Mongolianella aptianensis, Tomé & Araripe & Oliveira & Barreto & Prado & Pedrosa & Pereira & Nascimento & Ng, 2022

Tomé, Maria Emilia, Araripe, Rilda, Oliveira, David, Barreto, Alcina, Prado, Ludmila, Pedrosa, Flavia, Pereira, Priscilla, Nascimento, Luiz Ricardo & Ng, Christiano, 2022, Early Cretaceous Ostracoda (Crustacea) from south-centralAraripe Basin, Brazil with descriptions of seven new species, Zootaxa 5159 (4), pp. 535-557 : 542

Mongolianella aptianensis sp. nov.

Fig. 3J–O

2021 Damonella grandiensis — Araripe et al., p. 6, fig. 5 (M–P).

2022 Mongolianella sp. —Araripe et al., p. 7, fig. 5 (7a–b).

Etymology: Aptian (lat.) derived from the range where this species was found.

Holotype: Adult carapace, Nº. DGEO-CTG-UFPE-1511 ( Fig. 3J–L ).

Paratype: Juvenile carapace, Nº. DGEO-CTG-UFPE-1512 ( Fig. 3M–O ).

Type locality: Brazil, State of Pernambuco, Municipality of Exu, Santo Antônio section. Coordinates 7° 30’ 06” S and 39° 32’ 36” W .

Type-horizon: Santo Antônio section, Araripe Basin. Shale (F1) corresponding to Romualdo Formation, depth 3.00m, dated as upper Aptian.

Dimension. Nº. DGEO-CTG-UFPE-1511 ( Fig. 3J–L ); L= (LV) 0.901 / ( RV) 0.979mm, H= 0.397mm, and W= 0.307mm.

Diagnosis: Large, smooth carapace with an outline that makes a sharp angle at the posteroventral margin.

Description. Carapace slightly concave in the central-ventral margin. Dorsal margin angular in the antero and posterodorsal portions in adults, while in juveniles the anterior angular portion promotes a strong fall to the anterior margin. In juveniles the posterodorsal cardinal angle is lower. Anterior margin rounded in both stages, unlike the posterior margin in adults, which is more rectangular, and in juveniles it is triangular. Maximum length at the ventral region. Maximum height at anterodorsal region, coinciding with the location of the cardinal angle. LV larger than RV with evident overlap along the central ventral margin, in juvenile specimens there is overlap along the dorsal margin, making the cardinal angle more prominent. In dorsal view, the greatest width is at the posterior margin, but narrower in the juvenile form. Smooth outer surface.

Observations. A very large and elongated species compared to the others of the genus. This species stands out for its size. First, it was considered that this species is of the marine genus Krithe Brady, Crosskey & Robertson, 1867 , but this genus is typical of deep waters, and so this idea was discarded. Detailed comparisons were also made with the species of Damonella described and deposited by Tome et al. (2014) and Araripe et al. (2021) in the Ivan de Medeiros Tinoco Microfossils Collection. The studied form is very large when compared to Damonella grandiensis Tomé et al., 2014 and Damonella ultima Tomé et al., 2014 . When compared, it presents the same characteristics of the species found by Araripe et al. (2021). It is worth noting that they are totally smooth specimens with a difficult level of identification, since they do not have ornamentation to use for comparisons. In the present study, we chose to call holotype Nº. DGEO-CTG-UFPE-1511 as an adult form and the paratype Nº. DGEO-CTG-UFPE-1512 as a young form, however further studies with a larger population would be necessary to recognise the male carapace and others ontogenetic stages.

Occurrence and associated fauna. It was recorded in the Santo Antônio section, at the following depths (from base to top): 1.8; 2.1; 2.25; 3.1; 3.4; 3.45; 3.55; 3.65; 3.85 and 4.05 m. Mongolianella aptianensis sp. nov. does not occur in association with Dicrorygma ( Orthorygma ?) dimorpha.

Stratigraphic distribution. Brazil, Araripe Basin, Romualdo Formation, upper Aptian.

Figures

FIGURE 3. (A–C) Pattersoncypris salitrensis (Krömmelbein & Weber, 1971); (A and B) nº DGEO-CTG-UFPE-1505, depth 2.65m, (A) right side view, (B) left side view; (C) nº DGEO-CTG-UFPE-1506, depth 3.55m, dorsal view. (D–F) Pattersoncypris angulata (Krömmelbein & Weber, 1971); nº DGEO-CTG-UFPE-1507, depth 2.65m, (D) right side view, (E) left side view, (F) dorsal view. (G–I) Pattersoncypris micropapillosa (Bate, 1972); (G) nº DGEO-CTG-UFPE-1508, depth 3.1m, right side view; (H) nº DGEO-CTG-UFPE-1509, depth 4.05m, left side view; (I) nº DGEO-CTG-UFPE-1510, depth 3.1m, dorsal view. (J-L) Mongolianella aptianensis sp. nov., nº DGEO-CTG-UFPE-1511, depth 3.1m; (J) right side view; (K) left side view; (L) dorsal view. (M–O) Mongolianella aptianensis sp. nov., juvenile carapace, nº DGEO-CTG-UFPE-1512, depth 3.1m; (M) right side view; (N) left side view; (O) dorsal view. (P–R) Damonella grandiensis Tomé et al., 2014; nº DGEO-CTG-UFPE-1513, depth 0.3m; (P) right side view; (Q) left side view; (R) dorsal view. The depth reference is from the bottom to the top. Scale bars are equivalent to 100µm.