Annuloplatidia richeri, Bitner, Maria Aleksandra, 2009

Bitner, Maria Aleksandra, 2009, Recent Brachiopoda from the Norfolk Ridge, New Caledonia, with description of four new species, Zootaxa 2235, pp. 1-39 : 25-26

Annuloplatidia richeri sp. nov.

( Fig. 10 A–K)

Material examined. Norfolk 1 cruise, Éponge seamount, Stn DW 1692, 178 complete specimens, one ventral valve; Jumeau East seamount, Stn DW 1704, 3 complete specimens; Crypthelia seamount, Stn DW 1724, 9 complete, 3 ventral valves, one dorsal valve.

Holotype. The specimen in Figure 10 J–L ( MNHN BRA- 3161).

Paratypes. The specimens in Fig. 10 A–I ( MNHN BRA- 3162–3166).

Type locality. Jumeau East seamount, Norfolk Ridge, Stn DW 1704, 23 °45’ S, 168°16’ E, 400– 420 m.

Etymology. In honour of Dr Bertrand Richer de Forges, IRD, Nouméa, cruise leader on Norfolk 1 and 2.

Diagnosis. Annuloplatidia with ventral valve densely pustulose. Dental plates and short ventral median ridge present. Crura long, descending branches attached directly to the short ascending branches connected by a transverse band. Dorsal septum very high, triangular in profile.

Depth range. 200– 967 m.

Measurements. (in mm).

Station Length Width Thickness Number Depth (m)

DW 1692 507–967 1.1–2.1 1.0–2.1 0.3–0.8 DW 1704 400–420 1.0–1.8 0.9–2.0 0.3–0.7

Description. Shell very small with maximum length 2.1 mm, conspicuously punctate. Shell outline very variable, from elongate oval, subcircular to transversely oval or widely subtriangular, usually wider than long in adults; sometimes shell outline irregular if dorsal valve closely applied to the substratum because of a very short pedicle. Ventral valve gently convex, dorsal valve flat anteriorly, slightly convex posteriorly. Ventral valve surface covered with numerous prominent, transversely elongate pustules, dorsal valve surface smooth with very faint radial lines; growth lines numerous on both valves. Beak very short with distinct ridges. Foramen large, subcircular, amphithyrid, flanked by very narrow deltidial plates. Ventral valve interior with sessile, relatively wide pedicle collar and short median ridge in umbonal region, not reaching apex, however ( Fig. 10 B, C). Teeth small, hooked with short dental plates. Dorsal valve interior with prominent inner socket ridges. Crura long, crural processes indistinct. Descending branches directly attached to short ascending branches, these connected by transverse band ( Fig. 10 D–G). Dorsal median septum very high, triangular in profile.

Remarks. The genus Annuloplatidia was erected for those platidiid brachiopods that have ascending branches connected by a transverse band ( Zezina 1981b). So far three species of this genus have been described, i.e. A. annulata ( Atkins, 1959) known from the Atlantic and Eastern Pacific, A. horni (Gabb, 1861) from the Pacific coast of North America, and A. indopacifica Zezina, 1981 b from the Western Pacific and eastern part of the Indian Ocean. Annuloplatidia richeri sp. nov. can be readily distinguished from these species in that the ventral valve is densely covered with pustules; in the other species the ventral valve surface is smooth ( Atkins 1959; Bernard 1972; Zezina 1981b; Lüter 2007), although in some specimens of A. annulata the surface can be slightly wrinkled or pustulose ( Lüter 2007). Annuloplatidia richeri is half as big as A. annulata ( Atkins 1959; Lüter 2007). Being equal to the maximum length of A. richeri , A. annulata lacks fully developed descending branches ( Atkins 1959: fig. 4). The latter species also has a narrower pedicle collar, and its ventral median septum runs anteriorly from the pedicle collar ( Atkins 1959). Annuloplatidia horni has a ventral valve ornamented by radial lines and lacks, or has very weakly developed, dental plates (Hartlein & Grant 1944; Bernard 1972).

Annuloplatidia richeri is also readily distinguished by its smaller size, presence of a ventral septum and hooked teeth, from Western Pacific A. indopacifica , which has teeth in the form of elongate ridges ( Zezina 1981b).

Figures

FIGURE 10. Annuloplatidia richeri sp. nov., Norfolk Ridge, Norfolk 1: A, dorsal view of complete young specimen, paratype, MNHN BRA- 3162, Stn DW 1704, 400 – 420 m; B, C, inner view of ventral valve and enlargement of the posterior part (C), paratype, MNHN BRA- 3163, Stn DW 1692, 507 – 967 m; D – G, dorsal valve, inner, lateral and anterior views, and enlargement (G) to show details of brachidium, paratype, MNHN BRA- 3164, Stn DW 1692, 507 – 967 m; H, I, dorsal views of complete specimens, paratypes, MNHN BRA- 3165 – 3166, Stn DW 1704, 400 – 420 m; J – L, ventral and dorsal views of complete specimen, and enlargement of the ventral shell surface to show nodes, holotype, MNHN BRA- 3161, Stn DW 1704, 400 – 420 m. All SEM.