Corbula, Bruguiere 1797

Arruda, Eliane P., 2020, Taxonomic revision of the recent marine Corbulidae (Mollusca, Bivalvia) from Brazil, Zootaxa 4851 (1), pp. 1-59 : 13-14

Genus CORBULA Bruguière 1797

Corbula Bruguière, 1797 : type species Corbula sulcata Lamarck, 1801 (subsequent designation Schmidt 1818); Recent, West Africa.

Aloidis Mergele von Mühlfeld, 1811 : Type species Aloidis guineensis Megerle von Mühlfeld, 1811 ; = Corbula sulcata Lamarck, 1811 .

Notocorbula Iredale, 1930 : type species Notocorbula vicaria Iredale, 1930 (original designation); = Corbula tunicata Hinds, 1843 .

Diagnosis. Shell inequivalve with right valve larger, higher, and more inflated and with grooved internal margins (like a gutter) to receive the left valve. Equilateral to inequilateral with a high keel between central and posterior slope; posterior slope elongates forming an acute rostrum. Umbos prosogyrate. Lunule area concave. Escutcheon well-defined by ridges on both valves. Right hinge plate with anterior cardinal tooth and posterior resilial socket, no chondrophore. Left hinge plate with anterior cardinal socket, and with chondrophore which becomes sunken and incorporated in hinge plate as shell grows older and becomes heavier; chondrophore with a tooth-like knob on the posterior region that becomes more evident and thicker as shell grows older.

Nepioconch (= pre-accretion shell) conspicuous with sculpture different from mesoconch. Sculpture of mesoconch with heavier commarginal ribs on the right valve and thinner on the left.

Remarks. According to Vokes (1945), the two recent genera of Corbulidae with a conspicuous nepioconch are Corbula and Notocorbula . Notocorbula was introduced for South Australian species with “cardinal tooth keeled” ( Iredale 1930, p. 404). Based on the description and figures of Notocorbula vicaria by Iredale (1930), “cardinal tooth keeled” seems to be a cardinal pyramidal tooth with a strongly dorsally curved apex and a shape like a keel when viewed from the dorsal face.

This type of cardinal tooth is common in many species of Corbulidae such as Corbula patagonica and species from other genera not considered by Vokes (1945), such as Juliacorbula bicarinata and Caryocorbula chittyana . Vokes (1945) accepted the genus Notocorbula “since the type figured by Iredale differs in a number of characters from the type of Corbula ” ( Vokes 1945, p. 14) but did not indicate these characters. However, morphological similarities between Corbula sulcata , species of Notocorbula from Southern Australia, described by Iredale (1945), as well as C. patagonica and C. tryoni from South America suggest that these species are closely related. For this reason, I presently treat Notocorbula as a junior synonym of Corbula .

According to Goodwin et al. (2008) Corbula species have a GF3 growth pattern with a conspicuous nepioconch whose ornamentation is different from the mesoconch. The species analyzed in the present work agree with this pattern. In Corbula species, the pre-accretion shell corresponds to the nepioconch of the specimens in their post-accretion stage.