Zonocypris berthoui, Piovesan & Melo & Cabral & Guzmán, 2022

Piovesan, Enelise Katia, Melo, Gustavo Dias, Cabral, Maria Cristina & Guzmán, Juliana, 2022, New Early Cretaceous species of Zonocypris G. W. Müller, 1898 (Crustacea: Ostracoda) from the Crato Formation, Brazil, Zootaxa 5141 (6), pp. 581-591 : 584-586

Zonocypris berthoui sp. nov.

( Fig. 2 )

1994 Zonocypris sp. Berthou et al.: 541, pl. 1, figs 8–10.

1997 Zonocypris sp. Colin & Dépêche: 433, figs 2–14, 2–17.

ZooBank-link: urn:lsid:zoobank.org:act:879AA9BD-FBAA-4B02-945F-41844FAB3DE0

Etymology: In honor of the late Pierre-Yves Berthou, for his pioneering studies on ostracods of the Araripe Basin, including the first record of the species described herein.

Type-locality: Nova Olinda Municipality, Ceará State, Northeast Brazil.

Type-horizon: Late Aptian. Crato Formation, Santana Group , Araripe Basin, Brazil. Outcrop sample 1BAr17a, coordinates 7°06’52.3”S, 39°41’51.5”W .

Material: Four adult carapaces.

Holotype: LMA-00305, C, Adult female; L: 0.40 mm, H: 0.28 mm, W: 0.26 mm ( Figs 2A–F ). Outcrop sample 1BAr17a ( Três Irmãos Quarry ).

Paratypes: LMA-00331, C, Adult male, L: 0.42 mm, H: 0.28 mm. W: 0.27 mm ( Figs 2G–H ), 2-AR-SR-1A-CE well core sample from depth interval 124.55–124.58 m; LMA-00332, Adult female L: 0.42 mm, H: 0.22 mm, W: 0.31 mm ( Figs 2I–K ), 2-AR-SR-1A-CE well core sample from depth interval 121.05–121.09 m.

Repository: Collection of the Laboratório de Micropaleontologia Aplicada [Applied Micropaleontology Laboratory] ( LMA) from UFPE, Recife, Brazil.

Diagnosis: A species of Zonocypris with a small, sub-ovate to sub-triangular carapace in lateral view, with the typical ornamentation of thick, concentric ribs (except in the central area, where three sub-rectilinear ribs are present) containing abundant normal pore canals; intercostal areas narrow and smooth.

Description: Small carapace, sub-ovate to sub-triangular in lateral view; strongly tumid, with biconvex dorsal and ventral views. Valves slightly unequal, LV overlapping the RV on all sides. Greatest height located in anteromedian area, at anterior cardinal angle; height c. 2/3 of length in females. Greatest length below mid-height. Greatest width slightly posterior to mid-length, larger than half of length in females, smaller in males. Dorsal margin sub-rectilinear and short, ventral margin convex; anterior margin broadly rounded, posterior end infracurvate and subacute. Sexual dimorphism present, with female carapace more inflated in dorsal view, and male carapace more elongate and subtriangular laterally.

Surface entirely covered by coarse, sub-oval and regularly distributed concentric ribs, except in central area, where three sub-rectilinear ribs are present. In dorsal and ventral views, ribs are subparallel to major axis. Intercostal areas smooth and narrower than ribs. Abundant, round, simple normal pore canals (type A’ of Puri & Dickau 1969 and A1 of Danielopol et al. 2018) occur on ribs or adjacent to them throughout valve surface ( Figs 2I and K ). Some best preserve pores with very thin lip around hole, seen at high-resolution ( Figs 2F and J ), possibly belonging to the type A” of Puri & Dickau (1969) and A2 of Danielopol et al. (2018). Marginal pore canals also present, densely arranged ( Fig. 2E ).

Presence of microdenticles in anteroventral area only observed when carapace is disarticulated or broken in this zone ( Fig. 2K ). Other internal features not available.

Remarks: Normal pore canals and marginal pore canals are rarely referred to in the descriptions of Zonocypris species, probably because they both require high magnifications of SEM images to be clearly observed; moreover, many descriptions of Zonocypris species predated the widespread use of SEM, particularly those of recent species, where these small structures are easier to see. However, in recent publications with SEM images, the normal pore canals are often visible at high magnifications. We verified their presence in several fossil and extant species, always located on the ribs or adjacent to them; in Whatley et al. (2002) the presence of normal pore canals on the ribs of Zonocypris labyrinthicus Whatley, Bajpai & Srinivasan, 2002 was noted. The marginal pore canals are more difficult to observe. In Krstić (2006) there is a figure (Pl. LXVI, fig. 8) with the marginal pore canals of Zonocypris membranae quadricella Stancheva, 1966 ; the author described them as “long, thin and densely arranged”.

