Leite et al.—Limnic Ostracoda from the Lower Cretaceous of Brazil
Occurrence.—Brazil: Recôncavo Basin, São Sebastião Forma- tion, Lower Cretaceous (Krömmelbein and Weber, 1971; Poropat and Colin, 2012a), Barremian (Silva et al., 2007). São Francisco basin, Quiricó Formation, Lower Cretaceous, Valanginian.
Description.—Medium-size carapace, sub-rectangular in lateral view, with greatest height anteriorly, and greatest length along mid-height. Right valve larger than left valve, overlapping the anterior, posterior, and ventral margins of the carapace. Dorsal margin nearly straight, with inconspicuous hump anteriorly; ventral margin nearly straight, sub-parallel to the dorsal margin. Anterior margin rounded; posterior margin sub-rounded. Reti- culated ornamentation all through the carapace. May exhibit nodules along the surface of the carapace, a smaller number of nodules, or complete absence of them. When present, nodules are in the ocular region, dorsally to medianly, and smaller ones scattered. Normal porecanals present in eye region, rounded. In dorsal view, larger nodules are evident, with greatest width posteriorly to mid-length.
Materials.—Four levels from Tereza Farm, João Pinheiro, Minas Gerais State, southeastern Brazil: MP-3324, two car- apaces; MP-3326, four carapaces; MP-3431, one carapace; MP-3434, 25 carapaces.
Remarks.—Due to the presence of specimens with and without nodules, it is necessary to propose a new diagnosis and description to Cypridea conjugata. Leite et al. (2016) discussed the similarity between specimens with and without nodules, in outline and in size, as well as valve relation. However, speci- mens with poorly developed nodules were not recovered. In the present work, such middle-ground specimens are recorded for the first time. Besides the small quantity, they always occur in specific regions of the carapace, and show marked normal por- ecanals. Do Carmo et al. (1999) suggested that the growth of nodules in Theriosynoecum kirtlingtonense Bate, 1965 indicates high salinity, caused by the reinforcement of the excretory sys- tem to maintain osmoregulation. In the same way, some por- ecanals in ostracodes are part of the excretory system, when present in nodule region, indicating that nodules are of pheno- typical origin as in Cyprideis torosa (Jones, 1850) (Do Carmo et al., 1999). In the present work, considering the good pre- servation, the presence of individuals with and without nodules, a new description and diagnosis are proposed, emended from Krömmelbein (1962).
Cypridea infima Krömmelbein and Weber, 1971 emend. Figure 5.8–5.13
1971 Cypridea infimaKrömmelbein andWeber, p. 71, pl. 1,fig. 3.
671
Holotype.—A carapace (BfB, type Nr. 7770) from the Candeias layers, lower and middle portions, Bahia State, Brazil (Kröm- melbein and Weber, 1971).
Diagnosis.—Very small carapace, with oval outline in lateral view. Reticulated surface, with normal porecanals throughout the carapace. Left valve with prominent angular projection in the posteroventral region.
Occurrence.—Brazil: Recôncavo Basin, Candeias Formation, lower and middle portions, Lower Cretaceous, (Krömmelbein and Weber, 1971; Poropat and Colin, 2012a), Berriasian– Valanginian (Silva et al., 2007); São Francisco Basin, Quiricó Formation, LowerCretaceous, Valanginian–Hauterivian/Aptian?
Description.—Very small carapace, sub-oval in lateral view, with greatest height antero-medianly, and greatest length in mid-height. Left valve larger than right valve, overlapping all the margins of the carapace, especially the ventral margin. Left valve with prominent angular projection in the posteroventral region. Dorsal margin convex, inclined posteriorly; ventral margin nearly straight to smoothly convex. Pronounced ventral beak and notch without exceeding the ventral margin. Anterior margin rounded. Posterior margin sub-rounded and smaller than the anterior one. Punctate ornamentation. Small nodules present throughout the carapace. Surface covered by very tiny rounded porecanals, also present in nodule region. In dorsal view, greatest width posteriorly.
Materials.—Nine levels from Tereza Farm, João Pinheiro, Minas Gerais State, southeastern Brazil: MP-3318, two car- apaces; MP-3322, three carapaces; MP-3427, five carapaces; MP-3428, five carapaces; MP-3431, three carapaces; MP-3433, two carapaces; MP-3434, three carapaces; MP-3444, two carapaces.
Remarks.—Krömmelbein and Weber (1971) described only the porecanals through the carapace. In the present work, the good preservation of material allowed observation of a punctate ornamentation, and that the porecanals are present along the carapace and in the small nodules. For this reason, a new description and diagnosis are herein presented, emended from Krömmelbein and Weber (1971).
Cypridea jequiensis Krömmelbein and Weber, 1971 Figure 5.14–5.16
1971 Cypridea jequiensis Krömmelbein and Weber, p. 75, pl. 3, fig. 11.
Figure 5. Species of the genus Cypridea Bosquet, 1852 and Neuquenocypris Musacchio, 1973, from the outcrop at Tereza Farm, João Pinheiro municipality, Minas Gerais State, southeastern Brazil. (1–7) Cypridea conjugata Krömmelbein and Weber, 1971 emend. (1–3) Adult with nodules (CP-863), right lateral view (RLV), left lateral view (LLV), and dorsal view (DV); (4, 5) adult without nodules (CP-864), right lateral view (RLV) and left lateral view (LLV); (6, 7) adult with nodules (CP-863), porecanals details. (8–13) Cypridea infima Krömmelbein and Weber, 1971 emend. (8–10) Adult (CP-867), right lateral view (RLV), left lateral view (LLV), and dorsal view (DV); (11–13) adult (CP-867), detail of the porecanals in nodule region and detail of porecanals on the surface of the carapace. (14–16) Cypridea jequiensis Krömmelbein and Weber, 1971, adult (CP-868), right lateral view (RLV), left lateral view (LLV), and dorsal view (DV). (17–19) Neuquenocypris (Protoneuquenocypris) antiqua Musacchio and Simeoni, 1991, adult (CP-869), right lateral view (RLV), left lateral view (LLV), and dorsal view (DV). (1–5, 14–19) Scale bars are 200 µm; (6, 7) scale bars are 5 µm; (8–10) scale bars are 100 µm; (11–13) scale bars are 20 µm.
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