Microgloma nhanduti, Benaim, Natalia Pereira & Absalao, Ricardo Silva, 2011

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 : 12-14

Microgloma nhanduti sp. n. Figs 2331

Holotype.

MNRJ 19.113 (Figs 26, 28).

Type locality.

Campos Basin, #54, 12/12/2002, 750m, 21°57'17,5"S, 39°56'01,1"W.

Paratypes.

IBUFRJ 14991 (# 54, 2002), 2 valves and 1 specimen; IBUFRJ 19176 (# 64, 2003), 1 specimen; MZSP 99980 (# 54, 2002), 5 valves; USNM 1156944 (# 54, 2002), 5 valves; MNHN 24597 (# 54, 2002), 2 valves 1 specimen.

Etymology.

Nhanduti is a Tupi–Guarani term (the language spoken by the largest groups of native people living in Brazil prior to the European colonization) for a spider web–like structure, similar to those present on the prodissoconch of this species. The species epithet is proposed as a noun in apposition.

Material examined.

IBUFRJ 15140 (# 69, 2002), 17 valves and 2 specimens; IBUFRJ 15283 (# 69, 2002), 6 valves; IBUFRJ 19115 (# 33, 2002), 1 valve; IBUFRJ 19116 (# 64, 2002), 16 valves and 1 specimen; IBUFRJ 19117, (# 49, 2003), 7 valves; IBUFRJ 19118, (# 54, 2003), 1 valve; IBUFRJ 19119, (# 59, 2003), 10 valves and 2 specimens; IBUFRJ 19121, (# 34, 2002), 1 valve; IBUFRJ 19122, (# 37, 2002), 1 valve; IBUFRJ 19123, (# 38, 2002), 1 valve; IBUFRJ 19124, (# 64, 2003), 12 valves and 1 specimen; IBUFRJ 19125, (# 75, 2003), 2 valves; IBUFRJ 19126, (# A7, 2008), 4 specimens; IBUFRJ 19127, (# A7, 2008), 1 valve; IBUFRJ 19128, (# A7, 2008), 1 valve and 3 specimens; IBUFRJ 19129, (# D7, 2008), 1 specimen; IBUFRJ 19130 (# H7, 2008), 2 specimens; IBUFRJ 19131 (# D6, 2008), 3 specimens; IBUFRJ 19132 (# H7, 2008), 1 specimen; IBUFRJ 19133 (# H7, 2008), 4 valves; IBUFRJ 19134 (# D6, 2008), 1 specimen; IBUFRJ 19135 (# I7, 2008), 1 specimen; IBUFRJ 19136 (# A7, 2009), 2 specimens; IBUFRJ 19137 (# A7, 2009), 6 specimens; IBUFRJ 19138 (# D6, 2009), 4 specimens; IBUFRJ 19139 (# H7, 2009), 10 specimens; IBUFRJ 19140 (# CANAC7, 2009), 5 specimens and 2 valves; IBUFRJ 19141(# CANAC7, 2008), 1 specimen; IBUFRJ 19142 (# I7, 2008), 2 specimens; IBUFRJ 19143 (# CANAC7, 2008), 6 specimens; IBUFRJ 19144 (# D7, 2008), 1 specimen.

Diagnosis.

Shell minute, ovate. Entire margin slightly thickened. Hinge plate moderately thick. Prodissoconch with web–like striae.

Description.

Shell minute, ovate, H/L ratio about 0.78 (n 29, min 0.74, max 0.81), Width of both valves/H ratio about 0.7 (n 11, min 0.67, max 0.77), inequilateral, translucent, glossy; umbones moderately prominent, large, posterior to midline, orthogyrous. Antero–dorsal margin convex and oblique; anterior margin rounded and projected. Antero–ventral margin convex, postero–ventral margin shorter and rising up to short and rounded posterior end; postero–dorsal margin convex, but forming a small shoulder. Entire shell margin slightly thickened. Surface with subtle commarginal growth lines. Hinge plate with 5-7 anterior and 4-5 posterior teeth, interrupted by a shallow rectangular hinge plate. Width of both anterior and posterior row of teeth occupies about 70% of width of hinge plate, which is thick for its size (whp/H approximately 0.14). Posterior part of the hinge plate shorter than anterior one. Prodissoconch surface nacreous, with several radial striae, resembling a spider’s web. Prodissoconch length approximately 246 µm.Maximum adult shell length 1.16 mm.

Remarks.

Microgloma nhanduti sp. n. is similar to Microgloma pusilla and Microgloma tumidula in the oval outline. but has more prominent umbones (Figs 26-28). Compared to Microgloma macaron sp. n. and Microgloma yongei , Microgloma nhanduti sp. n. has a more elongated outline, a longer anterior area, and a more evident prodissoconch sculpture, with a web–like pattern (Figs 29-30). In Microgloma nhanduti sp. n. the umbo is not as prominent and the shell margin not as thick as in Microgloma macaron sp. n.Untill now this species is reccorded solely in Campos Basin.