Pseudotrapezium groenlandicum Spath 1936

• Main Authors: Hryniewicz, Krzysztof, Little, Crispin T. S., Nakrem, Hans Arne
• Format: Other/Unknown Material
• Language: unknown
• Published: 2014
• Subjects: Biodiversity; Taxonomy; Animalia; Mollusca; Bivalvia; Venerida; Arcticidae; Pseudotrapezium; Pseudotrapezium groenlandicum; Greenland; Milne Land; Svalbard; East Greenland
• Online Access: https://zenodo.org/record/5228265; https://doi.org/10.5281/zenodo.5228265

Pseudotrapezium aff. groenlandicum Spath, 1936 (Figure 16 H–P) 1936 aff. Pseudotrapezium groenlandicum sp. nov. —Spath, p. 125, pl. 49, fig. 7a–c. ? 1982 aff. Hartwellia (Hartwellia) groenlandica (Spath) —Fürsich, p. 89. 2011 Arcticid—Hammer et al., fig. 7m, tab. 2. Material examined. 820 specimens, mostly articulated or semi-articulated shells and internal moulds. See Appendix 1 for list of specimens. Dimensions. 12–15 mm in length, 9.8–11 mm in height, 8–10 mm in width. See Figure 18 A–D and Appendix 2L for details. Description. Small, moderately inflated with very thin shell. Beaks prosogyrate, very strongly incurved. Lunule moderately deep. Anterior margin projecting, arcuate, passing into broadly arched ventral margin. Posterior area with two carinae, posteroventral extremity slightly rostrate where intersected by first carina, passing into truncated oblique posterior margin. Second carina weak, parallel to the posterodorsal margin. Posterodorsal margin straight. External ornament composed of very weak commarginal growth lines. Hinge plate large and thick; lateral tooth AI developed, separated from 1; 3a absent. 1 and 3b separated, diverging from umbo; 1 strong and vertical; 3b thick, anterodorsally inclined. Angle between 1 and 3b ca. 70°. Left valve dentition unknown. Anterior adductor muscle scar weak, elongated along pallial line, around twice as long as wide, not detached. Posterior adductor muscle scar weak, rounded. Pallial line weak, entire. Remarks. We compare our specimens with Pseudotrapezium groenlandicum Spath, 1936, from Milne Land, East Greenland (Spath 1936) due to their thick hinge plate, similar cardinal dentition and external shape. However, the Svalbard specimens are much smaller and more thin shelled than the Greenland material, so we are not entirely sure they represent the same species and leave them in open nomenclature. Fürsich (1982) moved P. groenlandicum into the genus Hartwellia Kitchin, 1926, and redescribed it as Hartwellia (H.) groenlandica. Hartwellia was considered by Cox ...