Amphithyris comitodentis, Nauendorf, Alice, Wörheide, Gert & Lüter, Carsten, 2014

Nauendorf, Alice, Wörheide, Gert & Lüter, Carsten, 2014, Revision of the brachiopod genus Amphithyris (Rhynchonelliformea: Platidiidae) with descriptions of two new species, Zootaxa 3847 (2), pp. 221-240 : 232

Amphithyris comitodentis n. sp.

( Fig. 6 ; Table 5 )

as Amphithyris buckmani Lüter 2008 : p. 316, fig. 2F–G (misidentification)

Type material. Holotype: NIWA 92391, Paratypes: ZMB Bra 2054, ZMB Bra 2145, ZMB Bra 2281, ZMB Bra 2353, ZMB Bra 2354 (20 specimens).

Etymology. From Latin comitans ("accompanying, parallel") and dens ("tooth") referring to the fact that this is the only species within Amphithyris with its teeth parallel to the hinge line.

Type locality. SW Pacific east of New Zealand; SO168; Stations 13, 96, 97, 99, 105. Depth range: 252–1865 m.

Diagnosis. Shell planoconvex, flat dorsal valve, prints of capillae on ventral valve interior. Hinge teeth flat, narrow, parallel to hinge line. Small dorsal septum.

Description. Shells planoconvex, oval to round. Dorsal valve almost flat ( Fig. 6 A) with low median septum, highest point mid-valve ( Fig. 6 A). Foramen amphithyrid with pair of short socket ridges at lateral margins that slightly reach over posterior margin ( Fig. 6 A). Ventral valve with imprints of capillae on interior ( Fig. 6 B and D). Hinge teeth narrow, parallel to hinge line ( Fig. 6 C and D), delthyrium triangular. Ventral valve with concentric growth lines on exterior ( Fig. 6 E). Protegulum on caudal tip of ventral valve with wrinkled surface ( Fig. 6 F).

Remarks. The specimens erroneously assigned to Amphithyris buckmani by Lüter (2008) show a consistent character difference to all other Amphithyris spp., i.e. the longitudinal axis of their hinge teeth is parallel to the hinge line. We therefore describe it as a new species Amphithyris comitodentis n. sp. It features similar characteristics to the other Amphithyris species such as small size, shell convexity, an asymmetrical dorsal valve due to irregular substrate morphology, an amphithyrid foramen and a triangular delthyrium. The specimens feature capillae imprints in the ventral valve interior as in A. hallettensis and a low dorsal septum as in A. buckmani , A. hallettensis and A. seminula .

Figures

FIGURE 6. Amphithyris comitodentis n. sp. A – C. Holotype NIWA 92391. A. Dorsal valve interior, showing low median septum. B. Ventral valve interior. C. Detail of B showing teeth in parallel orientation to hinge line highlighted by dashed lines. D. Paratype ZMB Bra 2054, v entral valve interior showing imprints of capillae and tooth orientation. E – F. Paratype ZMB Bra 2353. E. Ventral valve exterior with concentric growth lines. F. Close-up of ventral protegulum showing a wrinkled surface. Scale bars: A – E = 200 µm; F = 20 µm.