Monophorus verecundus, 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 : 27-29

Monophorus verecundus sp. nov.

urn:lsid:zoobank.org:act:7A1A8226-038E-4623-8F73-9420F12B7848

Figs 11 , 23P , 57 , 83

Diagnosis

Embryonic shell covered by micro-spiral threads; larval shell initially with two spiral cords, but adapical cord disappears after 0.5 to 0.75 whorl; teleoconch with brown internodular spaces, especially in the adapical spiral cord.

Etymology

The name is derived from the Latin ‘ verecundus ’, meaning ‘shy, bashful’, and referring to the scarce records of this species even after an extensive revision.

Material examined

Holotype

BRAZIL – Rio de Janeiro • 23º12′04″ S, 40º59′42″ W, HAB 16-B5; depth 141 m; 2 Jul. 2009; MNRJ 18383 *.

Other material

BRAZIL – Rio Grande do Norte • 1 spec.; 04º44′53″ S, 36º25′27″ W; depth 102–108 m; 23 May 2011; MNRJ 35114 *. – Rio de Janeiro • 1 spec.; 22º42′ S, 40º40′ W; depth 110–120 m; 11 Apr. 2003; MNRJ 19479 *. – São Paulo • 1 spec.; PADCT st. 6577; MNRJ 27843 *.

Description

Shell sinistral, elongated, cyrtoconoid, slightly convex profile, up to 5.4 mm long, 1.4 mm wide, length/ width ratio 3.3 to 4.0. Protoconch multispiral, conical/columnar, 4.5–5 keeled-shaped whorls, 0.49– 0.52 mm long, 0.37–0.40 mm wide; embryonic shell dome-shaped, covered by about 10–12 micro-spiral threads, each composed of granules usually with somewhat pointed profile; larval shell initially with two spiral cords, but adapical cord disappears after 0.5 to 0.75 whorl, remaining abapical cord extends to end of protoconch, situated at ~46%–53% of last whorl height; ~27 slightly sigmoid axial ribs. Teleoconch with up to 11 whorls; two spiral cords (adapical and abapical) at beginning, abapical one continuous to that of protoconch, adapical cord can be slightly larger than abapical one in early whorls; median spiral cord emerges at beginning of third to beginning of fifth whorl, reaching same size of other cords after two to 2.5 whorls; on body whorl, distance between spiral cords is equal or up to 1.2 × higher than width of cords; 17–19 nearly orthocline axial ribs; rounded to elliptical (especially in median and abapical spiral cords) nodules of medium size; distinct, well-developed suture, with small sutural cord; subperipheral and adapical basal cords narrow and nodulose, wavy abapical basal cord; two apparent supranumerical cords emerge near peristome, one between median and abapical spiral cords, the other between abapical and subperipheral cords; ovate aperture, 0.70 mm long, 0.49 mm wide, length/width ratio 1.4; partly closed anterior canal, crossed in its base by projection of outer lip, 0.26 mm long, 0.21 mm wide, length/ width ratio 1.2; deep posterior canal, up to 0.29 mm long, almost detached from aperture. Light brown protoconch; teleoconch with cream background, brown internodular spaces, especially in adapical spiral cord and in abapical whorls; whitened nodules.

Remarks

This species has a color pattern similar to that of Similiphora intermedia (C.B. Adams, 1850) , but it is mainly distinguished by a protoconch with fewer whorls (4.5 to 5 whorls, Fig. 11I , vs ~6 whorls in S. intermedia ), the embryonic shell covered by micro-spiral threads ( Fig. 11 J–K, instead of granules in S. intermedia ), larval shell with one main spiral cord ( Fig. 11I , but two cords in S. intermedia ), and a different transition protoconch/teleoconch. Another species with a similar color pattern is Triphora scylla Fernandes & Pimenta, 2015 , but T. scylla is somewhat darker, possessing a larval shell with two spiral cords, a late median spiral cord of the teleoconch, and thicker subperipheral and basal cords ( Fernandes & Pimenta 2015).

The micro-spiral threads in the embryonic shell of M. verecundus sp. nov. ( Fig. 11 J–K) are similar to the cruciform granules often observed in this genus. Even though Monophorus is usually described as having two spiral cords in the larval shell (e.g., Marshall 1983), the type species Monophorus perversus shows a variation of one to two spiral cords ( Bouchet 1985), thus not being an impediment to the present generic allocation.

Geographical records

Brazil: Rio Grande do Norte, Rio de Janeiro, São Paulo.

Bathymetric distribution

Depth: 102– 141 m.

Figures

Fig. 11. Monophorus verecundus sp. nov. A. MNRJ 18383*, holotype, 4.24 mm. B. MNRJ 19479*, 5.40 mm. C. MNRJ 35114*, 2.47 mm. D, J. Same shell as C. E–I, K–L. Holotype. Scale bars: A–C, E = 1 mm; D, I, L = 100 µm; F–H = 500 µm; J–K = 50 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. 57. Distribution map of Monophorus caracca (Dall, 1927) comb. nov. (red circle = type locality; black circle = additional locality) and Monophorus verecundus sp. nov. (brown circle = type locality; gray circles = additional localities).

Fig. 83. Southern limits of planctotrophic, wide-range and tropical shallow-water triphorids from Brazil; the single exception is the lecithotrophic (but with a probable planctonic larva) Metaxia rugulosa (C.B. Adams, 1850). Illustrated shells are not necessarily from the southernmost end of their range. Species are cited from the left to the right, beginning with those situated at the top of each section: 1. Iniforis pseudothomae Rolán & Fernández-Garcés, 1993, Latitriphora albida (A. Adams, 1854), Triphora atlantica Smith, 1890, Triphora scylla Fernandes & Pimenta, 2015, Metaxia excelsa Faber & Moolenbeek, 1991, Cheirodonta dupliniana (Olsson, 1916), Coriophora novem (Nowell-Usticke, 1969), Cosmotriphora melanura (C.B. Adams, 1850), Eutriphora costai Fernandes & Pimenta, 2015, Marshallora ostenta Rolán & Fernández-Garcés, 2008. 2. Metaxia taeniolata (Dall, 1889), Monophorus verecundus sp. nov., Triphora elvirae De Jong & Coomans, 1988. 3. Metaxia rugulosa, Monophorus olivaceus (Dall, 1889), Sagenotriphora osclausum (Rolán & Fernández-Garcés, 1995), Strobiligera inaudita (Rolán & Lee, 2008). 4. Cosmotriphora arnoldoi Faber & Moolenbeek, 1991, Nanaphora verbernei (Moolenbeek & Faber, 1989), Nototriphora decorata (C.B. Adams, 1850), Triphora ellyae De Jong & Coomans, 1988, Similiphora intermedia (C.B.Adams, 1850). 5. Triphora charybdis Fernandes & Pimenta, 2015, Marshallora spp. Map adapted from Google Earth.