Centrocardita pileolata Oliver & Holmes, 2004, n. sp.
Creators: name: Oliver, P. Graham
name: Holmes, Anna
Publisher: name: Zenodo
Year: 2004
Subjects: Biodiversity
Taxonomy
Animalia
Mollusca
Bivalvia
Carditida
Carditidae
Centrocardita
Centrocardita pileolata

description: Centrocardita pileolata n. sp.   
(figures 124–128, 130, 131, 134)  
 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). Prodissoconch apex with an apical depression (figure 128) and strongly sculptured by irregular pitting (figure 127); 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) 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) 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).  
 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, 132), a simple prodissoconch and a hinge with poorly developed lateral teeth (figure 133). 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.
description: Published as part of Oliver, P. Graham & Holmes, Anna, 2004, Cryptic bivalves with descriptions of new species from the Rodrigues lagoon, pp. 3175-3227 in Journal of Natural History 38 (23) on pages 3212-3213, DOI: 10.1080/00222930410001695123, http://zenodo.org/record/10097787