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Journal of Paleontology 92(4):661–680 Family Limnocytheridae Klie, 1938
Subfamily Timiriaseviinae Mandelstam, 1947 Genus Timiriasevia Mandelstam, 1947
Type species.—Timiriasevia epidermiformis Mandelstam, 1947.
Remarks.—The supra-subfamilial classification follows Liebau (2005). Sames (2009, 2011) is followed for subfamily and other categories. The genus Timiriasevia Mandelstam, 1947, common in Cretaceous limnic deposits worldwide, has not been docu- mented or recorded in Cretaceous sediments from the United States yet, however, it is found in Upper Jurassic sediments. This absence might result from misidentifications as Metacypris Brady and Robertson, 1870, due to the morphological simila- rities of young specimens of both genera (Sames, 2009, 2011). The genera Timiriasevia Mandelstam, 1947, Theriosynoecum Branson, 1936, and Metacypris Brady and Robertson, 1870 are members of the subfamily Timiriaseviinae, due to the presence of simple porecanals, and an evident egg pouch in females. The nonsulcate genera Gomphocythere Sars, 1924 and Timiriasevia Mandelstam, 1947, as well as some species of the monosulcate Metacypris Brady and Robertson, 1870, usually have some indication of sulcus, such as a wide and shallow depression, causing a lateral constriction anteriorly in dorsal view. Females of Timiriasevia and Metacypris differ in dorsal view. Metacy- pris has a cordiform shape, while Timiriasevia is elongated oval to piriform with a small lateral constriction anteriorly. More- over, Metacypris has a weak sulcus, which is absent in Timiriasevia.
Timiriasevia sanfranciscanensis new species Figure 6.10–6.16
Holotype.—A female carapace (CP-843), length 1.070mm, height 0.650mm, width 0.740mm. Type level at 90 cm from the base of the Quiricó Formation, Areado Group, São Francisco Basin, Lower Cretaceous, Valanginian, João Pinheiro munici- pality, Minas Gerais State, Brazil.
Paratype.—Research Collection, Museum of Geosciences, Institute of Geosciences, Brasília, Brazil, male carapace CP-874, length 1.010mm, height 0.600mm, width 0.600mm.
Diagnosis.—Oval carapace, rounded in lateral view. Left valve slightly larger than right valve, with overlap of the left valve over the right one, mainly in the anterior margin, and overlap of right over left valve in the posterior margin. Ventral margin straight. Surface covered by punctuations, more evident near the margin. In dorsal view, highly inflated and piriform.
Occurrence.—Tereza Farm, João Pinheiro municipality, Minas Gerais State, southeast Brazil, Quiricó Formation, Areado Group, São Francisco Basin, Lower Cretaceous, Valanginian.
Description.—Medium to large carapace, oval to rounded in lateral view, with greatest height at mid length, and greatest length ventral-medianly. Left valve slightly larger than right one, overlapping it mainly in the anterior margin; right valve
overlapping the left one in the posterior margin. Dorsal margin convex, inclined anteriorly; ventral margin straight, with a smooth inclination towards the anterior margin. Anterior margin sub-rounded. Posterior margin broadly rounded. Surface poorly punctuated, with ornamentation more evident near the margins, mainly in the ventral region. In dorsal view, strongly inflated and piriform, with subtle constriction anteriorly. In ventral view, broad and straight. Sexual dimorphism present: males with less- convex dorsal margin compared to the females, and narrower in dorsal view.
Etymology.—After the name of the basin wherein it was described.
Materials.—Four levels from Tereza Farm, João Pinheiro, Minas Gerais State, southeast Brazil: MP-3318, three carapaces; MP-3322, three carapaces; MP-3427, seven carapaces; MP-3433, one carapace.
Remarks.—The genus Timiriasevia, according to Sames (2009, 2011), has a rounded oblong shape in lateral view; in dorsal view, the females are piriform, with slight constriction ante- riorly; there are no sulci or nodules; the ornamentation can be concentrically striated, sometimes combined with punctuation.
Additionally, the recovered specimens have the ventral margin flattened and wide, in accordance to the Limnocytheridae. Timiriasevia sanfranciscana n. sp. is the first species of the genus Timiriasevia formally described in the Cretaceous deposits in Brazil.
Discussion
The species studied in the present work are important for future research on the geographic and stratigraphic distribution, as well as the correlation between Argentinian, African, and Brazilian continental and marginal basins. Aptian deposits of the marginal basins are important for oil exploration, since source rocks and/ or reservoirs are present in them. Additionally, the presence of species from the Valanginian, as well as from the Barremian– Aptian interval, can lead to a new age interpretation for the Quiricó Formation and, therefore, to a new interpretation for continental Cretaceous in Brazil. Of the 16 species identified for the Lower Cretaceous
from the São Francisco Basin, 13 occur in other basins from Brazil, Argentina, and Africa: Harbinia alta, Harbinia angulata, Harbinia crepata, Harbinia salitrensis, Harbinia symmetrica, Brasacypris fulfaroi, Brasacypris ovum, Cypridea conjugata, Cypridea hystrix, Cypridea infima, Cypridea jequiensis, Neuquenocypris (Protoneuquenocypris) antiqua, and Penthesilenula martinsi. In theGrajaúBasin:H. alta (upperAptian) andH. salitrensis
(Aptian) (Ramos et al., 2006; Do Carmo et al., 2008). In the Araripe Basin: H. alta and H. salitrensis, both from
the upper Aptian (Krömmelbein and Weber, 1971; Viana et al., 1989; Silva-Telles and Viana, 1990; Do Carmo et al., 2008; Poropat and Colin, 2012a; Antonietto et al., 2012; Tomé et al., 2014);H. symmetrica (Aptian) (Coimbra et al., 2002);H. crepata (Aptian) (Silva-Telles and Viana, 1990); P. martinsi (Aptian); H. angulata (Aptian) (Poropat and Colin, 2012a).
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