Microgloma mirmidina (Dautzenberg & Fischer, 1897)

Benaim, Natalia Pereira & Absalao, Ricardo Silva, 2011, Microgloma Sanders & Allen, 1973 (Nuculanidae) and Pristigloma Dall, 1900 (Pristiglomidae) (Pelecypoda) in the Campos Basin of Brazil, ZooKeys 152, pp. 1-20 : 7-9

Microgloma mirmidina (Dautzenberg & Fischer, 1897) Figs 9-13

Leda mirmidina Dautzenberg & Fischer, 1897: 208, pl. 6, figs 11-14; Dautzenberg 1927: 292, pl. 8, figs 27-30.

Nuculana mirmidina : Clarke 1962: 53.

Microgloma mirmidina : La Perna 2008: 154, 155, fig 6.

Geographical distribution.

Southeast of Flores, Azores, 1846 m ( La Perna 2008). Campos Basin 1050-1950 m (present study).

Material examined.

MNRJ 19115 (#68, 2003), 6 valves; MZSP 99978 (#71, 2003), 7 valves; IBUFRJ 15889 (#67, 2003), 5 valves; IBUFRJ 17501 (#87, 2003), 4 valves; IBUFRJ 19084 (# 10, 2001), 4 valves; IBUFRJ 19085 (# 28, 2001), 1 valve; IBUFRJ 19086 (# 42, 2002), 1 valve; IBUFRJ 19087 (# 48, 2002), 6 valves and 2 specimens; IBUFRJ 19088 (# 51, 2002), 1 valve; IBUFRJ 19089 (# 53, 2002), 6 valves and 1 specimen; IBUFRJ 19090 (# 57, 2002), 1 valve IBUFRJ 19091 (# 62, 2002), 4 valves; IBUFRJ 19092 (# 63, 2002), 10 valves; IBUFRJ 19093 (# 68, 2002), 1 valve; IBUFRJ 19094 (# 73, 2002), 6 valves and 1 specimen; IBUFRJ 19095 (# 75, 2002), 1 valve; IBUFRJ 19096 (# 77, 2002), 12 valves and 1 specimen; IBUFRJ 19097 (# 78, 2002), 4 valves; IBUFRJ 19098 (# 81, 2002), 2 valves; IBUFRJ 19098 (# 81, 2002), 2 valves; IBUFRJ 19099 (# 83, 2002), 4 valves and 1 specimen; IBUFRJ 19100 (# 85, 2002), 1 valve; IBUFRJ 19101 (# 86, 2002), 6 valves; IBUFRJ 19102 (# 87, 2002), 5 valves; IBUFRJ 19103 (# 50A, 2003), 1 valve; IBUFRJ 19105 (# 61, 2003), 3 valves; IBUFRJ 19106 (# 63, 2003), 2 valves; IBUFRJ 19107 (# 72, 2003), 2 valves and 1 specimen; IBUFRJ 19108 (# 73, 2003), 4 valves; IBUFRJ 19109 (# 77, 2003), 5 valves and 3 specimens; IBUFRJ 19110 (# 78, 2003), 4 valves; IBUFRJ 19111 (# 82, 2003), 2 valves; IBUFRJ 19112 (# 84, 2003), 2 valves; IBUFRJ 19113 (# 86, 2003), 2 valves; IBUFRJ 19114 (# C10, 2008), 1 valve.

Characterization.

Shell H/L approximately 0.79 (n 10, min 0.75, max 0.83), W/H approx. 0.59(n 10, min 0.53, max 0.63). Posterior part of the hinge plate shorter than anterior one. Width of both the anterior and posterior rows of teeth occupies nearly half of the width of the hinge plate, which is moderately thick for its size (whp/H about 0.11). Prodissoconch smooth, length approximately 176 µm.

Remarks.

The radial sculpture on the prodissoconch surface is absent in Microgloma mirmidina , but admittedly it is not always clearly developed in the other species of Microgloma ( La Perna 2008). Microgloma mirmidina differs from other species of the genus in the elongated outline, more inflated shells and small hinge plate. In relation to the type material of Microgloma mirmidina figured by La Perna (2008) the Campos Basin material presents a smaller hinge plate. The figured specimens presents H/L ratio of 0.72, 0.76 and 0.83 ( La Perna 2008 fig 6 B, E, I, respectively). Despite geographical distance between the two records of the present species, these conchological differences are not pronounced enough to affirm they belong to distinct species.