Scissurella maraisorum, Geiger, Daniel L., 2006

Geiger, Daniel L., 2006, Eight new species of Scissurellidae and Anatomidae (Mollusca: Gastropoda: Vetigastropoda) from around the world, with discussion of two new senior synonyms, Zootaxa 1128, pp. 1-33 : 10-14

Scissurella maraisorum new species: Figures 7–8

Type material. Holotype ( NMSA W3498/T1616: Fig. 7 ). Paratypes ( NMSA W3499/ T1617, 2). Paratypes (Coll. A & J.P. Marais, 3: including Fig. 8 A). Paratypes ( SBMNH 359327, 2. Fig. 8 B. SBMNH 359324: Fig. 8 C). Unfigured paratypes (AMS C.447877, 1; BMNH 20050274, 1; MNHN type collection, 1; UMUT RM29043, 1; USNM 1081939, 1).

Type locality. 20 m, Aliwal Shoal, Kwazulu­Natal south coast, Republic of South Africa. June 2003. 30.250°S, 30.817°E.

Etymology. Named after Dr. Johan P. and Alwyn P. Marais of South Africa, who collected the specimens and generously made them available for study, and for their continuing accomplishments to further the understanding the South African malacofauna. Genitive masculine plural of surname.

Description. Shell small (to 0.72 mm: holotype), trochiform depressed. Protoconch of 1 whorl, fine axial sculpture with median ridge, no apertural varix, apertural margin convex. Teleoconch I of 1–1.125 whorls, approximately 14–18 strong axial cords, no spirals, interstices with fine irregular axials. Teleoconch II of 0.33 whorls. Shoulder flat, suture deep, near suture indistinct axial cords of same spacing as on teleoconch I, mainly fine irregular axials. Base with strong axial cords of same spacing as on teleoconch I from selenizone to lowermost base, fading towards umbilicus; no spirals; interstices with fine irregular axials; base continuously sloping with umbilical wall. Umbilicus wide, open, protoconch visible through umbilicus. Selenizone above periphery, keels moderately strongly elevated, strong, inclined approximately 45° towards coiling axis. Aperture subquadratic, adumbilical wall straight, roof almost straight, base curved with adumbilical projection.

Differential diagnosis. Scissurella maraisorum is characterized among the African species by its flat spire, the absence of spiral sculpture, and the widely open umbilicus which shows the lower surface of the protoconch. Scissurella jucunda Smith, 1890 from South Africa has a distinctly elevated spire, a closed umbilicus, and some spiral sculpture on shoulder as well as base. Scissurella rota Yaron, 1983 from East Africa has spirals on shoulder and base, the umbilicus is bordered by an edge towards base. Scissurella sudanica Bandel, 1998 from East Africa has an elevated spire, spirals on shoulder and base, and a narrower umbilicus that is bordered by a strong cord towards the base. Sinezone doliolum Herbert, 1986 from South Africa has the slit closed to a foramen in adults, has an elevated spire, has indistinct spirals on shoulder and base, and an almost closed umbilicus. Sinezona insignis (Smith, 1890) from South Africa has a closed foramen in adults, fewer but stronger axial cords to low lamellae, has strong axials on the protoconch, and has a much more narrow umbilicus bordered by a cord towards base. Sukashitrochus maraisi Herbert, 1986 from South Africa has distinct spiral keels on base, a closed foramen in mature specimens, and the umbilicus is bordered by a keel.

Distribution. Known from type locality only.

Sinezona garciai new species: Figures 9–10

Type material. Holotype ( USNM 1081940: ex UMML 30.12043. Fig. 9 ). Paratypes ( SBMNH 359317, 2: ex UMML 30.12043. Fig. 10 A, B), same data as holotype. Paratype ( UMML 30.12043, 1), same data as holotype. Paratype: 16 m, St. Croix, US Virgin Islnads, 17.800°N, 64.800°W ( UMML 30.12051, 1. Fig. 10 C).

Type locality. 1.5 m, behind outer reef, Courtown Cays, San Andres y Providencia, Colombia, 12.383°N, 81.433°W.

Etymology. Named for Emilio Garcia of Lafayette, Louisiana, USA, for his continuing contribution to the knowledge of the Caribbean malacofauna, and his generous support of ongoing research.

