Aequipecten wagenaari Marquet & Dijkstra, 2000
MARQUET, R. & H. H. DIJKSTRA. 2000. Pliocene species of Aequipecten (Mollusca, Bivalvia, Pectinidae) from the North Sea Basin. Contributions to Tertiary and Quaternary Geology, 37 (3.4): 39-55. [p. 45, pl. 2, fig. 2]
2000 Aequipecten wagenaari Marquet & Dijkstra, 2000
R. Marquet & H. H. Dijkstra, 2000, plate 2.
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«Derivatio nominis — In honour of Mr M. Wagenaar, for his valuable help in producing the photographs which illustrate this and previous papers.
Locus typicus — Kallo (Verrebroekdok), province of Oost-Vlaanderen, Belgium. Stratum typicum — Lillo Formation Oorderen Member (Cultellus level), Middle Pliocene. Types - Holotype is IRScNB IST 6401, paratypes are IRScNB IST 6402 and RGM 456 050. Material studied — In addition to the type specimens, we have studied the following specimens (all in RM Colln): Kallo (Verrebroekdok, Oorderen Member, Angulus benedeni level, 2 v); Kallo (Verrebroekdok Oorderen Member, Atrina level, 1 v); Kallo (Verrebroekdok Oorderen Member, basal level, 14 v); Kallo (Verrebroekdok, Oorderen Member, Cultellus level, 66 v); Antwerp (E\mg Borgerhout, mixed derived Pliocene, 3 v); Orford (The Broom, Suffolk, Coralline Crag, 2 v); Sutton (Sudbourne Park Pit, SufTollc, Coralline Crag, 1 v); Walton-on-the-Naze (The Naze, Essex, Waltonian Red Crag, 2 v). Of A. malvinae (du Bois de Montpereux, 1831), we have studied one valve from Lychow (Tarnobrzeg, Poland) of Middle Miocene age (RM Colln). Of A. elegans (Andrzejowski, 1820). we have studied material from Weglin (Trzydniczanca valley, Tanobrzeg, Poland, Middle Miocene, 19 v, RM Colln), of A. vasconiensis (Cossmann & Peyrot, 1914), specimens from Mios (Ruisseau de Surgenne, Gironde, Falun de Mios, 'Sallomacian', 6 v, RM Colln), of A. degrangei (Cossmann & Peyrot, 1914), eight valves from Salles (Ruisseau de Minoy, Gironde, Falun de Salles, Middle Miocene, RM Colln), of A. raouli (Cossmann & Peyrot, 1914), two valves from the same locality and level (RM Colln), and of A. seniensis (Lamarck, 1819) material from Antwerp (Ploegstraat 29, Berchem Formation, Antwerp Member, Panopea level, 21 v, RM Colln); Antwerp (Schijnpoort, same level, 25 v, RM Colln); Baldichieri (orchard on road to Monale, Asti, Italy, Wddle Pliocene, 23 v, RM Colln), and Diolo (calanca on road to Chiavenna, province of Piacenza, Italy, Piacenzian, Middle Pliocene. 37 v and 1 bv, RM Colln). Dimensions — Height (holotype) 18.6 mm, length 18.4 mm, diameter 4.6 mm; paratype IRScNB IST 6402 (left valve), height 19.3 mm, length 19.5 mm, diameter: 4.0 mm; paratype RGM 456 050 (right valve), height 20.7 mm, length 20.0 mm, diameter 5.6 mm. For height and length of a sample of 50 specimens see Fig. 5. Diagnosis — Rather small (c. 30 mm in height) species with near-circular, strongly tumid disc, with a primary radial rib number of 15, without secondary radial ornament, with rather heavy commarginal ornament, forming scales on junctions with radial ornament, and with auricles which together measure about 314 to 213 of total shell length. Description — Rather small species, with a maximum height of 32.0 mm (see Fig. 5); shell solid, slightly inequilateral and inequivalve. Disc nearly orbicular, but height mostly exceeding length. Shell rather tumid, left valve flatter than right. Ornament at first consisting of 15 primary radial ribs (see Fig. 6), which in the majority of specimens are not divided into secondaq ribs; this occurs only exceptionally in the largest specimens. Width of radial ribs about a thlrd of the intercostal spaces on left valve, to a third on the right valve, which is usually more strongly ornamented than the left one. Growth lines form low scales in intercostal spaces, on the ribs are high, hollow scales. Hinge line nearly always straight. Auricles comparatively large, to more than 314 of total length in juvenile specimens and 213 in adults. Anterior auricle twice as large as posterior, with a deep byssal notch. In the area between disc and auricles occurs antimarginal ornament, especially anteriorly. Anterior auricle with six radial ribs, posterior one with three. Anteriorly, clear scales are present on the radials. Auricular denticles anteriorly clearly visible, ctenolium well developed, with five teeth visible on the inside of the shell. Ligament pit broadly triangular, shallow. Hinge line with ridges, parallel to margin. Radial ribs clearly visible on the inside of the shell, muscle insertion vague.» ROBERT MARQUET & HENK H. DIJKSTRA, 2000
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