Isotriphora leo, 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 : 16-18

Isotriphora leo sp. nov.

urn:lsid:zoobank.org:act:D7BFF5C6-9436-4BA3-BE0F-8551DCB43F8A

Figs 5 , 23D , 52

Diagnosis

Small shell with a truncated apex; late adapical spiral cord, emerging in the third whorl of shell; white color, but light brown in the adapical spiral, subperipheral and adapical basal cords.

Etymology

The specific name alludes to the lion ( Panthera leo (Linnaeus, 1758)) owing to the habit of authors to name species of Isotriphora after big felines.

Material examined

Holotype

BRAZIL – Trindade Island • Beberibe; depth 4–6 m; Barcellos and Laurino leg.; MNRJ 29392 *.

Other material

BRAZIL – Trindade Island • 1 spec.; same collection data as for holotype; Barcellos and Laurino leg.; MORG 25615 * • 2 specs; Fundeadouro ; depth 15 m; 15 Sep. 1987; Barcellos and Laurino leg.; MORG 25645 *.

Description

Shell sinistral, small, cyrtoconoid to ovoid, slightly convex profile, up to 2.4 mm long, 0.9 mm wide, length/width ratio 2.4 to 2.5, up to 7.5 whorls. Protoconch paucispiral with truncated apex, without clear differentiation from teleoconch; two strongly nodulose spiral cords (median and abapical) of equal size starting from slightly pointed and very narrow nucleus, respectively situated at ~34% and ~71% of whorl height; third (adapical) spiral cord evident since third whorl of shell, bordering median cord and reaching same size of other cords after 1.5 to two whorls, being usually slightly more prominent than others on body whorl; on body whorl, spiral cords are 1.0–1.2 × as wide as distance between them; 17– 20 axial ribs at sixth whorl of shell, with varying arrangement, often orthocline, but slightly prosocline or slightly opisthocline in some whorls of certain shells; rounded nodules of medium to moderately large size; distinct and well-developed suture, with small sutural cord; smooth subperipheral and basal cords, abapical one very reduced, even indistinct in some shells; supranumerical cords absent; ovate to elliptical aperture, 0.34–0.57 mm long, 0.31–0.43 mm wide, length/width ratio 1.1–1.4; anterior canal very short, open, 0.08–0.14 mm long, 0.13–0.14 mm wide, length/width ratio 0.6–1.0; posterior canal as acute sinus, 0.07–0.12 mm long, not detached from aperture. Shell white, but light brown in the adapical spiral, subperipheral and adapical basal cords.

Remarks

This species is unique in Isotriphora by the late emergence of the adapical spiral cord of the teleoconch ( Fig. 5 E–F), thus raising doubts about the generic allocation. In fact, the shell of Isotriphora leo sp. nov. is very similar to that of some species of the family Cerithiopsidae in shape, small size and the late development of the adapical spiral cord, constituting an example of convergence in Triphoroidea .

The late emergence of the adapical spiral cord distinguishes I. leo sp. nov. from the also small and slightly ovoid shell of I. uncia sp. nov. from Fernando de Noronha and Atol das Rocas, and the similarly colored shell of Isotriphora tigrina Fernandes, Pimenta & Leal, 2013 from the Vitória-Trindade Chain. Isotriphora leo sp. nov. probably is restricted to the shallow waters of Trindade Island, as it was not sampled in deeper waters of the Vitória-Trindade Chain by expeditions MD55 and REVIZEE- Central ( Fernandes et al. 2013).

Geographical records

Brazil: Trindade Island.

Bathymetric distribution

Depth: 4– 15 m.

Figures

Fig. 5. Isotriphora leo sp. nov. A. MNRJ 29392*, holotype, 2.39 mm. B. MORG 25615*, 2.00 mm. C–D. MORG 25645*, 1.76 mm and 1.79 mm, respectively. E–I. HolotypE. Scale bars: A–E = 1 mm; F–G = 100 µm; H–I = 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. 52. Distribution map of Isotriphora sp. 1 (gray circle) and Isotriphora leo sp. nov. (red circle).