Monitilora sepes ( Barnard, 1964 )

Taylor, John D. & Glover, Emily A., 2018, Hanging on - lucinid bivalve survivors from the Paleocene and Eocene in the western Indian Ocean (Bivalvia: Lucinidae), Zoosystema 40 (7), pp. 123-142 : 136-138

Monitilora sepes ( Barnard, 1964)

( Fig. 8E-Q )

Phacoides sepes Barnard, 1964: 25 , fig. 6b.

Gonimyrtea sepes – Kilburn 1973: 701.

Monitilora sepes – Huber 2015: 445.

TYPE MATERIAL. — 3 syntypes ( SAM A9529 ) .

TYPE LOCALITY. — Off Morewood Cove, Natal, 27 fms (49 m).

MATERIAL EXAMINED. — Mozambique. Inhaca Island, Sud Ponta Abril , Expédition INHACA, 2011 stn MD17, 26°09.1’S, 32°58.0’E, 33 -39 m, 3 v, 01.12.2011 ( MNHN) . Inhaca Island, devant La Passe, Expédition INHACA, stn MD11, 26°04.8’S, 32°59’E, 24-32 m, 5 v, 30.XI.2011 ( MNHN) . Devant La Passe, stn MD15, 26°05.0’S, 32°59’E, 35 m, 5 v, 01.XII.2011 ( MNHN) .

South Madagascar. Expédition ATIMO VATAE, secteur de Lavanono, stn BP34, 25°25.8’S, 44°55.4’E, 14-15 m, 1 pv ( L 13.9 mm) ( MNHN).

DESCRIPTION

Shell white, subcircular, L to 15 mm, moderately inflated, light-shelled, posterior dorsal area shallowly demarcated. Sculpture of fine, low, closely spaced, commarginal lamellae, interspaces with radial riblets. Protoconch PI + PII = 264 µm, P II a narrow 17 µm rim ( Fig. 8Q ). Lunule short, scooped. Hinge plate narrow, RV with single small cardinal tooth and a small anterior lateral tooth, LV with two small cardinal teeth. the posteriormost longer and thinner, no lateral teeth. Anterior adductor scar medium length, detached for ½ of length, dorsal part much broader than ventral extension. Pallial line entire, shell margin smooth.

REMARKS

In the original description this species was poorly illustrated with only drawings of the hinge of one valve and a small portion of shell sculpture. It is therefore unsurprising that its affinities remained uncertain. The shell sculpture and hinge match with the shells from the Inhaca samples and placement in Monitilora can be confirmed. Huber’s (2015) generic assignment followed advice from present authors. The Mozambique and Natal records are distant from other recorded Monitilora species from eastern Australia, Philippines, Thailand and southern India and represent a considerable range extension for the genus. Apart from the eastern Australian M. ramsayi , shells are rarely present in museum collections.

Figures

FIG. 8. — Monitilora Iredale,1930, Palaeogene fossils (A-D) and Monitilora sepes (Barnard,1964) Inhaca,Mozambique (E-Q): A, B, Monitilora duponti (Cossmann, 1908) Paleocene, Danian, Calcaire de Mons, Mons Puits Coppée, Belgium (RBINS I.G. 6544), L 17.5 mm; C, D, Monitilora obliqua baudoni (Deshayes, 1857) Eocene, Lutetian, Amblainville, Oise, France, Chavan collection (RBINS I.G. 21.735), L 18 mm; E, F, Monililora sepes exterior and interior of left valve, Inhaca stn MD11, L 15 mm; G, H, exterior and interior of right valve, Inhaca stn MD15, L 12.1 mm; I, J, exterior and interior of right valve, Inhaca stn MD15, L 10.2 mm; K, L, exterior and interior of right valve, Inhaca stn MD15, L 10.1 mm; M, interior of left valve, Inhaca stn MD15, L 8.4 mm; N, O, detail of hinge teeth of left and right valves of H, I; P, detail of external sculpture of K; Q, protoconch of H. Scale bars: N, O, 1.0 mm; P, 500 µm; Q, 100 µm.