Isotriphora uncia, Fernandes & Pimenta, 2020

Fernandes, Maurício Romulo & Pimenta, Alexandre Dias, 2020, Unraveling one of the ‘ Big Five’: update of the taxonomy of Triphoridae (Gastropoda, Triphoroidea) from Brazil, European Journal of Taxonomy 665 (665), pp. 1-170 : 14-16

Isotriphora uncia sp. nov.

urn:lsid:zoobank.org:act:2D9B275B-0251-48C5-A192-61FD1A16B0BE

Figs 4 , 23H , 51

Diagnosis

Small, white shell; truncated apex; median spiral cord (or supranumerical cord) emerges in the ninth/ eleventh whorl of the shell; closed anterior canal.

Etymology

The specific name alludes to the snow leopard ( Panthera uncia (Schreber, 1775)) owing to the white shell color and the habit of authors to name species of Isotriphora after big felines.

Material examined

Holotype

BRAZIL – Fernando de Noronha Archipelago • Ilha Rata; depth 12 m; 8 Jul. 1999; IBUFRJ 11165 .

Other material

BRAZIL – Fernando de Noronha Archipelago • 1 spec.; same collection data as for holotype; MNRJ 34420 * • 2 specs; Baía Sueste ; depth 17 m; Jan. 1979; MORG 20632 * • 1 spec.; Cabeço da Sapata ; depth 40 m; 5 Dec. 1985; M. Cabeda leg.; MORG 24622 * • 2 specs; Cabeço da Sapata ; depth 40 m; 5 Dec. 1985; M. Cabeda leg.; MORG 52610 *. – Atol das Rocas • 30 specs; Ilha do Farol ; Feb. 1977; MORG 19120 * • 8 specs; Feb. 1977; on coral; MORG 19137 *.

Description

Shell sinistral, small, cyrtoconoid or slightly ovoid, nearly rectilinear to moderately convex profile, up to 3.7 mm long, 1.2 mm wide, length/width ratio 2.4 to 3.0 up to 10.5 whorls. Protoconch paucispiral with truncated apex, without clear differentiation from teleoconch; two strongly nodulose spiral cords starting from slightly pointed and very narrow nucleus, abapical cord initially much more prominent; adapical cord usually more prominent than abapical one in the body whorl of adult shells; median spiral cord (or just supranumerical cord) emerges in ninth to eleventh whorl of shell, bordering closely adapical cord; on body whorl, spiral cords are 1.3–2.3 × as wide as the distance between them; 14–17 nearly orthocline (initial whorls) to opisthocline (late whorls), weak axial ribs at the seventh whorl of shell; rounded nodules of medium to moderately large size; distinct but very shallow suture, with small sutural cord, more evident in late whorls; thin, slightly wavy to nearly smooth subperipheral cord, not developing nodules, one to two very small and ill-defined basal cords; supranumerical cords apparently absent; small and ovate aperture, 0.54–0.62 mm long, 0.43–0.44 mm wide, length/width ratio 1.2–1.4; anterior canal closed, medium-sized, curved backwards/downwards, 0.27–0.37 mm long, 0.25–0.27 mm wide, length/width ratio 1.1–1.3; posterior canal as somewhat deep sinus, 0.12–0.14 mm long, not detached from aperture. Shell white.

Remarks

This is one of the smallest triphorids in the world, with the largest adult shell herein analysed reaching only 3.7 mm in length. The species is abundant in Fernando de Noronha and Atol das Rocas, but shells are often much eroded, especially at the apex.

Isotriphora guanahacabibes Rolán & Fernández-Garcés, 2008 , up to now restricted to Cuba and Cayman Islands, shares similar features with I. uncia sp. nov., including the white shell and late development of the median spiral cord. In contrast, the shell of I. guanahacabibes reaches up to 5.5 mm in length and it is more elongated and slightly bottle-shaped ( Rolán & Fernández-Garcés 2008), instead of the short and usually slightly ovoid shell of I. uncia sp. nov. ( Fig. 4C ).

The median spiral cord of the teleoconch of I. uncia sp. nov. is not fully developed in shells herein analysed, appearing as a very small thread just behind the peristome ( Fig. 4G ), which raises the hypothesis of it to be merely a supranumerical cord. However, other species of Isotriphora also show a very late development of this median spiral cord ( Rolán & Fernández-Garcés 2008; Fernandes et al. 2013), suggesting that a shell of I. uncia sp. nov. attaining more whorls would reveal a gradual development of the median spiral cord.

Geographical records

Brazil: Fernando de Noronha and Atol das Rocas.

Bathymetric distribution

Depth: 12– 40 m.

Figures

Fig. 4. Isotriphora uncia sp. nov. A. IBUFRJ 11165, holotype, 2.37 mm. B. MORG 24622*, 3.63 mm. C. MORG 19137*, 2.50 mm. D, F–H. Same shell as A. E. MORG 20632*. Scale bars: A–D = 1 mm; E, H = 100 µm; F–G = 500 µm.

Fig. 23. Triphoridae from Brazil (2). A. “Inella” sp. 4. B. Iniforis carmelae Rolán & Fernández- Garcés, 1993. C. Iniforis pseudothomae Rolán & Fernández-Garcés, 1993. D. Isotriphora leo sp. nov. E. Isotriphora onca Fernandes, Pimenta & Leal, 2013. F. Isotriphora tigrina Fernandes, Pimenta & Leal, 2013. G. Isotriphora tricingulata Rolán & Fernández-Garcés, 2015. H. Isotriphora uncia sp. nov. I. Isotriphora sp. 1. J. Latitriphora albida (A. Adams, 1854). K. Marshallora sp. L. Marshallora ostenta Rolán & Fernández-Garcés, 2008. M. Marshallora sp. 1. N. Monophorus caracca (Dall, 1927) comb. nov. O. Monophorus olivaceus (Dall, 1889). P. Monophorus verecundus sp. nov. Q. Nanaphora leei Fernandes & Pimenta, 2015. R. Nanaphora verbernei (Moolenbeek & Faber, 1989). S. Nanaphora sp. 1. Scale bars: 1 mm.

Fig. 51. Distribution map of Isotriphora uncia sp. nov. (red circle = type locality; black circle = additional locality) and Isotriphora tigrina Fernandes, Pimenta & Leal, 2013 (brown circle = type locality; gray circle = additional locality).