Cryptopora norfolkensis, 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 : 18-21

Cryptopora norfolkensis sp. nov.

( Fig. 4A –L)

Material examined. Norfolk 1 cruise: Éponge seamount, Norfolk Ridge, Stn DW 1692, 163 complete specimens plus 1 ventral valve, 2 dorsal valves; Introuvable seamount, Stn DW 1697, 119 complete specimens plus 1 ventral valve; Jumeau East seamount, Stn DW 1704, 5 complete specimens; Crypthelia seamount, Stn DW 1724, 2 complete specimens. Norfolk 2 cruise: Porthos seamount, Stn DW 2068, one complete specimen.

Holotype. The specimen illustrated in Fig. 4 D–F ( MNHN BRA- 3130).

Paratypes. The specimens illustrated in Fig. 4A–C , G–L ( MNHN BRA- 3131–35).

Type locality. Introuvable seamount, Norfolk Ridge, 24º39’ S, 168º38’ E, 569– 616 m.

Etymology. Alludes to the Norfolk Ridge.

Diagnosis. Small Cryptopora with rectimarginate anterior commissure. Beak high; beak ridges tuberculate. Foramen large, hypothyrid; deltidial plates narrow. Pedicle collar narrow, sessile. Teeth small, hooked, supported by parallel dental plates. Crura maniculiform with small, non-digitate distal extremities. Median septum triangular in profile.

Depth range. 400– 980 m.

Measurements (in mm).

Description. Shell very small, maximum observed length 2.5 mm, thin, weakly biconvex, oval to subpentagonal in outline. Lateral commissures straight, anterior commissure rectimarginate. Shell surface with very faint radial lines, more visible on the ventral valve; growth lines indistinct, numerous. Beak high, erect to slightly curved; beak ridges tuberculate. Foramen large, subtriangular, hypothyrid, posteriorly labiate, bounded by two narrow, disjunct deltidial plates. Ventral valve with a short, sessile pedicle collar. Teeth small, hooked, directed medianly, supported by parallel dental plates ( Fig. 4 J–L). Dorsal valve with narrow but high inner socket ridges, extending beyond the hinge margin. Cardinal process in form of a small, roughened depression. Crura incipiently divergent with small, non-serrated flattened endings ( Fig. 4 G–I). Median septum short but high, triangular in profile, not reaching the apex.

Remarks. This species differs from previously described Cryptopora species in its much smaller size. The deltidial plates bear the closest resemblance to those of C. gnomon (Jeffreys) , C. boettgeri Helmcke and C. maldivensis Muir-Wood ( Helmcke 1940; Cooper 1959; Muir-Wood 1959; Bitner 2008). Externally, the specimens from the Norfolk Ridge differ from C. gnomon in being rectimarginate and having tuberculate beak ridges while C. gnomon is sulcate and has smooth beak ridges ( Cooper 1959). Internally, the differences are also noticeable; in C. gnomon the flattened distal extremities are much larger and digitate. In addition, the profile of the median septum is very different in the two species ― in C. norfolkensis the septum is triangular in profile, not reaching the apex ( Fig. 4 H–I); in C. gnomon the septum is rectangular to axe-shaped, sloping steeply to the valve floor posteriorly and continuing in form of a low ridge to the apex ( Cooper 1959, pls 5C, 21D). The studied specimens also differ from C. maldivensis , which has divergent dental plates, crura with much larger distal extremities, and an axe-shaped septum that, as in C. gnomon , continues as a low ridge to the apex ( Muir-Wood 1959; Bitner 2008, fig. 3K, L). Also C. boettgeri has an axe-like septum and its crura have large flattened endings with distinct serrations ( Helmcke 1940) ― characters not observed in the studied material. Additionally the pedicle collar in C. boettgeri is wide and excavated, unlike that in C. norfolkensis .

Figures

FIGURE 4. A – C, Cryptopora norfolkensis sp. nov., Norfolk Ridge, Norfolk 1. A, dorsal view of young complete specimen, paratype, MNHN BRA- 3131, Stn DW 1692, 507 – 967 m; B, C, dorsal view of complete specimen and enlargement of the umbonal part to show details of the beak, paratype, MNHN BRA- 3132, Stn DW 1697, 237 – 250 m; D – F, dorsal view of complete specimen, and enlargement of the umbonal part to show details of the beak (E) and fine capillation anterior to the protegular node (F), holotype, MNHN BRA- 3130, DW 1697, 237 – 250 m; G – I, dorsal valves, paratypes, Stn DW 1692, 507 – 967 m, G, H, inner and oblique views to show septum and crura, MNHN BRA- 3133, I, enlargement of posterior part to show details of cardinalia and crura, MNHN BRA- 3134; J – K, ventral valve, paratype, MNHN BRA- 3135, Stn DW 1692, 507 – 967 m, inner view, and enlargement of tilted views to show dental plates. All SEM.