Ebiscothyris bellonensis Bitner & Cohen 2015
Creators: name: Bitner, Maria Aleksandra
name: Cohen, Bernard L.
Publisher: name: Zenodo
Year: 2015
Subjects: Biodiversity
Taxonomy
Animalia
Brachiopoda
Rhynchonellata
Terebratulida
Terebratulidae
Ebiscothyris
Ebiscothyris bellonensis

description: EBISCOTHYRIS BELLONENSIS GEN. ET SP. NOV.
(FIGS 7A–I, 8A–F, 9A–D)
Diagnosis
As for the genus.
Etymology
Referring to the Bellona Plateau, where part of the material was collected.
Holotype
The specimen illustrated in Figure 7E–H, IB-2013-1, was collected at station CP 2616 on the Chesterfield Plateau.
Paratypes
The specimens illustrated in Figures 7A–D, I and 8A– F, IB-2013-2 to IB-2013-6, were collected at stations CP 2557 and CP 2616.
Type locality
Cruise EBISCO, station CP 2616, Coral Sea, Chesterfield Plateau, 19°35.08′S, 158°49.83′E, 786–836 m depth.
Material examined
Coral Sea, cruise EBISCO, western Bellona Plateau: station DW 2544, 21°09.91′S, 158°38.15′E, 650– 723 m depth, five specimens; station CP 2545, 21°10.04′S, 158°37.40′E, 765–778 m depth, three specimens; station CP 2556, 21°05.29′S, 158°33.72′E, 741– 791 m depth, nine specimens; station CP 2557, 21°06.05′S, 158°31.66′E, 800–923 m depth, three specimens. Chesterfield Plateau: station CP 2616, 19°35.08′S, 158°49.83′E, 786–836 m depth, 28 specimens.
Depth range
650–923 m.
Measurements (station, length, width, and thickness, all in mm)
CP 2616 (holotype), 13.1, 12.0, 8.1; CP 2616 (paratype), 13.1, 12.3, 7.1. Measurements of all currently available specimens of E. bellonensis gen. et sp. nov. are given in Appendix S7.
Description
Shell of medium size, white, thin to translucent anteriorly, elongate oval to subpentagonal in outline, with maximum width at about mid valve. Shell surface smooth, with weakly defined growth lines; lateral and anterior valve margins slightly incurved, thickened (Fig. 7C, D, G, H). Shell biconvex, ventral valve more convex. Lateral commissures dorsally curved, anteri- or commissure strongly and broadly unisulcate. Beak short, suberect to erect. Foramen of medium size, circular, permesothyrid. Deltidial plates conjunct, forming a well-exposed symphytium with only a weak median line of junction in some specimens (cf. Fig. 8A). Pedicle variable, may be as much as ten times as long as the shell (Fig. 7I). The long pedicle differentiates E. bellonensis gen. et sp. nov. from Abyssothyris and other terebratulids. Ventral valve interior with welldeveloped tubular, excavate pedicle collar (Fig. 8F). Teeth small, short (Fig. 8A). Dorsal valve interior with long and medially inclined inner socket ridges that bound wide sockets; fulcral plates well developed. Cardinal process prominent, semi-elliptical (Fig. 8D, F). Outer hinge plates narrow, triangular; crural bases ill defined. Loop short, occupying about 25% of dorsal valve length, with blunt, short, crural processes directed ventrally (Fig. 8B–E). Descending branches subparallel, very wide; transverse band broad, medially folded. Muscle scars strongly impressed on both valves, elongate oval in outline.
Ultrastructural analysis shows three shell layers (Fig. 9A–D). The microgranular primary layer is 5.2– 7.8 μm thick, the secondary layer is very thin (3.2– 5.6 μm), and its fibres are wide, implying that mantle epithelial cells are large, and/or that the angle between the fibres and the primary layer is small. In transverse section, the secondary layer shows only two overlapping layers of fibres (Fig. 9B), a feature that has only been reported before in the dyscoliid Xenobrochus norfolkensis Bitner, 2011 (Bitner, 2011: fig. 4E, F); however, the incurved, thickened valve margins are built of several, densely arranged sheets of secondary fibres (see Fig. 9C). The tertiary layer of E. bellonensis gen. et sp. nov. is thick (85–152 μm), with its internal surface showing clear traces of large, irregularly interlocking prisms (Fig. 9C, D). The total shell thickness is 96–160 μm. In Kanakythyris (Fig. 9E, F) the shell is also composed of three layers; however, the secondary layer is much thicker, and the prisms are more irregular on the internal surface, and display delicate ornamentation (Fig. 9F), whereas in E. bellonensis gen. et sp. nov. they are smooth (see Fig. 9D).
description: Published as part of Bitner, Maria Aleksandra & Cohen, Bernard L., 2015, Congruence and conflict: case studies of morphotaxonomy versus rDNA gene tree phylogeny among articulate brachiopods (Brachiopoda: Rhynchonelliformea), with description of a new genus, pp. 486-504 in Zoological Journal of the Linnean Society 173 (2) on pages 494-495, DOI: 10.1111/zoj.12217, http://zenodo.org/record/5454597