Description. Shell small (to 0.76 mm), trochiform depressed, last 0.125 whorl distinctly descending. Protoconch of one whorl, fine, sharp axials in outer half of whorl, inner half smooth, no apertural varix, apertural margin convex. Teleoconch I of 0.66 whorls. Shoulder slightly convex, suture distinct; approximately 10–12 axial cords, no spirals, interstices with fine irregular growth marks. Teleoconch II of 0.66 whorls, same density and strength of axials as on teleoconch I, onset of broad, low axial cords slightly after onset of selenizone, increasing in number to approximately 10–12, somewhat unevenly spaced. Base with distinct constriction below selenizoen, same density of more distinct axial cords as on shoulder, crossed by approximately 16–18 weaker spiral cords, cords mirror increase in strength and number with growth to those on shoulder. Selenizone above periphery, keels strong, moderately elevated, growth marks very distinct; foramen elongated. Umbilicus wide, bordered by strong spiral cord, walls straight, with fine axial growth marks. Aperture obliquely D­shaped, roof overhanging. Animal unknown.

Differential diagnosis. Sinezona confusa Rolán & Luque, 1994 [= Sin. columbiana ( Bandel, 1998) ] from the Caribbean has a more elevated overall shape and spire, a very narrow, barely open umbilicus, and a protoconch with fewer and broader axials as well as an apertural varix. Scissurella electilis Montouchet, 1972 from Brazil has a much narrow umbilicus, lacks the strong cord separating the umbilicus from the base, and retains an open slit at maturity. Satondella brasiliensis (Mattar, 1987) [= Sat. tabulata (Watson, 1886) ?] from Brazil and Sat. tabulata from the Caribbean have a more strongly descending aperture on the last quarter whorl and the foramen is drawn out into a strongly elevated chimney. Satondella tabulata has microhexagonal microsculpture, which is often eroded and looks smooth; the protoconch sculpture of the nominal taxon Sat. brasiliensis is unknown.

Distribution. Colombia to Bahamas.

Specimen Records. 18 m, Samphire Cay, NW Nassau, Bahamas, 25.183°N, 77.017°W (HLC, 1).

Remarks. Sinezona garciai is considered distinct from Sin. confusa , and not simply a form with more depressed shells. All five specimens of Sin. garciai available show highly congruent features with very little intraspecific variability. The same applies to 68 lots of Sin. confusa inspected ranging from Bermuda to Venezuela.

Sinezona columbiana is a synonym of Sin. confusa , showing all features of that species, which also distinguish it from Sin. garciai : overall more elevated shell, more narrow umbilicus, and a protoconch with fewer and broader axials as well as an apertural varix.

Figures

FIGURE 7. Holotype of Scissurella maraisorum new species (NMSA W 3498 / T 1616). Aliwal Shoal, Kwazulu­Natal south coast, SCUBA 20 m. June 2003. 30.250 ° S 30.817 ° E. Uncoated specimens, variable pressure, VPSE detector. Scale bar shell = 500 µm. Scale bar protoconch = 100 µm.

FIGURE 8. Paratypes of Scissurella maraisorum new species. A. Collection J. P. & A. P. Marais, South Africa. B. (SBMNH 359327). C. (SBMNH 359324). All specimens from Aliwal, Kwazulu­ Natal south coast, SCUBA 20 m. June 2003. 30.250 ° S 30.817 ° E. Uncoated specimens, variable pressure, VPSE detector. Scale bars shell = 200 µm. Scale bars protoconch = 100 µm.

FIGURE 9. Holotype of Sinezona garciai new species. Behind outer reef, Courtown Cays, W. Caribbean, Colombia, 12.383 ° N, 81.433 ° W (USNM 1081940: ex UMML 30.12043). Scale bar shell = 500 µm. Scale bar protoconch = 100 µm.

FIGURE 10. Paratypes of Sinezona garciai new species. A­B. 1.5 m, Behind outer reef, Courtown Cays, W. Caribbean, Colombia, 12.383 ° N, 81.433 ° W (SBMNH 359317: ex. UMML 30.12043). C. 16 m, St. Croix, 17.800 ° N, 64.800 ° W (UMML 30.12051). Scale bars shell = 500 µm. Scale bars protoconch = 100 µm.