Cocculina delphinicula

Zhang, Shuqian & Zhang, Suping, 2018, Cocculina delphinicula sp. nov., a new cocculinid species from whale bone in the East China Sea (Gastropoda: Cocculiniformia), Zootaxa 4455 (1), pp. 189-195: 191-193

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Cocculina delphinicula

sp. nov.

Cocculina delphinicula  sp. nov.

( Figs 2–4View FIGURE 2View FIGURE 3View FIGURE 4)

Type material. Holotype: MBMAbout MBM 285103 (length 4.9 mm, width 3.8 mm), East China Sea, November 2017; Paratypes: MBMAbout MBM 285104, six specimens, collected with the holotype at the type locality, November 2017.

Six additional immature specimens were also observed.

Type locality. East China Sea, approximately 28°N 127°E, at depth of 300–400 m. 

Etymology. The species is named after dolphin family Delphinidae  because it was found living on a dolphin skull.

Diagnosis. Shell medium-sized, depressed, shell width 77%–81% of shell length, height 31%–36% of length. Shell surface sparsely pitted. Protoconch slightly posterior to center, with reticulate sculpture. Teleoconch sculptured with regularly spaced concentric growth lines and even finer radial threads. Aperture oval, longer than wider. Radula has a formula of (ca. 20)+5+1+5+(ca. 20), rachidian vestigial. Lateral 1 weak but well defined. Laterals 2 and 3 similar, overhanging tip with 3–4 cusps. Lateral 4 smaller and slender with a large primary cusp and an outer secondary cusp.

Description. Shell ( Fig. 2 View Figure ; Tab. 1) medium-sized for genus (maximum length 5.9 mm), thin, fragile, white, semi-transparent, periostracum not observed. Shell depressed, height of holotype 0.33 times length. Apex slightly posterior to center, situated at 56–62% of shell length from anterior end. Protoconch offset to left, deflected from longitudinal axis of adult teleoconch by up to 20°. Aperture oval, longer than wide (width/length ratio 0.77–0.81), anterior end slightly narrower than posterior end. Apertural margin not planar, shallowly concave from side to side. Anterior and posterior slopes faintly convex, lateral slopes at first slightly convex, then weakly concave.

Protoconch ( Figs 2E–H View Figure ) about 260 µm long and 145 µm wide, located slightly below the highest point of the shell. Tip of protoconch partly immersed in the posterior slope of the teleoconch. Protoconch surface sculptured with a reticulate pattern of flattened, broad ridges ( Figs 2E–F View Figure ). Surface between ridges of protoconch finely pitted ( Figs 2G–H View Figure ).

Teleoconch sculpture at first with regularly spaced concentric growth lines, then becoming coarser and stronger toward the aperture, crossed by even finer radial threads. The lines and threads producing waved nodules at intersections (see Figs 2C–D View Figure ). Shell surface sparsely pitted (see Fig 2F View Figure ).

Soft parts ( Fig. 3 View Figure ). Copulatory organ bifurcated, at tip of right oral lappet. Foot with rounded pedal sole. Posterior end of foot with a pair of epipodial tentacles. Detailed morphology of head area and dorsal side of animal (visceral mass) could not be observed due to poor preservation.

Radula ( Fig. 4 View Figure ) has a formula of (ca. 20)+5+1+5+(ca. 20). Rachidian vestigial, represented by a longitudinal ridge. Lateral teeth numbering 1–5 in each half row, lateral 1 weak but well defined, having an outline that frequently terminates in a small beaklike cusp. Laterals 2 and 3 similar to each other, with long, parallel-sided shafts, tip overhanging, with 3–4 cusps. Lateral 4 smaller and slender, with a large primary cusp and an outer secondary cusp. Lateral 5 transformed to a broad claw-like tooth, equipped with a large primary cusp and a smaller secondary cusp on either side, finely longitudinally striated on its posterior surface. Marginal teeth with long, laterally compressed shafts, tips overhanging, cutting edges weakly serrated at inner margins and strongly serrated at outer margins.

Remarks. Cocculina delphinicula  sp. nov. is superficially similar to Cocculina alveolata Schepman, 1908  from Indonesia in shell size and sculpture. From that species, however, the new species differs in having a larger width/length ratio (0.77–0.81 vs. 0.72), a less convex anterior slope and a concave rather than elevated apertural margin. Moreover, Cocculina delphinicula  sp. nov. can be separated from Cocculina alveolata Schepman, 1908  by having an outer secondary cusp on the first and fourth lateral teeth.

Five species from Japan, Cocculina japonica Dall, 1907  , Cocculina pacifica Kuroda & Habe, 1949  , Cocculina surugaensis Hasegawa, 1997  , Cocculina tenuitesta Hasegawa, 1997  and Cocculina tosaensis Kuroda & Habe, 1994  as well as two species from Taiwan, Cocculina japonica Dall, 1907  and Cocculina subcompressa Schepman, 1908  ( Wu & Lee 2005; Chen 2005), may represent the geographically closest congeners to Cocculina delphinicula  sp. nov. Of those, Cocculina tenuitesta Hasegawa, 1997  resembles the new species in shell size. However, Cocculina delphinicula  sp. nov. differs from this species in having a depressed shell with regularly spaced, concentric growth lines and finer radial threads, a sparsely pitted shell surface and a protoconch that has wavy ridges and numerous microscopic pits.


San Jose State University, Museum of Birds and Mammals