Philobrya quadrata

• Main Authors: Urcola, Matias Ricardo, Zelaya, Diego Gabriel
• Format: Other/Unknown Material
• Language: unknown
• Published: Zenodo 2024
• Subjects: Biodiversity; Taxonomy; Animalia; Mollusca; Bivalvia; Arcida; Philobryidae; Philobrya; Philobrya quadrata; Antarc*; Antarctic
• Online Access: https://doi.org/10.5281/zenodo.10994139; http://treatment.plazi.org/id/A279878B741CD21DF5EAE041FB4DFBEA

Philobrya quadrata (Pfeffer, 1886) (Figure 15) Philippiella quadrata Pfeffer in Martens & Pfeffer, 1886: 119, 120, pl. 4, figs. 6a, b. Philobrya quadrata. Dell 1964: 167, 168, text fig. 2.6. Philippiella ungulata. Pfeffer in Martens & Pfeffer, 1886: 120, 121, pl. 4, fig. 7; Soot-Ryen, 1951: 11. Type locality: South Georgia, 54°30’S 35°50’W, 94 m [here restricted]. Material examined: South Georgia: 54°30’S 35°50’W, 94 m (MACN-In 44471: Neotype, here designated; MACN-In 44472: 1 spec). Burdwood Bank: 54°16.67’S 59°57.79’W, 96 m (MACN-In 44473: 2 spec, 2 v); 54°23.32’S 59°41.18’W, 65 m (MACN-In 44474: 7 spec, 4 v); 54°24.21’S 59°32.49’W, 86 m (MACN-In 44475: 6 spec, 7 v). Distribution: Only known with certainty from South Georgia (Pfeffer in Martens & Pfeffer 1886; Soot-Ryen, 1951; Dell 1964; this study) and Burdwood Bank (this study); 18‒ 94 m. Philobrya quadrata was also mentioned from some other sub-Antarctic and Antarctic localities, although the identity of this material deserves further studies (see Remarks section). Description: Shell small (maximum L = 5.3 mm), ovate, high ( H/L = 0.93 ± 0.04, n = 10), compressed ( W/H = 0.56 ± 0.06, n = 10), delicate; with a narrow, depressed dorsal slope. Umbo bluntly pointed, located at anterior end, only slightly outstanding from shell outline in smaller specimens but prominent, bluntly pointed and recurved in larger specimens. Umbonal angle: 85‒95° (n = 11). Dorsal margin with the anterior portion long, vertically straight to somewhat arched, and the posterior portion flatted to curved, forming a continuous curve with the posterior margin. Ventral margin almost straight in small-sized specimens to markedly sinuate in larger specimens. Prodissoconch D-shaped, with posterior end higher than anterior end, widely projected ventrally, of 315‒385 µm Lp (n = 4), raised from dissoconch. Antero-dorsal and postero-dorsal areas raised, sculptured with densely packed commarginal folds. Central area sculptured with microscopic, ovate pits, forming quincuncial pattern. ...