The presence of microdenticles in the RV is common in extant and sub-fossil species of Zonocypris . In the description of the extant Zonocypris cordata Sars, 1924 , from South Africa, the author refers to a “row of minute tubercles”, “both in front and behind” on the RV; microdenticles are also present in the anterior and posterior-ventral parts of the selvage of the RV of a very well preserved Holocene species from Mozambique (MCC observation on material from M. J. Martins, ICArEHB, Universidade do Algarve, Portugal, Project InMoz -PTDC/HAR-ARQ/28148/2017, ongoing studies); in the extant Zonocypris mardinensis Külköylüoðlu et al., 2021 , from Turkey, the presence of a row of fine denticles is referred to, but only in the posterior part of the calcified inner lamella of the RV (in the selvage, as we can see in fig. 4F, of Külköylüoðlu et al. 2021). The lack of descriptions of these structures in fossil species is probably due to the rarity of loose valves where they can be observed.

Zonocypris berthoui sp. nov. differs from other Early Cretaceous species of the genus mainly by its sub-triangular to ovoid outline and the ribs distribution pattern. Compared to Zonocypris ? expansa Tian & Zhao, 1982, from the Aptian-Albian of NE China, it is significantly smaller, with a very different lateral outline and thicker ribs. Zonocypris sp. recorded by Carignano et al. (2017) in the Barremian?–Aptian interval of Argentina has a rounded sub-trapezoidal outline in lateral view, a greatest width clearly in the posterior third and more asymmetrical arrangement of the concentric ribs in the center of the valve.

Some species from the Late Cretaceous resemble our proposed species. In India, Zonocypris labyrinthicus Whatley, Bajpai & Srinivasan, 2002 from the Maastrichtian of Mohagaonkala, and Zonocypris gujaratensis Bhandari & Colin, 1999 , from the Upper Maastrichtian-Base of Paleocene? of Anjar, Kachchh, Gujarat State, also show sexual dimorphism, but have a very small carapace with a more rounded lateral outline than Z. berthoui sp. nov.; moreover Z. labyrinthicus has RV>LV and lacks the ribs in the central part of the valves, and in Z. gujaratensis the greatest height is almost in the middle of the length. Zonocypris spirula Whatley & Bajpai, 2000 , from the Late Cretaceous and Paleogene of India, differs from the present species in having a very small carapace with spirally arranged ornament comprising a single helicoidal rib coiled on the valve surface. The Campanian Zonocypris digitalis Babinot, 2003 , from south-east France, presents a similar rib pattern, but differs in the truncated anterior and posterior margins, and in size, which is very small. The specimen of Zonocypris ? sp. from the Campanian–Early Maastrichtian? of Mali, figured in Colin et al. (1996), very likely belongs to the genus and shows similarities with Z. berthoui sp. nov., however it has an almost round outline and the intercostal areas are pitted.

Occurrence: Late Aptian, Crato Formation, Araripe Basin, Barbalha, Crato and Nova Olinda municipalities, Ceará State, Brazil ( Berthou et al. 1994; Colin & Dépêche 1997; this study).

Figures

FIGURE 2. Zonocypris berthoui sp. nov. (A–F) LMA-00305, holotype, female carapace, (A) general right view, (B) general left view, (C) general dorsal view; (D) general ventral view, (E) detail of D, showing normal and marginal pore canals, (F) detail of E, simple normal pore canals (type A” of Puri & Dickau 1969 and A2 of Danielopol et al. 2018); (G–H) LMA-00331, paratype 1, male carapace, (G) general dorsal view, (H) general left view; (I–K) LMA-00332, paratype 2, female carapace, (I) dorsal view, detail of anterior part, simple normal pore canals (type A’ of Puri & Dickau 1969 andA1 of Danielopol et al. 2018), (J) detail of I, simple normal pore canals (type A” of Puri & Dickau 1969 andA2 of Danielopol et al. 2018), (K) left view, detail of anteroventral denticulation.