Pectinoidea (Mollusca, Bivalvia, Propeamussiidae, Cyclochlamydidae n. fam., Entoliidae and Pectinidae) from the Vanuatu Archipelago

ABSTRACT This paper documents the species of Pectinoidea Rafinesque, 1815 collected in Vanuatu during the SANTO 2006 expedition. A total of 49 species (13 Propeamussiidae Abbott, 1954, 4 Cyclochlamydidae n. fam., 1 Entoliidae Teppner, 1922, and 31 Pectinidae Rafinesque, 1815) are represented, of which 70% are new records for Vanuatu. A new family, Cyclochlamydidae n. fam., is established for the genera Cyclochlamys Finlay, 1926, Chlamydella lredale, 1929 and Micropecten n. gen., formerly placed in Propeamussiidae, but differing by their sculptured prodissoconch (smooth in Propeamussiidae), an occasionally antimarginally sculptured right valve (smooth or weak commarginally sculptured in Propeamussiidae), a (common) simple outer prismatic layer of longitudinally hexagonal microstructure on the right valve (an outer layer of columnar calcite in Propeamussiidae). The family Cyclochlamydidae n. fam. includes about 30 species, all with adult size in the 1.2–6 mm range, and living mainly in the Southern Hemisphere and Indo-West Pacific; the family is not known from the Arctic, the Atlantic, or the northern and eastern Pacific. One new genus, Micropecten n. gen., and two new species, Cyclochlamys aperta n. sp. and Micropecten excuratus n. gen., n. sp., are described.


INTRODUCTION
Espiritu Santo is the largest island of Vanuatu (formerly known as the New Hebrides), situated in the north of the archipelago and, together with Malo and a few smaller satellite islands, forming the administrative province of Sanma. This paper deals with the littoral and bathyal pectinoid species collected during the expedition (Bouchet et al. 2011a. The expedition, based in Luganville, sampled the southeast corner of Santo Island and we refer to Bouchet et al. (2011b) for methods used in the field and samples and specimens workflow in the lab. An earlier paper  had reported on the deep-sea pectinoids sampled during the MUSORSTOM 8 expedition, but ironically the shallow-water fauna of the archipelago had earlier never been properly sampled.

Cyclopecten kapalae
reMArks This newly named family of micro-scallops includes three genera (Cyclochlamys, Chlamydella Iredale, 1929 and Micropecten n. gen.) formerly classified in Propeamussiidae. Cyclochlamydidae n. fam. comprises c. 30 Recent species mainly recorded from southern Australia, eastwards to New Zealand, but also recorded from the West Pacific (southern Japan and Indonesia), southwestern Indian Ocean (Rodrigues), and the Falkland Islands. It is absent in the Arctic, the Atlantic, and the northern and eastern Pacific.
Cyclochlamydidae n. fam. differs from Propeamussiidae by the following morphological characters: -a sculptured prodissoconch in Cyclochlamydidae n. fam. (uniformly smooth in Propeamussiidae); -a sometimes antimarginally sculptured right valve in Cyclochlamydidae n. fam. (smooth or weak commarginally sculptured in Propeamussiidae); -a simple outer prismatic layer of longitudinally hexagonal microstructure on the right valve in Cyclochlamydidae n. fam. (an outer layer of columnar calcite in Propeamussiidae).
Size: species of Cyclochlamydidae n. fam. measure 1.2 to 6 mm, whereas Propeamussiidae measure typically 5 to 120 mm in height.
Results of phylogenetic research attesting the monophyly of Cyclochlamydidae n. fam. will be published elsewhere.

Genus Cyclochlamys Finlay, 1926
Cyclochlamys aperta n. sp. ( -a rounded prodissoconch angle (obtuse in Cyclochlamys); -a lattice-sculptured prodissoconch on both valves (left valve antimarginal, right valve almost smooth in Cyclochlamys); -a simple outer layer of longitudinally hexagonal microstructure in preradial stage on the right valve (throughout right valve in Cyclochlamys); -and an antimarginal sculpture on the right valve (lacking in Cyclochlamys). Micropecten n. gen. also differs from Chlamydella by: -having a circular shape (more posteriorly oblique in Chlamydella), an antimarginal sculpture on both valves (smooth or commarginally sculptured on the left valve in Chlamydella); -a latticed sculptured conical left valve prodissoconch (weakly inflated and radially sculptured in Chlamydella); -a simple outer layer of longitudinally hexagonal microstructure in preradial stage on the right valve (throughout right valve in Chlamydella); -an antimarginal sculpture on the right valve (lacking in Cyclochlamys).