Marshallora sp. 1, Bouchet, 1985

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 : 23-25

Marshallora sp. 1

Figs 9 , 23M , 55

Material examined

BRAZIL – Rio de Janeiro • 2 specs; Rio das Ostras; Sep. 1971; MZSP 63331 *.

Description

Shell sinistral, elongated, cyrtoconoid, slightly convex profile, up to 4.0 mm long, 1.2 mm wide, length/ width ratio 3.2. Protoconch paucispiral, slightly globose but small, 2.25–2.5 convex whorls, 0.36– 0.47 mm long, 0.41–0.47 mm wide; first whorl dome-shaped and smooth, remaining whorls mainly smooth (maybe due to erosion), with one faint abapical cord or two distinct and equidistant spiral cords; small axial threads (or growth lines) may be present. Teleoconch with up to eight whorls; two spiral cords (adapical and abapical) at the beginning, abapical one continuous to that of the protoconch; median spiral cord emerges in the fifth whorl, reaching same size of other cords after 1.5 whorl; abapical cord initially larger, but the adapical one becoming the most prominent in abapical whorls; on the body whorl, the distance between spiral cords is 1.2 × higher than the width of cords; 19 nearly orthocline to slightly opisthocline axial ribs; rounded nodules of medium size; distinct, well-developed suture, with a small sutural cord; smooth subperipheral cord, two smooth and thick basal cords; no supranumerical cords; ovate aperture, 0.69 mm long, 0.61 mm wide, length/width ratio 1.1; open, short anterior canal, 0.24 mm long, 0.30 mm wide, length/width ratio 0.8; posterior canal is a very small notch, 0.15 mm long. Brown shell.

Remarks

Marshallora sp. 1 is similar to three Caribbean species with a paucispiral protoconch, Marshallora calva ( Faber & Moolenbeek, 1991) , Marshallora nicaraguensis Rolán & Luque, 1999 and the polychromatic Marshallora nichupte Rolán & Cruz-Ábrego, 1996 . The protoconch of M. calva bears a single spiral cord ( Faber & Moolenbeek 1991; Rolán & Fernández-Garcés 2008), but two cords appear in the juvenile shell of Marshallora sp. 1 (the protoconch of the adult shell is more similar to that of M. calva ), and the brown shell of M. calva can present whitened nodules, but not in Marshallora sp. 1 ( Fig. 9 A–B). Marshallora nicaraguensis bears two main spiral cords in the protoconch (similar to the juvenile shell of Marshallora sp. 1), although the subperipheral and adapical basal cords are slightly nodulose and the median spiral cord of the teleoconch emerges in the third/fourth whorl ( Rolán & Luque 1999), but in the fifth whorl in Marshallora sp. 1 ( Fig. 9C ). Marshallora nichupte has a smooth protoconch and the median spiral cord of the teleoconch emerging in the second to the fourth whorl ( Rolán & Cruz-Ábrego 1996), also earlier than in Marshallora sp. 1. Despite the similarities with those species, the absence of any other record of a lecithotrophic species of Marshallora in Brazil after the examination of thousands of lots suggests that a change to lecithotrophy occurred in an ancestral planctotrophic population in southeastern Brazil.

Geographical records

Brazil: Rio de Janeiro.

Bathymetric distribution

Only known from beach drift.

Figures

Fig. 9. Marshallora sp. 1. A–B. MZSP 63331*, 4.00 mm and 1.65 mm, respectively. C–I. Same shell as A. J. Same shell as B. Scale bars: A–C = 1 mm; D–F = 500 µm; G–H, J = 100 µm; I = 20 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. 55. Distribution map of Marshallora sp. 1.