Centrocardita pileolata, P. G. Oliver & Holmes, 2004

Oliver, P. Graham & Holmes, Anna, 2004, Cryptic bivalves with descriptions of new species from the Rodrigues lagoon, Journal of Natural History 38 (23), pp. 3175-3227 : 3212-3213

publication ID	https://doi.org/ 10.1080/00222930410001695123
DOI	https://doi.org/10.5281/zenodo.5462220
persistent identifier	https://treatment.plazi.org/id/03B33A71-5612-FFAF-36D1-DEBE1640FA11
treatment provided by	Felipe
scientific name	Centrocardita pileolata
status	sp. nov.

Treatment

Centrocardita pileolata View in CoL n. sp.

( figures 124–128 View FIGS , 130, 131, 134 View FIGS )

HOLOTYPE: a live collected specimen (now disarticulated and rv gold-coated), RIBW RDS 52 , Grand Pate´ , off Port Mathurin, 19 ‡ 39.307 ’ S, 63 ‡ 24.950 ’ E, 29 September 2001, sand in surge channel, 17 m, scuba, coll. N. L. Bruce and J. Smith, NMW.Z.2001.061.00039.

PARATYPES: 2 lv (all gold-coated) and 6 rv, Grand Pate´, 18 m, NMW .Z.2001.061.00040.

Measurements (mm, L 6 H). Holotype: 2.90 6 2.56. Paratypes: 4.05 6 3.65, 3.13 6 2.17, 1.60 6 1.52, 1.25 6 1.17.

Description. Shell to 4 mm in length. Robust. Equivalve. Inequilateral, beaks about one-third distance from anterior. Outline trapezoidal anterior reduced; posterior dorsal margin long, straight, gently sloping to abrupt junction with truncated posterior margin, posterior ventral margin broadly rounded, ventral gently curved, anterior narrowly rounded, anterior dorsal straight and steeply sloping. Posterior area demarcated by a weak carina. Anterior and median sculpture of 13–14 strong, scaled ribs, those on the posterior carina most developed. Posterior area with a few weak riblets and a single strong rib close to the dorsal margin. Beaks prominent due to presence of a large projecting hat-like prodissoconch ( figures 127, 128 View FIGS ). Prodissoconch apex with an apical depression ( figure 128 View FIGS ) and strongly sculptured by irregular pitting ( figure 127 View FIGS ); merging into a smooth collar which is isolated from the dissoconch by a groove, in all with a diameter of 360 M m. Hinge strong. Left valve ( figure 128 View FIGS ) with two strong radiating cardinal teeth, a strong anterior lateral associated with a small ventral socket, and a denticulated dorsal area, posterior lateral longer than anterior with a deep dorsal socket. Right valve ( figure 134 View FIGS ) with a large median cardinal, anterior lateral projecting with a deep dorsal socket, posterior lateral as a marginal projection with denticulate surfaces. Inner margin deeply crenulate. External coloration white with sparse brown spots.

This species broods its young and embryos were found in the holotype ( figures 130, 131 View FIGS ).

Derivation of name. Latin pileolus diminutive of pileus ‘a cap’, referring to the form of the prodissoconch.

Comparisons. The only other carditid found on Rodrigues is referable to Cardita variegata (Bruguière, 1792) and in its juvenile stage has a less angular outline ( figures 129 View FIGS , 132 View FIGS ), a simple prodissoconch and a hinge with poorly developed lateral teeth ( figure 133 View FIGS ). Viader (1951) described two small carditids from Mauritius. Cardita vaughani is equilateral with the maximum height axis running through the umbo, not behind the umbo as in C. pileolata . Cardita vinsoni is inequilateral but the ribs are nodulose rather than scaly, the prodissoconch is not capped, and the carmine and brown coloration is not present in the Rodrigues shells. Many small carditids have been described from southern Africa and southern Australia and we have reviewed the relevant literature ( Bartsch, 1915; Turton, 1932; Barnard, 1964; Lamprell and Healy, 1998). Most of the smaller taxa are referred to Carditella but some to Centrocardita (s. g. Vimentum ) and most are equilateral. Carditella laticosta (Smith, 1904) ( South Africa) and C. (Vimentum) exulata ( Smith, 1885) (South Australia) have oblique outlines but have poorly ornamented ribs.