Coronadoa demisispira , Geiger, Daniel L. & Mclean, James H., 2010

Geiger, Daniel L. & Mclean, James H., 2010, New species and records of Scissurellidae and Anatomidae from the Americas (Mollusca: Gastropoda: Vetigastropoda), Zootaxa 2356, pp. 1-35: 12-15

publication ID 10.5281/zenodo.275645

persistent identifier

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scientific name

Coronadoa demisispira

n. sp.

Coronadoa demisispira  n. sp.

Figure 9View FIGURE 9

Type material. Holotype ( LACM 3113:  Fig. 9View FIGURE 9 C). Paratypes: 26–40 m, Farnsworth Bank, off S side of Catalina Island, California, USA, 33.350 ˚N, 118.517 ˚W ( LACM 3114); 13–30 m, Cortez Bank, 0.5 mile south of Bishop Rock, California, USA, 32.433 ˚N, 119.125 ˚W ( LACM 3115: Fig. 9View FIGURE 9 A –B). All LACM type material leg. J. McLean.

Type locality. 26–40 m, Farnsworth Bank, off S side of Catalina Island , California, USA, 33.350 ˚N, 118.517 ˚W.GoogleMaps 

Additional material examined. 10–23 m, NW side of Guadalupe Island, (Pilot Rock and 5 miles S), Baja California, Mexico, 29.188 ˚N, 118.253 ˚W ( LACM 72 -121, 1). 20–26 m, SW side Natividad Island, Baja California, Mexico, 27.888 ˚N, 115.212 ˚W ( LACM 72 -117, 1). 13–17 m, 5 fathom Bank about 4 miles SW of SE tip of Cedros Island, outer coast Baja California, Mexico, 27.983 ˚N, 115.212 ˚W ( LACM 71 -93, 2). 26 m, San Miguel Island, California, USA, 34.020 ˚N, 120.402 ˚W (DLG 1131, 1). 46 m, off Santa Cruz Island, California, USA, 34.056 ˚N, 119.961 ˚W (DLG 1263, 3).

Etymology. demisi-: Latin for sunken; -spira: Latin for spire. Referring to the flat spire of the species.

Description. Shell small (to 0.75 mm), trochiform depressed. Protoconch of 0.875 whorls, embryonic cap without sculpture, remainder with strong axial ribs, no apertural varix, apertural margin prosocline. Teleoconch of 1.5 whorls, 11–13 raised axial cords, indistinct at suture and towards umbilicus, most pronounced at periphery, interstices with irregular axial growth marks; no spiral sculpture. Umbilicus open, occasionally undersurface of protoconch visible, bordered by knobby carina towards base. Aperture subquadratic D-shaped, lower adumbilical corner pronounced, forming knobby carina of umbilicus. Operculum thin, round, multispiral, nucleus central.

Differential diagnosis. The sympatric C. simonsae Bartsch, 1946  ( Fig. 9View FIGURE 9 A –B and Fig. 10View FIGURE 10 A,C; Fig. 9View FIGURE 9 C and Fig. 10View FIGURE 10 B) is proportionally taller (width to height: simonsae  mean = 1.28, SD = 0.047, n = 4; demisispira  mean = 1.79, SD = 0.22, n = 4; t-test t = - 4.36, p = 0.022). As a corollary, its umbilicus is wider, and tends to have fewer axial cords per unit whorl. The degree of axial sculpturing is variable in both species, from distinct cords to raised lamellae. Coronadoa hasegawai Geiger & Sasaki, 2009  , from temperate Japan is as tall as C. simonsae  .

Remarks. Coronadoa demisispira  is much less common than C. simonsae  ; if the two species are present in the same lot, C. demisispira  comprises at most 10 % of C. simonsae  specimens. This skewed ratio suggests that the two are not dimorphic males and females of the same species. In general, Vetigastropoda  show a male:female ratio of close to 1: 1 (Bretos et al. 1985, Hooker & Creese 1995, Wells & Malay 1995), although there are no data on Scissurellidae  s.l.


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