However, the material illustrated by Tomé et al. (2014) is dif- ferent from the material designated as neotype for Darwinula martinsi by Do Carmo et al. (2004b), due to the carapace con- tour, height/length ratio, and other diagnostic characteristics. Additionally, the specimens illustrated by Tomé et al. (2014) are different from Alicenula leguminella due to the anterior margin, which is slimmer, the posterior margin, which is wider, and the marked inclination of the ventral margin to the anterior margin.
Therefore, when reviewing the neotypes that once were identi- fied as Darwinula martinsi, it was verified that the species can be transferred to Penthesilenula martinsi (Silva, 1978). This reassignment to the genus Penthesilenula is based on the sub- quadrate shape in lateral view, a diagnostic characteristic that distinguishes it from Darwinula Brady and Robertson in Jones, 1885 emend. Pinto and Kotzian, 1961, associated with the height/length ratio ~0.5 (Ballent and Díaz, 2012). Such char- acteristics are observed in Darwinula martinsi, justifying the reassignment to Penthesilenula martinsi.
Penthesilenula pintoi new species Figure 6.4–6.6
Holotype.—A carapace (CP-871), length 0.680mm, height 0.310mm, width 0.240mm. Type level 23.57m from the base of the outcrop, Quiricó Formation, Areado Group, São Fran- cisco Basin, Lower Cretaceous, Aptian, from the banks of the São José River, São José Farm, Presidente Olegário munici- pality, Minas Gerais State, Brazil.
Paratypes.—Research Collection, Museum of Geosciences, Institute of Geosciences, Brasília, Brazil: carapace CP-875, length 0.730mm, height 0.320mm, width 0.320mm; carapace CP-894, length 0.680mm, height 0.300mm, width 0.250mm; carapace CP-895, length 0.680mm, height 0.310mm, width 0.220mm; carapace CP-896, length 0.680mm, height 0.300mm, width 0.210mm; carapace CP-897, length 0.660mm, height 0.290mm, width 0.200mm.
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Diagnosis.—Small carapace, oblong. Left valve larger than right valve. Dorsal margin smoothly curved, with well-marked inclination to the anterior margin. Ventral margin nearly straight with small concavity by the end of the first third. Anterior margin sub-rounded and low. Posterior margin rounded and broad.
Occurrence.—Brazil: Tereza Farm, João Pinheiro municipality and São José Farm, on the banks of the São José and Quiricó rivers, Minas Gerais State, southeastern Brazil, Quiricó For- mation, Areado Group, São Francisco Basin, Lower Cretaceous, Valanginian to Aptian.
Description.—Small carapace, sub-oval to sub-quadrate in lateral view, with height increasing evenly to the posterior margin, and greatest length at mid-height. Left valve larger than right valve, overlapping all the margins of the carapace. Dorsal margin nearly straight, inclined to the anterior margin, and ventral margin nearly straight, with small convexity anteriorly. Anterior margin sub-rounded and low. Posterior margin roun- ded and broader than the anterior one. Smooth surface. In dorsal view, width increasing evenly towards the posterior end.
Etymology.—In honor of Professor Ricardo Lourenço Pinto, Institute of Geosciences of the University of Brasília, for rich discussions on the Darwinulidae Family.
Materials.—Three levels from the São José creek, São José Farm, Presidente Olegário, Minas Gerais State, southeastern Brazil: MP-2884, four carapaces; MP-2895, 30 carapaces; MP-2960, 100 carapaces; one level from Quiricó creek, São José Farm, Presidente Olegário, Minas Gerais State, south- eastern Brazil: MP-3421, three carapaces; 22 levels from Tereza Farm, João Pinheiro, Minas Gerais State, southeastern Brazil: MP-3322, one carapace; MP-3323, four carapaces; MP-3325, three carapaces; MP-3326, 200 carapaces; MP-3327, 100 carapaces; MP-3328, two carapaces; MP-3333, one carapace; MP-3335, seven carapaces; MP-3340, 14 carapaces; MP-3427, three carapaces; MP-3428, 40 carapaces; MP-3429, 40 carapaces; MP-3431, 80 carapaces; MP-3433, six carapaces; MP-3434, 200 carapaces; MP-3436, 29 carapaces; MP-3437, 60 carapaces; MP-3438, two carapaces; MP-3439, 17 carapaces; MP-3442, 40 carapaces; MP-3443, 18 carapaces; MP-3448, two carapaces.
Remarks.—This species is more elongated and has the anterior margin broader than Penthesilenula martinsi (Silva, 1978). The taxonomic revision by Rossetti and Martens (1998) resulted in the description of three new genera, and a new diagnosis for Darwinula, whose right valve overlaps the left one, through the entire margin, except in the hinge region. Additionally, in lateral view, Darwinula is more elongated, with greatest height in the posterior quarter; posterior margin more broadly rounded than the anterior one; anterior margin narrower and slightly curved towards the ventral margin; ventral margin nearly straight, and dorsal margin curved. The genus Penthesilenula is sub-rectangular in lateral view, as discussed above. The closed carapaces herein studied did not allow observation of internal characteristics. However, due to its oval to sub-rectangular
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