Radiolucina jessicae Garfinkle

Garfinkle, Elizabeth A. R., 2012, A review of North American Recent Radiolucina (Bivalvia, Lucinidae) with the description of a new species, ZooKeys 205, pp. 19-31 : 22-23

Radiolucina jessicae Garfinkle sp. n. Figure 3, 5c

Radiolucina cf. cancellaris Coan and Valentich-Scott, 2012: 360

Diagnosis.

Subovate, extended anteriorly and posteriorly, slightly inflated; with about 11 primary radial ribs, excluding intercalary ribs; commarginal ribs continuing through interspaces creating a rectangular pattern; posterior end with fine commarginal striae and spines of varying heights protruding from shell; pallial line discontinuous, broken into a series of short and long sections with one large segment directed ventrally.

Shell shape.

Subovate, long, extended anteriorly and posteriorly, length longer than height; slightly inflated; maximum length: 6.0 mm, maximum height: 5.3 mm; beaks pointed, prosogyrate.

Sculpture and color.

Average 13 (9-16 n=20) radial ribs, occasional bifurcate usually on larger specimens; commarginal ribs continuing through interspaces, with 6-10 thick intercalary ribs extending to ventral edge of valve, present in most specimens, more pronounced in larger specimens; interspaces shallow and thin towards beak, progressively widening ventrally; anterior side smooth with fine commarginal striae; posterior side also smooth with fine commarginal striae, with a series of average nine (4-15 n=20) thick spines of varying heights protruding from shell; exterior color tan to white, also with brown along ribs; interior color tan, white to cream, shiny; inner shell margin crenulations thin, closely spaced.

Hinge.

Hinge plate thin, slightly curved on either side of cardinal teeth; right valve posterior and anterior cardinal teeth about equal in size, left valve middle tooth wide; lateral teeth large, posterior vertical and anterior horizontal; ligament long, sunken above cardinal teeth.

Adductor muscle and pallial scars.

Pallial line discontinuous, broken into series of large, small segments, with one large segment directed ventrally; anterior adductor scar is large, narrow, diverging from pallial line for about half its length; posterior adductor scar small, wide, pallial line joins anteriorly to most ventral point.

Anatomy from rehydrated dried specimens.

Inhalant aperture usually smaller than exhalant, elongate, often narrow; tissue bridge between apertures usually narrow; ventral mantle fusion thin, narrow; mantle fusion variable, usually not fused below anterior adductor muscle; rectum curves dorsally around posterior adductor muscle and ends at exhalant aperture.

Type locality and type specimens.

North America, Mexico, Baja California Sur, Bahía Concepción, Bahía Coyote; 26°43'50"N, 111°53'30"W; 12 m.

Holotype.

SBMNH 353469, length: 4.5 mm. Paratypes. SBMNH 149936, 6 unpaired valves; LACM 3231, 4 unpaired valves; NHMUK 20120066, 2 unpaired valves; USNM 1179317, 2 unpaired valves.

Distribution.

East Pacific, W side of Isla El Muerto, Baja California, Mexico (30°4.00'N, 114°33.00'W) to Bahía Concepción, Baja California Sur, Mexico (26°39.00'N, 111°48.00'N). Also known from Sonora, Guaymas, Bahía San Carlos, Sonora, Mexico (27°56.1.00'N, 111°5.00'W) to San Carlos, Gulf of Panama (8°29.00'N, 79°56.00'W). Usually collected among gravel and shells; known from 13-27 m deep.

Etymology.

Named in honor of Jessica Sanford from Santa Barbara, California for being an inspiring scientist, meaningful mentor, and wonderful friend.

Comparisons.

See comparisons of Radiolucina amianta , Radiolucina cancellaris ,and Radiolucina jessicae in Table 1.

Radiolucina waccamawensis (Dall 1903), from the Pliocene of the Waccamaw district, South Carolina, has about 10 strong radial ribs with deep interspaces, compared to Radiolucina jessicae which has about 13 radial ribs with shallow interspaces, and about eight intercalary ribs. The morphologic characters of Radiolucina waccamawensis are closer to Radiolucina cancellaris .

Discussion.

Different morphologic characters among different ages of Radiolucina cancellaris are common, specifically ontogenetic changes in shape, rib number, and hinge teeth. Further research and use of additional characters, specifically DNA studies, ( Taylor et al. 2011) could present more details and explanation for the variable characters observed, and could possibly reveal more new species within the Radiolucina cancellaris complex.