Etymology: Not defined by Hedley (1905). Specific epithet from ‘furca’ (Latin noun for fork) and suffix ‘-fera’ (Latin for bearing/carrying; feminine singular of suffix -fer), likely describing either the strong anterior folding or perhaps the distinctive brachidium.

Description

Overall valve form: Maximum valve length 33.7 mm (average 28.5 mm, SD 2.9, smallest 22.2 mm long). Valves relatively narrow, W%L averaging 62.6% (SD 4.7, range 56.2%−73.2%), and relatively thick, T%L averaging 60.6% (SD 3.6, range 52.8%−70.0%).

Overall outline (viewed dorso-ventrally) elongate sub-rectangular or sub-pentagonal, widest point approximately midway along length with anterior margin truncated. Valves biconvex from lateral profile, ventral (pedicle) valve deeper. Lateral commissure dorsally convex, gently curved towards dorsal (brachial) valve (see dorsal and lateral aspects Fig. 3 A–C). Anterior commissure weakly to strongly intraplicate (plicosulcate)[1], dorsal valve with small antero-medial ridge folding dorsally, flanked by shallow grooves folding ventrally and creating a shallow antero-medial groove on the ventral valve (Fig. 3 D). On some smaller specimens, as well as the largest and most thickened specimens, the anterior commissure folding was irregular (see Fig. 3 E, F). Holotype specimen similar but elongate sub-triangular in overall outline, with the widest point closer to the anterior end of the valves (Fig. 4 A–F).

Valves punctate, increasingly thick and rough on larger specimens, the growth striae becoming low ridges. Radial ribs/costae absent. Colouration cream or yellowish-brown.

Dorsal (brachial) valve: Cardinal margin angle obtuse (~100−106°). Cardinal process small, produced as a rectangular plate folded anteriorly from the umbo, with a deep indentation anterior to the process and an oval myophore on the posterior face. Hinge sockets well defined but ridges are relatively small, socket ridges diverging at approximately 71–86° (to antero-posterior axis), relatively flat (only gently inclined ventrally). Outer hinge plates small and slightly grooved, demarcated from inner plates by fairly poorly-developed crural bases (bases narrow, outer edges somewhat continuous with inner socket ridges). Inner hinge plates fused medially as a lightly excavate septalium (excavation running posteriorly to the cardinal process), supported by the median septum. Septalium anterior border V-shaped and either just reaching level of crural processes or extending anteriorly slightly beyond them (cardinal process, socket ridges and hinge plates illustrated in Fig. 3 G, H; specimen with longer septalium in Fig. 3 I). Brachidium illustrated from two specimens, one with narrower brachidium (Fig. 3 I–K) and one wider and longer (Fig. 3 L–N). Crura short, weakly diverging (from antero-posterior axis) or subparallel (on Holotype). Crural processes moderately long and pointed, directed ventrally (and slightly medially) (see Fig. 3 J, N, Fig. 4 G, H). Brachidium diploform (‘campagiform’), descending branches broad and ribbon like, fused posteriorly with the crural process, and with short and thin lateral bands connecting with the median septum. Ascending branches and transverse band very high, forming a large hood/funnel, anterior-most extent of loop ~66%−75% dorsal valve length (see different aspects in Fig. 3 I–N, Fig. 4 D, G, H). Transverse band with pair of antero-lateral folds, demarcating a medial indentation of reduced height (see Fig. 3 K). Median septum thin, initially dropping in height anterior to hinge plates before rising to the highest point where the lateral bands connect, rapidly dropping off anterior to this but not extending beyond brachial loop, terminating approximately 40%−65% dorsal valve length).

Ventral (pedicle) valve: Beak moderately small (length ~14%−17% overall length), suberect. Foramen subapical to transapical (posteriorly against border, ‘marginate’ per Thomson 1927), moderately large (diameter approximately 8%−10% overall valve length), permesothyridid, beak ridges poorly defined. Pedicle collar very short (little more than a ring in the foramen opening). Deltidial plates mostly exposed, fused (i.e., as a symphytium) with little trace of a medial seam on material examined. Hinge teeth relatively small, bases not thickened (however, tooth−socket connection was very strong, and on the two specimens examined to illustrate brachidia, the hinge could not be disarticulated). Dental plates absent. Deltidial plates and hinge teeth illustrated in Fig. 3 A, G, H, Fig. 4 C, and others).

Soft tissue: Pedicle short (not extending beyond the beak), its end rough/papillate (Supplementary Fig. 1 A). Lophophore plectolophous (Supplementary Fig. 1 B). Gonad development apparent in some specimens, gonads narrow and confined to posterior half of valves (see Fig. 3 A).

Attachment substrata and epibiota: Approximately 36% of examined specimens were attached. Substrata varied but were small to large (size ≤ valve length) and included serpulid tubes, empty whole shells or worn fragments (including those of the brachiopod Basiliolella colurnus), and bryozoan colony fragments. Epibiota was mostly small encrusting sponges or brown films of microorganisms, the Holotype specimen had encrusted tubes on the ventral valve, possibly from Serpulid worms.

[1]Intraplicate (or plicosulcate) describes alternate folding, with dorsal ridge having a small median fold (relative to the stronger ventral folds flanking it), this is similar to parasulcate where the median fold is much stronger (and ventral folds weaker).