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Thierry VULLIETExpert- Messages : 4790
Date d'inscription : 28/02/2010
Age : 65
Localisation : Australie 
Americoliva grovesi (Petuch & Myers, 2014)
Sam 17 Mai 2014 - 10:45
Oliva (Americoliva) grovesi - Petuch, E.J. & R.F. Myers, 2014
Description: Shell of average size for genus, extremely narrow and elongated, fusiform, with straight sides and high, elevated spire; shoulder almost non-existent, grading directly into spire whorls; filament channel narrow and deep, bounded by sharp, raised carina; fasciole and fascicular band poorly-developed, proportionally narrow, confined to anterior one-fourth of body whorl; spire whorls protracted, approximately one-fourth length of body whorl, partially covered with thick callus; columella edged with 16-17 thin, evenly-spaced teeth, with teeth becoming larger and better-developed toward anterior end; posterior one-fifth of columella smooth, without teeth; body whorl pale cream-yellow overlaid with open network of interconnected large, pale orange elongated triangles and zig-zag flammules; edge of filament channel marked with widely-spaced large, elongated orange triangular flammules; fasciole and fascicular band cream-white, marked with scattered faint orange flammules; aperture proportionally narrow, widening slightly toward anterior end; columella and interior of aperture pale cream-white; protoconch proportionally very large, rounded, dome-like, composed of 2 whorls, pale cream in color.
Type Specimens: Holotype: length 44 mm, width 15 mm, LACM 3268; Paratype: length 41 mm, width 15 mm, USNM 1155470, collected by diver from 30-40 m depth, in sand, off Santa Catalina Island, Baja California del Sur, Gulf of California, Mexico (25 degrees 30.2 minutes N, 110 degrees 46.3 minutes W; in the collection of the Division of Mollusks, National Museum of Natural History, Smithsonian Institution, Washington, D.C.
Type Locality: Dredged from 128 m depth on the Outer Gorda Bank, 6.5 miles from Punta Gorda, Baja California del Sur, Gulf of California, Mexico (23 degrees 01.56 minutes N, 109 degrees 28.5 minutes W). The holotype was collected by the R/V Velero IV (AHF 1729-49), 12 March 1949.
Range: The new species appears to be endemic to the deep banks and seamounts off the southern tip of Baja California del Sur, Mexico, in an area extending from the Outer Gorda Bank to Santa Catalina Island.
Etymology: Named for Lindsey T. Groves, Collections Manager of the Department of Malacology, Los Angeles County Museum of Natural History, in recognition of his many contributions to the systematics and taxonomy of living and fossil gastropods.
Discussion: With its extremely elongated shape, straight sides, and high, protracted spire, Americoliva grovesi stands out as very different from all the other known Panamic Province Americoliva species (see Petuch, 2013: 209-210 for a discussion and list of all 14 known Panamic taxa). The only other olive that comes even close, morphologically, to this new Gulf of California species is Americoliva deynzerae (Petuch and Sargent, 1986), an elongated shell that is endemic to Cocos Island, Costa Rica (Petuch and Sargent, 1986: 149-150, plate 28, figures 12 and 13). Americoliva grovesi differs from its Cocos Island congener in being an even more slender and fusiform shell with a proportionally higher spire, in having a fainter and more diffuse color pattern, in having a distinctive cream-white base color, and, most importantly, in having a proportionally much larger and more prominent dome-shaped protoconch. The two type specimens of A. grovesi, although having the same exact shell shape, proportions, and protoconch structure, differ somewhat in the intensity of the color pattern, with the Smithsonian paratype being darker than the cream-colored holotype. This spectrum of variability is typical of the genus Americoliva, where all 14 known Panamic species are known to range in color from white and golden forms to melanistic varieties, often occurring within the same population. With the holotype coming from 128 m depth, A. grovesi is also the deepest-dwelling olive shell known from the Gulf of California region. Further collecting on, and exploration of, the seamounts and deep banks at the mouth of the Gulf of California may show that this unusual new species has a wider distribution than is shown here.
Description: Shell of average size for genus, extremely narrow and elongated, fusiform, with straight sides and high, elevated spire; shoulder almost non-existent, grading directly into spire whorls; filament channel narrow and deep, bounded by sharp, raised carina; fasciole and fascicular band poorly-developed, proportionally narrow, confined to anterior one-fourth of body whorl; spire whorls protracted, approximately one-fourth length of body whorl, partially covered with thick callus; columella edged with 16-17 thin, evenly-spaced teeth, with teeth becoming larger and better-developed toward anterior end; posterior one-fifth of columella smooth, without teeth; body whorl pale cream-yellow overlaid with open network of interconnected large, pale orange elongated triangles and zig-zag flammules; edge of filament channel marked with widely-spaced large, elongated orange triangular flammules; fasciole and fascicular band cream-white, marked with scattered faint orange flammules; aperture proportionally narrow, widening slightly toward anterior end; columella and interior of aperture pale cream-white; protoconch proportionally very large, rounded, dome-like, composed of 2 whorls, pale cream in color.
Type Specimens: Holotype: length 44 mm, width 15 mm, LACM 3268; Paratype: length 41 mm, width 15 mm, USNM 1155470, collected by diver from 30-40 m depth, in sand, off Santa Catalina Island, Baja California del Sur, Gulf of California, Mexico (25 degrees 30.2 minutes N, 110 degrees 46.3 minutes W; in the collection of the Division of Mollusks, National Museum of Natural History, Smithsonian Institution, Washington, D.C.
Type Locality: Dredged from 128 m depth on the Outer Gorda Bank, 6.5 miles from Punta Gorda, Baja California del Sur, Gulf of California, Mexico (23 degrees 01.56 minutes N, 109 degrees 28.5 minutes W). The holotype was collected by the R/V Velero IV (AHF 1729-49), 12 March 1949.
Range: The new species appears to be endemic to the deep banks and seamounts off the southern tip of Baja California del Sur, Mexico, in an area extending from the Outer Gorda Bank to Santa Catalina Island.
Etymology: Named for Lindsey T. Groves, Collections Manager of the Department of Malacology, Los Angeles County Museum of Natural History, in recognition of his many contributions to the systematics and taxonomy of living and fossil gastropods.
Discussion: With its extremely elongated shape, straight sides, and high, protracted spire, Americoliva grovesi stands out as very different from all the other known Panamic Province Americoliva species (see Petuch, 2013: 209-210 for a discussion and list of all 14 known Panamic taxa). The only other olive that comes even close, morphologically, to this new Gulf of California species is Americoliva deynzerae (Petuch and Sargent, 1986), an elongated shell that is endemic to Cocos Island, Costa Rica (Petuch and Sargent, 1986: 149-150, plate 28, figures 12 and 13). Americoliva grovesi differs from its Cocos Island congener in being an even more slender and fusiform shell with a proportionally higher spire, in having a fainter and more diffuse color pattern, in having a distinctive cream-white base color, and, most importantly, in having a proportionally much larger and more prominent dome-shaped protoconch. The two type specimens of A. grovesi, although having the same exact shell shape, proportions, and protoconch structure, differ somewhat in the intensity of the color pattern, with the Smithsonian paratype being darker than the cream-colored holotype. This spectrum of variability is typical of the genus Americoliva, where all 14 known Panamic species are known to range in color from white and golden forms to melanistic varieties, often occurring within the same population. With the holotype coming from 128 m depth, A. grovesi is also the deepest-dwelling olive shell known from the Gulf of California region. Further collecting on, and exploration of, the seamounts and deep banks at the mouth of the Gulf of California may show that this unusual new species has a wider distribution than is shown here.
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