Gabonorygma sergipana, Antonietto & Carmo & Viviers & Neto & Hunt, 2016

Antonietto, Lucas Silveira, Carmo, Dermeval Aparecido do, Viviers, Marta Claudia, Neto, João Villar Queiroz & Hunt, Gene, 2016, Ostracoda (Arthropoda, Crustacea) from the Riachuelo Formation, Sergipe-Alagoas Basin, Brazil, Upper Aptian-Albian, European Journal of Taxonomy 244, pp. 1-57 : 29-32

Gabonorygma sergipana gen. et sp. nov.

urn:lsid:zoobank.org:act:185D3B61-6920-4DFA-89CA-260C37B43608

Fig. 7 I–R

“ Asciocythere” GA E 26 – Grosdidier 1979: 8, fig. 58a–c.

Ovocytheridea aff. reniformis van den Bold, 1964 – Viviers et al. 2000: 425, figs 14.3–14.4. Pattersoncypris ? sp. 1 – Piovesan et al. 2013: 244, fig. 4.3a–b.

Diagnosis

A species of Gabonorygma gen. nov. distinguished by the following features: carapace with greatest height at the antero-central region and greatest width at the centro-posterior region, round, slightly infra-curvate posterior end and weakly developed inner margin, not visible in the oral region, where the selvage bends inwards expressively.

Etymology

From Sergipe State, Brazil, where the species was described.

Type material

Holotype

BRAZIL: ♀, carapace, stored dry in a micropaleontological slide (CP-698).

Allotype

BRAZIL: ³, carapace, stored as the holotype (CP-699).

Paratypes

BRAZIL: ♀, carapace (CP-700), ♀, carapace (CP-701), ♀, valve (CP-702) and ³, carapace (CP-703); stored as the holotype.

Other material examined

BRAZIL: 1-US-1 well, Laranjeiras Municipality, Sergipe State (depths of 399, 450, 1011, 1020 and 1080 m); 7-CP-252 well, Santo Amaro das Brotas Municipality, Sergipe State (depth of 512.7 m); Fazenda Santa Bárbara outcrop, Rosário do Catete Municipality, Sergipe State (sample MP-1419), approximate coordinates 10°39' S, 37°01' W; Penha outcrop, Riachuelo Municipality, Sergipe State (samples MP-1450 to MP-1452 and MP-1459), approximate coordinates 10°42' S, 37°13' W; Porto dos Barcos 3 outcrop, Riachuelo Municipality, Sergipe State (samples MP-1460, MP-1461, MP-1463, MP-1465 and MP-1468 to MP-1472), approximate coordinates 10°43' S, 37°10' W; São José 1 outcrop, Riachuelo Municipality, Sergipe State (samples MP-1550 to MP-1565), approximate coordinates 10°44' S, 37°13' W.

Type locality and stratum

Sample MP-1472, Porto dos Barcos 3 outcrop, Riachuelo Municipality, Sergipe State, Brazil, approximate coordinates: 10°43' S, 37°10' W; Riachuelo Formation, Sergipe-Alagoas Basin, middle Albian, Aracajuia benderi zone (MSA-0), Praebythoceratina amsittenensis subzone (MSA-0.3).

Measurements

Holotype (CP-698): ♀, carapace: length = 0.40 mm, height = 0.23 mm, width = 0.21 mm. Allotype (CP-699): ³, carapace: length = 0.40 mm, height = 0.22 mm, width = 0.17 mm. Paratype (CP-700): ♀, carapace: length = 0.38 mm, height = 0.22 mm, width = 0.20 mm. Paratype (CP-701): ♀, carapace: length = 0.40 mm, height = 0.23 mm, width = 0.21 mm. Paratype (CP-702): ♀, left valve: length = 0.37 mm, height = 0.22 mm.

Paratype (CP-703): ³, carapace: length = 0.38 mm, height = 0.20 mm, width = 0.17 mm.

Description

In lateral view, sub-rounded to sub-rectangular carapace, with greatest height at antero-central and greatest length at central regions. Left valve larger than the right, slightly overlapping it at ventral margin and posterior end. Round anterior end, becoming slightly rectilinear close to dorsal margin, forming an obtuse cardinal angle. Round, slightly infra-curvate posterior end; obtuse posterior cardinal angle. Slightly rectilinear to concave dorsal margin. Rectilinear ventral margin. Smooth overall ornamentation. In dorsal view, elliptical, with greatest width at centro-posterior region. In internal view, adont hinge, composed of smooth bar in left valve. Weakly developed inner lamella, not visible in oral region, where valve margin bends inwards expressively. Selvage visible through entire free margin. Central muscle scar group consisting of at least three elliptical central scars oriented in its greatest axis from anteroventral to postero-dorsal margins and an elliptical frontal scar. Weak sexual dimorphism: females more sub-rounded and wider in dorsal view, males more sub-rectangular and narrower.

Remarks

Gabonorygma sergipana gen. et sp. nov. can be separated from Gabonorygma brotzeni by the more rounded shape of its posterior end, the more anterior position of its greatest height and the more central position of its greatest width. Specimens in Grosdidier et al. (1979), Piovesan et al. (2013) and Viviers et al. (2000) also belong to the new species.

Paleoecology and distribution

Gabonorygma sergipana gen. et sp. nov. is a marine, shelf species occurring in the following localities and stages: Madiéla Formation, Gabon Basin, Gabon, lower–middle Albian ( Grosdidier 1979). Angico ( Viviers et al. 2000) and Taquari (present work) Members, Riachuelo Formation, Sergipe-Alagoas Basin, uppermost Aptian–Albian, Aracajuia benderi (MSA-0) and Aracajuia antiqua (MSA-1) zones, Brazil.