Scissurella kaiserae, 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 : 2-6

Scissurella kaiserae new species: Figures 1–4

Type Material. Holotype ( SBMNH 348769: Fig. 1 ). Paratypes ( SBMNH 359438, 14: three shown in Figure 2 ), from type locality. Paratype (KLK, 1: 10–21 m, Roca Próspera Islet, Golfo de Chiriqui Coiba National Park, Panama, 7.776°N, 81.759°W. Fig. 2 A). Paratype (KLK, 1: 12–18 m, E side Lava Bay, Isla San Benedicto, Islas Revillagigedo, Mexico, 19.300°N, 110.790°W: Fig. 2 B). Paratypes (KLK, 5: 16–23 m, Isla Maria Cleofa, Islas Tres Marias, Mexico, 21.300°N, 106.276°W. One figured: Fig. 3 C).

Unfigured paratypes, all from 16–23 m, Isla Maria Cleofa, Islas Tres Marias, Mexico, 21.300°N, 106.276°W, ex KLK: ( AMNH 314981, 2), ( USNM 1081938, 3), ( ZMA Moll. 4.05.0 19, 2).

Type Locality. 30–35 m, Baja Alcyone, Isla del Coco, Costa Rica, 5.533°N, 86.983°W.

Etymology. The name honors the discoverer of the species and longtime student of the Panamic micromolluscan fauna, Kirstie Kaiser, Puerto Vallarta, Mexico.

Description. Shell small (0.4–0.6 mm), trochiform depressed, off­white. Protoconch of one whorl, with fine axial sculpture from apicalmost portion to periphery, adapical surface smooth, no apertural varix, apertural margin sinusoid. Teleoconch I of 0.825 whorls, 17 – 20 distinct axial cords, interstices filled with fine irregular growth marks, no spiral sculpture. Teleoconch II of 0.333 – 0.4 whorls. Shoulder flat, axial cords of same spacing as on teleoconch I, interstices filled with fine irregular growth lines, no spiral sculpture, suture distinct. Base with distinct constriction below selenizone, same sculpture as on shoulder. Umbilicus open, moderately wide, bordered by strong spiral cord, walls straight, with axial growth marks, underside of protoconch visible through umbilicus. Selenizone above periphery, at 45° angle to coiling axis, keels moderately strong, moderately elevated, growth marks distinct; slit open, with parallel margins. Aperture subquadratic, roof overhanging. Operculum round, thin, covering aperture, multispiral with central nucleus.

Radula ( Fig. 4 ) rhipidoglossate. Rachidian triangular, cusp with seven denticles, central one largest, arranged in V. Lateral teeth 1–3 similar, three denticles on outer margin of cusp. Lateral tooth 4 reduced, with two points on cusp. Lateral tooth 5 broadened enlarged, with approximately six denticles on inner margin of cusp. Radular interlock of central field moderate. Inner marginal teeth spoon­shaped, with one to two denticles on inner margin, six to seven denticles on outer margin; outer marginal teeth spoon­shaped, with many fine denticles on each side of cusp.

Differential diagnosis. The species shows little intraspecific variation, both within population as well as between populations. Figure 2 shows three specimens from the same population, and Figure 3 shows three specimens from three distinct islands. Sinezona rimuloides (Carpenter, 1865) from the Panamic and Southern and Central California, has a more elevated spire, strong axial sculpture on the protoconch, and closes the slit to a foramen.

Scissurella lobini (Burnay & Rolán, 1990) from the Caribbean has a similar overall shape, but has fewer axials (13 vs. 17–20 on teleoconch I), and has a protoconch with strong axial sculpture.

Scissurella maraisorum new species from South Africa has a similar overall shape, but has somewhat fewer axials (14–18 vs. 17–20 on teleoconch I) and on the shoulder of teleococh II the axials are becoming indistinct, while they remain well­developed on the base.

Distribution. Pacific coast of Panamic Province and its offshore islands from 4°N to 28.5°N.

Specimen records. Colombia, Isla de Malpelo. 38 m, 4.002°N, 81.611°W (KLK, 1). 26–50 m, Hammerwall, 4.007°N, 81.604°W (KLK, 3). 13–30 m, North Rock, Little Bob Islet, 4.003°N, 81.602°W (KLK, 1). 33–62 m, Tiger Mount, 4.007°N, 81.602°W (KLK, 1). 10–43 m, NE Coral Gardens, 4.987°N, 81.604°W (KLK, 2).

