Caryocorbula lavalleana (d’Orbigny, 1853 in 1841–1853)

Figure 6

Corbula lavalleana d’Orbigny, 1853 (in 1841–1853): 284, pl. 27, fig. 9–12.

Corbula (Cuneocorbula) lavallena . Lamy, 1941: 231.

Corbula (Caryocorbula) tarasconii Arruda, Domaneschi, Francisco & Barros, 2007: 201–209, figs. 1–18.

Type material examined. Corbula lavalleana d’Orbigny, 1853 (in 1841–1853). BMNH 1854.10.4.551/1, lectotype designated herein, right valve, the specimen closest to the original length measurement; 6.2 mm length, 4.7 mm height, Jamaica (Fig. 6 A–B). BMNH 1854.10.4.551/2–22, paralectotype, 10 right valves and 11 left valves, Jamaica. The type lot also has one specimen in pre-accretion stage of Caryocorbula swiftiana (BMNH 1854.10.4.551/23) and 2 right valves and 4 left valves, probably specimens in pre-accretion stage of C. chittyana (BMNH 1854.10.4.551/24–29). The only known text and plate of Corbula lavalleana d’Orbigny were published in 1853 (in 1841–1853), in which there is no mention of a type. The lot BMNH 1854.10.4.551 of the Natural History Museum in London is registered as being the syntype lot purchased from d’Orbigny.

Corbula (Caryocorbula) tarasconii Arruda, Domaneschi, Francisco & Barros, 2007 . MZSP 84452, holotype (original designation), open pair, 7 mm length, 5 mm height, 4 mm width, off Guarapari municipality, Espírito Santo state, 20 o 45’S, 40 o 25’W, Brazil (Fig. 6 C–F). Paratypes, MZSP 84453, one pair; MZSP 84454 to 84461, 6 right, 2 left valves, northeast of Bahia state, 11 o 58.7’S, 36 o 49.2’W, 01.XI.2000; MZSP 84462 to 84464, 3 complete shells, 1 left valve, southeast of Bahia state to Guarapari Municipality, Espírito Santo state, 15 o 33’S, 38 o 56’W to 20° 45’S, 40° 25’W; MZSP 86026, one pair, northeast of Rio de Janeiro state, 21° 20’ 28”S, 40° 16’ 09”W; MNRJ 11146 to 11147, 2 pairs; MNRJ 11148 to 11157, 2 pairs, 5 right, 5 left valves, northeast of Bahia state, 11 o 58’ 07”S, 36 o 49’ 02”W; MNRJ 11040, 1 right, 1 left valve, southeast of Bahia state, 15 o 53’ 82”S, 38 o 31’ 09”W; MNRJ 11812, one pair, off Guarapari Municipality, Espírito Santo state, X.1992, 60– 70m ; MORG 50792, 4 pairs, off Boipeba Municipality, Bahia state, 13 o 35’ 18.33”S, 38 o 54’ 48.27”W ; MORG 50789, 7 pairs, 16 right, 19 left valves, off Camamu Municipality, Bahia state, 13 o 55’ 58.79”S, 38 o 05’ 28.13”W .

Diagnosis and Redescription. The description given by Arruda et al. (2007) is very complete and there is no need for supplementary information. Caryocorbula lavalleana does not present distinct nepioconch and the difference between specimens in pre-accretion stage and post-accretion stage indicates that this species has GF2 growth pattern.

Distribution. Caryocorbula lavalleana has been recorded from Cuba, Jamaica, Guadaloupe, Martinique (Rosenberg 2009) and Brazil. In Brazil, the analyzed specimens were colected from northeast of state of Bahia to northeast of state of Rio de Janeiro, from depths of 20 to 100 m.

Remarks. Part of the problem related to the identification of C. lavalleana is due to the mixture of species present in the type lot. In addition to shells of C. lavalleana, the type lot contains valves of C. swiftiana and probably valves of pre-accretion shell of C. chittyana . The largest specimen in the type lot belongs to C. chittyana with a length of 7.2 mm, which does not seem to be what was originally drawn and measured by d’Orbigny (6 mm in length). Although the original description does not consistently define the species, the figure is clear enough. After analyzing the type lot, I suggest considering Corbula taraconii as a synonym of C. lavalleana .

The Western Atlantic species most closely related to C. lavalleana are Juliacorbula aequivalvis, C. chittyana and C. swiftiana, and the latter had been considered a senior synonym of C. lavalleana (Mclean 1951; Rosenberg 2009). The differences between C. lavalleana and J. aequivalvis and C. swiftiana are well described in Arruda et al. (2007).

Caryocorbula lavalleana is also distinguished from thick shell specimens of C. chittyana by its short ventrally curving rostrum and straight posterior margin, while in C. chittyana the rostrum is moderately developed and aligned with the antero-posterior shell axis, and the posterior margin is sinuous. In addition, the surface of the valves in C. lavalleana is regularly convex, while in Caryocorbula chittyana it is irregular with two distinct phases of growth. Caryocorbula lavalleana is more similar to specimens in pre-accretion stage of C. chittyana . Caryocorbula lavalleana can be distinguished from pre-accretion shell of C. chittyana by its ventrally curving rostrum, commarginal ribs with the base about three times broader than the intercostal spaces, and by the hinge axis oblique to the antero-posterior shell axis. Specimens in pre-accretion stage of C. chittyana have a short rostrum and aligned with the antero-posterior shell axis, the valves are regularly convex, the base width of the commarginal ribs is narrower than the intercostal spaces, and the hinge axis is parallel to the antero-posterior shell axis (compare figures 5M–Q of specimens in pre-accretion stage of C. chittyana with figure 6 of C. lavalleana).

Caryocorbula lavalleana is also very similar to Caryocorbula marmorata (Hinds, 1843), and the characters that distinguish them are described below.