Mesosaccella rogovi Hryniewicz & Little & Nakrem 2014, sp. nov.

• Main Authors: Hryniewicz, Krzysztof, Little, Crispin T. S., Nakrem, Hans Arne
• Format: Other/Unknown Material
• Language: unknown
• Published: Zenodo 2014
• Subjects: Biodiversity; Taxonomy; Animalia; Mollusca; Bivalvia; Nuculanida; Malletiidae; Mesosaccella; Mesosaccella rogovi; Arctic; Knorringfjellet; Spitsbergen
• Online Access: https://doi.org/10.5281/zenodo.4929773; http://treatment.plazi.org/id/A2311D4D9F16E33704E6FB78FC462BD6

Mesosaccella rogovi sp. nov. (Figures 5 R–T, 7 A–F) 2011 Malletiid sp. 1—Hammer et al ., fig. 7n–o, tab. 2. Etymology. After Mikhail A. Rogov, Russian palaeontologist specializing in Jurassic stratigraphy of the Arctic. Type locality. Seep 9, Knorringfjellet, Spitsbergen, 78°18’49.9”N 16°10’58.9”E. Type material. Holotype: PMO 224.971; a well preserved left valve showing the shape and characteristic ornament of posterodorsal margin. Paratypes: PMO 217.229; a partially preserved articulated internal mould showing anterior adductor muscle scar, posterior adductor muscle scar and weak pallial line. PMO 217.371; a well preserved articulated internal mould with fragments of shell, which shows weak ridges formed by growth line deflections, a carina and lancet-shaped escutcheon; the mould shows the pallial line and weak imprints of the external ridges. PMO 217.539; a partial right valve with cardinal area showing continuous tooth row. Material examined. 89 specimens, mostly articulated valves or internal moulds with portions of the shell remaining. See Appendix 1 for the list of specimens. Diagnosis. Elongated, lancet-shaped species with posterior part more than four times the length of the anterior part. Up to three weak posterior ridges formed by growth line deflections on the posterior part of the shell. A carina subparallel to the posterodorsal margin runs from the umbo to the posterior shell extremity. Dimensions. 3.5–23 mm in length, 1.2–9.1 mm in height, 1–8.2 mm in width. See Figure 8 A–D and Appendix 2D for details. Description . Medium to large, up to 23 mm long, 9.1 mm high and 8.2 mm wide, elongated (H/L≈0.42), lancet-shaped, weakly inflated (W/L≈0.32, W/H≈0.77); greatest height and width around medial plane. Elongated shape especially well expressed in posterior part, which occupies around 80% of total length (Pl/L≈0.79). Shell shape parameters remain relatively constant throughout ontogeny. External ornament of narrowly-spaced, commarginal growth lines, strongest in median part of shell and weaker towards ...