Pulvinites exempla, (HEDLEY, 1914)

Tëmkin, Ilya, 2006, Anatomy, shell morphology, and microstructure of the living fossil Pulvinites exempla (Hedley, 1914) (Mollusca: Bivalvia: Pulvinitidae), Zoological Journal of the Linnean Society 148 (3), pp. 523-552 : 525-526

PULVINITES EXEMPLA ( HEDLEY, 1914) (PERFORATED

OYSTER; MACPHERSON & GABRIEL, 1962)

Synonymy

Foramelina exempla Hedley, 1914: 71–72 , plate 11, figure 6, plate 12, figures 7, 8 (original description); – Hedley, 1918: M7 (faunal list); – Thiele, 1934: 802 (brief description); – Macpherson & Chapple, 1951: 144 (faunal list); Iredale & McMichael, 1962: 10 (faunal list); – Macpherson & Gabriel, 1962: 294–295, figure 336 (description); – Cox, 1969: N326–327, figures C53, 3a, b (diagnosis of Foramelina ); – Fischer-Piette, 1976: 40 (synonymy); – Tenner, 1981: 3.

Pulvinites exempla ( Hedley, 1914) . – Palmer, 1984: 823, plate 72, figure 6 (revision); – Butler, 1998: 265, figure 6.11 (description); – Lamprell & Healy, 1998: 110–111, figure 267 (brief description); – Marshall, 1998: 99–102, figures 1–9 (hinge and prodissoconch figured; ecology); – Malchus, 2004a: 1547 (prodissoconch and ligament); – Malchus, 2004b: 96 (prodissoconch); – Tëmkin, 2006 (phylogeny).

Pulvinites (Pulvinites) exempla ( Hedley, 1914) . – Pacaud, 2001: 6, 9, 12–14, figure 4(A) (comparison with extinct Pulvinites spp. ).

Note: The review of the Recent Pulvinitidae by Boss (1982: 1115) undoubtedly refers to Pulvinites exempla , but is not included in the synonymy because it does not contain the species name. Likewise, Franc (1960: 2081) did not explicitly name the species in his treatment of Foramelina that he placed in the family Isognomonidae Woodring, 1925 .

Material examined

Lectotype (see below): AMS C.170923 (one pair + byssus), 38°8′S, 149°55′E, Australia, VIC, south of Gabo Island, 183–457 m [‘type’ on hand-written label and ‘holotype’ on printed label; ‘holotype’ in Palmer (1984) and Marshall (1998); figured in Hedley (1914: plate 11, figure 6)].

Paralectotype (see below): AMS C.037004 ( RV), 38°8′S, 149°55′E, Australia, VIC, south of Gabo Island, 183–457 m [‘cotype’ on hand-written label and ‘paratype’ on printed label; ‘paratype’ in Palmer (1984) and Marshall (1998); figured in Hedley (1914: plate 12, figures 7, 8), Macpherson & Gabriel (1962: 295, figure 336); Cox (1969: N327, figures C53, 3a, b), Palmer (1984: plate 72, figure 6), Butler (1998: 265, figure 6.11), Pacaud (2001: 12, figure 4A)].

Other material: AMS C.122000 (one pair), 33°51′S, 151°41′E, Australia, New South Wales, east of Sydney , 400 m, trawled ; AMS C.126893 (one pair; RV fragment), 33°50.000′S, 151°43.500′E, Australia, New South Wales, off Sydney , 457 m, trawled ; AMS C.129659 (four pairs with tissue + one juvenile pair fragment), 33°42.000′S, 151°53.000′− 152°0.000′E, Australia, New South Wales, north-north-east of Sydney , 406 m, on a junked aeroplane, trawled ; NMNZ M.153627 (one pair), 45°18.93′S, 166°68.36′E, New Zealand, South Island, off point east of Joseph Point, Doubrful Sound , Fioedland , 340 m ; NMNZ M.150090 (one individual tissue only +>100 D- stage larvae), 37°41.3′S, 179°00.7′E, off East Cape , 936 m.

Lectotype and paralectotype designation: The original description by Hedley (1914), essentially based on a single specimen ( AMS C.170923), mentions that the same lot contained a second specimen ( AMS C.037004). Both specimens are illustrated in the original work, although no types were designated. According to ICZN (1999: Art. 72.1.1), both specimens constitute a type series and qualify as syntypes because the explicit designation of either of the specimens as a holotype is lacking. Subsequent designation of AMS C.170923 [= C37003 of Palmer (1984)] as the ‘holotype’ and AMS C.037004 [= C37004 of Palmer (1984)] as a ‘paratype’ by Palmer (1984) is not valid according to ICZN (1999) rulings for the following reasons. ICZN (1999: Art. 74.6) (Fixation of lectotype by inference of ‘holotype’ or ‘the type’ before 2000) does not apply because it requires that the original description is based on a single specimen. This condition is clearly not satisfied because the presence of more than one specimen in the type series is unequivocally acknowledged by both authors: Hedley (1914), who mentioned and illustrated both specimens, and Palmer (1984), who established both holotype and paratype based on this description. ICZN (1999: Art. 74.5) permits the use of the term ‘holotype’ in a lectotype designation made before 2000 if the author had unambiguously selected a particular syntype and explicitly indicated that it was selected from the type series to serve as the name-bearing type. Despite the fact that Palmer’s designation does not explicitly refer to the specific specimens from Hedley’s type series, the correspondence between the two was verified in the present revision by examination of original labels that accompany the specimens from the type series. Consequently, the designation of lectotype and paralectotype by Palmer (1984) is valid according to ICZN (1999: Art. 74.5) despite the wrong use of the term ‘holotype’.

Original diagnosis and description: ‘Shell equivalve, equilateral, large, flat, discoidal, margin irregular in outline. Valves thick, composed of brittle, imbricating lamellae which both include and are overlaid by a thin membranous epidermis, where eroded of a silvery sheen, interior a dark bronze. Perforation in the right valve about 10 mm in diameter, median and subumbonal, internally with a raised margin, externally excavated as an oblique furrow ascending to the vertex. From the margin of the perforation a suture leads to the anterior extremity of the hinge plate. Byssus a dense bundle of threads about half an inch long. Hinge line about 43 mm long. Area much eroded above and traversed by about 22 narrow ligamental grooves which slightly radiate from above. Externally the hinge gapes when the valves are closed as in Melina [= Isognomon Solander in Lightfoot, 1786]. Adductor small, subcircular, about its own breadth below the perforation. Byssal retractor rather larger than the adductor and immediately above it in the left valve. Pallial margin entire, about half an inch within the ventral margin. Height, 120; length, 130 mm’ ( Hedley, 1914: 71).

Emended diagnosis by Palmer (1984: 823): ‘Distinguished from other species of Pulvinites by its large size when adult, and by features related to size, such as the greater number of ligament pits and their greater size and spacing.

Emended diagnosis: Pterioidean with nongyrate and subcircular in shape prodissoconch; anterior part of visceral mass greatly contorted to right side; pairs of left and right anterior pedobyssal retractor muscles fused at tips; outermost mantle fold (OF-2) displaced proximally forming pallial skirt; larvae present in gills of brooding adults.