Costa Rica, Isla del Coco. 10–16 m, Punta Rodrigues, 5.510°N, 87.090°W (KLK, 8). 26–35 m, SSW Punta Rodrigues, 5.510°N, 87.090°W (KLK, 17). 20–33 m, North Islet, Islas dos Amigos, 5.515°N, 87.102°W (KLK, 9). Baja Alcyone, 5.533°N, 86.983°W (SBMNH 348769, 16). 23–30 m, Sharkfin Rock, SSW Punta Rodriguez, 5.533°N, 86.983°W (KLK, 8). 10–13 m, Bahía Westion, Isla Pajara, 5.547°N (KLK, 2).

Costa Rica. 9–13 m, N side Isla del Caño, Puntarenas, 8.721°N, 83.885°E (LACM 72– 63, 1). 13–17 m, Guanacaste, Punta Santa Elena, Costa Rica, 10.893°N, 85.964°W (LACM 72–30).

France, Clipperton Island. 12–15 m, 10.305°N, 109.198°W (KLK, 3).

Mexico. Islas Revillagigedo, Isla Socorro, 19.300°N, 111.650°W (SBMNH). 15–19 m, Cabo Middleton, Isla Socorro, Islas Revillagigedo, 18.780°N, 110.990°W (KLK, 2). 12–18 m, E side Lava Bay, Isla San Benedicto, Islas Revillagigedo, 19.300°N, 110.790°W (KLK, 50). 16–23 m, Isla Maria Cleofa, Islas Tres Marias, 21.300°N, 106.276°W (KLK, 20). 8–11 m, Roca Blanca, Isla San Juanito, Islas Tres Marias, 21.738°N, 106.700°W (KLK, 3). 13–30 m, SW side Guadalupe Island ( Isla Afeura, Adentro, 5 fm bank, & basalt arches), Baja California, 28.900°N, 118.292°W (LACM 72–120, 1). 10–25 m, Isla San Pedro Nolasco, Sonora, 70.600°N, 111.367°W (LACM 67–4). Baja California, Bahía de Los Angeles (28.917°N, 113.500°W), 15 fms, May 1975 (LACM 75–9). 3–17 m, Baja California Sur, Bahía Magdalena, 24.540°N, 112.067°W (LACM 71–14). 10–17 m, Baja California Sur, Isla Ceralvo, 24.167°N, 109.867°W (LACM 71–24). 18–37 m, Baja California Sur, Rancho Palmilla, 22.967°N, 109.800°W (LACM 66–17). 18–37 m, Baja California Sur, Punta Gorda, 23.133°N, 109.583°W (LACM 66–18). 5–10 m, Jalisco, Islas Marietas, 20.750°N, 105.500°W (LACM 65–14).

Panama. 10–21 m, Roca Próspera Islet, Golfo de Chiriquí, Coiba National Park, 7.776°N, 81.759°W (KLK, 20). 0 m, Canal Zone, Farfan Beach, 8.933°N, 79.567°W (LACM 75–56).

Figures

FIGURE 1. Holotype of Scissurella kaiserae new species Baja Alcyone, Isla del Coco, Costa Rica (SBMNH 348769). Scale bar shell = 500 µm. Scale bar protoconch = 100 µm.

FIGURE 2. Paratypes of Scissurella kaiserae new species Baja Alcyone, Isla del Coco, Costa Rica (SBMNH 359438). Scale bars shell = 250 µm. Scale bars protoconch = 100 µm.

FIGURE 3. Paratypes of Scissurella kaiserae new species A. 10 – 21 m, Roca Próspera Islet, Golfo de Chiriqui Coiba National Park, Panama, 7.776 ° N, 81.759 ° W (KLK). B. 12 – 18 m, E side Lava Bay, Isla San Benedicto, Islas Revillagigedo, Mexico, 19.300 ° N, 110.790 ° W (KLK). C. 16 – 23 m, Isla Maria Cleofa, Islas Tres Marias, Mexico, 21.300 ° N, 106.276 ° W (KLK). Scale bar shells = 500 µm. Scale bars protoconch = 100 µm.

FIGURE 4. Scissurella kaiserae new species. 16 – 23 m, Isla Maria Cleofa, Islas Tres Marias, Mexico, 21.300 ° N, 106.276 ° W (KLK). A. Entire radula. Scale bar = 100 µm. B. Section of radula enlarged. Scale bar = 10 µm. C. Operculum. Scale bar = 100 µm.