Ospreyella depressa, LÜTER & WÖRHEIDE & REITNER, 2003

LÜTER, CARSTEN, WÖRHEIDE, GERT & REITNER, JOACHIM, 2003, A new thecideid genus and species (Brachiopoda, Recent) from submarine caves of Osprey Reef (Queensland Plateau, Coral Sea, Australia), Journal of Natural History 37 (12), pp. 1423-1432 : 1425-1429

Ospreyella depressa sp. n.

( figures 2, 3 )

HOLOTYPE. One mature female with one pair of median tentacles and an empty brood pouch, collected at station 2, 14 December 1999, fixed in glutaraldehyde, preserved in alcohol, dorsal and ventral valve separated ( figure 2A, B). Accession number: QM G318534 , Queensland Museum , Brisbane, Australia.

PARATYPES. Six females, 11 males, two adults (sex unknown), one juvenile. All collected 14 December 1999. For details see table 1.

Etymology. Species name derived from Latin ‘ deprimere ’, meaning ‘to press down’ or ‘to sink’ in accordance with the deep median depression in the dorsal valve.

Diagnosis. Same as for the genus. Dorsal valve with median depression. Median ramus concave, basally connected to the dorsal part of the interbrachial ridge, whilst ascending it bends back towards the posterior bridge, forming small jugum at its end ( figure 2J). Ramuli very short, slightly reticulated, directly attached to left and right parts of median ramus, together with basal part of median ramus the short ramuli build the basis of the central part of lophophore-supporting apparatus ( figure 2D). Two major interbrachial lobes with strongly serrated and denticulated edges ( figure 3 ). Two minor interbrachial lobes with branches ( figures 2C, 3 ). Branches surrounded by thin calcified walls; walls without connection to the median part of the dorsal valve’s floor, wall’s edges with irregular tubercles and protuberances ( figure 3B ) becoming more conspicious with maturity of the animal.

Description. Shell calcified, medium-sized (size measurements in table 2), biconvex, clearly uniplicate, endopunctate, slightly ‘heart-shaped’ in dorsal view, with straight hinge line; ventral valve larger, cup-shaped, posterior part (umbonal area) of ventral valve attached to substratum, with flat interarea and raised, triangular pseudodeltidium, interarea and pseudodeltidium short (ca. one-quarter to onethird of total shell length), slightly curved, variable in orientation; dorsal valve lid-like, oval with straight posterior margin, wider than long, smaller than ventral valve, with irregular growth lines.

Floor of ventral valve irregular, slightly papillose, with prominent papillae near edge, posteriorly with two oval gonad pits on either side; large teeth, bilobed hemispondylium with prominent upraised median myophragm ( figure 2G), lobes and myophragm connected by calcified horizontal septum, horizontal septum sometimes with frontal sinus-like indentation on either side of the myophragm; lobes of hemispondylium slightly raised and pointed; ventral valve without median septum.

Dorsal valve with dental sockets, and slightly trilobed cardinal process with bulbous central ridge ( figure 2C, J). Outer rim of dorsal valve strongly papillose with papillae fading out towards median depression ( figure 2C, D); prominent posterior bridge with (female) or without (male) marsupial notch (sexual dimorphism) ( figure 2 H–J). Two outer large interbrachial lobes and two inner minor interbrachial lobes, the latter with up to four furcations, orientation of furcating branches always towards median anterior / posterior axis. Number of branches increasing with maturity. Thin calcified walls surrounding interbrachial lobes with irregularly shaped, calcified protuberances and tubercles and serrated edges. Median ramus ascending from dorsal, posterior wall of interbrachial ridge as concave channel, forming small jugum at its end, where it is connected to minor interbrachial lobes; minor interbrachial lobes slightly reticulated where connected to jugum ( figure 2).

Mantle spiculate, with plate-like spicules covering and protecting gonads in ventral valve. Shallow coelomic cavity in ventral valve, without obvious mantle canals. Mantle ascending towards hinge line, thereby enlarging the body cavity in the umbonal area. Mature females with single median brood pouch, bulb-shaped brood pouch built by invagination of the ventral mantle, brood pouch with one small central opening into mantle cavity. Dark red-coloured coelomocytes distributed in the coelom, more obvious in ventral valve, but also abundant in lophophore coelom. Lophophore ptycholophe, following all furcations of the minor interbrachial lobes, with dense row of contractile tentacles. Mature females with two specialized median tentacles (sexual dimorphism) ( figure 2A), supported by marsupial notch (see above) ( figure 2H, I). Orientation of specialized tentacles towards brood pouch in mantle of ventral valve, with distal ends extending into pouch. Specialized tentacles slightly thicker than ordinary lophophore tentacles, with pear-shaped gladular tips (sticky when touched during preparation). If present, larvae densely packed in the brood pouch, surrounding distal ends of specialized median tentacles. Adult males without marsupial notch, specialized pair of tentacles or brood pouch ( figure 2J).

In early juveniles median ramus, large interbrachial lobes and bridge already present, with minor interbrachial lobes developing later ( figure 2E, F).

Figures

FIG. 3. Ospreyella depressa sp. n., camera lucida drawings. (A) Dorsal valve of female paratype (QM G318541) showing diagnostic characters, i.e. median depression (dep), furcating minor interbrachial lobes (mil), the trilobed cardinal process (cp) and marsupial notch (mn). (B) Male paratype (ZMB 2004), notice the steep median ramus (mr) and the median jugum (ju), cardinal process slightly damaged during preparation. Scale bars: 1 mm.