Benthofascis biconica ( Hedley, 1903 )

Tucker, J. K., Tenorio, M. J. & Stahlschmidt, P., 2011, The genus Benthofascis (Gastropoda: Conoidea): A revision with descriptions of new species, Zootaxa 2796 (1), pp. 1-14 : 3-5

publication ID

https://doi.org/ 10.11646/zootaxa.2796.1.1

DOI

https://doi.org/10.5281/zenodo.5294698

persistent identifier

https://treatment.plazi.org/id/366A374B-F355-FFFA-FF47-F999FE16EB57

treatment provided by

Felipe

scientific name

Benthofascis biconica ( Hedley, 1903 )
status

 

Benthofascis biconica ( Hedley, 1903) View in CoL

Figures 1 View FIGURE 1 , A–F; 4 View FIGURE 4 , A–D

Type material. Holotype is AMS C.016448, shell length 18 mm, shell width 8 mm.

Type locality. 35–37 m, Shoalhaven Bight , New South Wales, Australia

Other specimens. AMS C.468235, 4 specimens from 71–77 m deep, 5.7 km E of Mistral Point, Sydney , New South Wales, 33º56.470'S, 151º19.630'E GoogleMaps , dredged, 20 July 1972, Station: SBS 2; AMS C.468237, 2 specimens from 9 m, Twofold Bay , New South Wales, 37º5'S, 149º55'E GoogleMaps ; AMS C.388783, 2 specimens from 66 m, off North Head, Sydney , New South Wales, 33º49.5'S, 151º18.1'E GoogleMaps ; AMS C.468232, 1 specimen from 71–77 m, 5.7 km E of Mistral Point, Sydney , New South Wales, 33º56.470'S, 151º19.630'E (wet) GoogleMaps ; AMS C.468233, 1 specimen from 77 m, 5 km E of Long Bay, Sydney , New South Wales, 33º58.150'S, 151º18.020'E GoogleMaps , dredged 20 February, 1973, Shelf Benthic Survey.

Range. New South Wales, Australia.

Description. Shell solid, biconical, slightly angled at the shoulder, of more than six whorls. Color apparently flesh-tint. Sculpture: below the shoulder the shell is furrowed by numerous fine spiral grooves, crossed by arcuate growth lines, above the furrows are broader and fewer. Aperture narrow, sinus sutural and deep, outer lip appears to have curved far forward, columella angled in center, spreading broadly and with a small anterior plication. Length, 18 mm; breadth, 8 mm (quoted from Hedley 1903, p. 385–386). Inner shell walls are resorbed ( Fig. 1E View FIGURE 1 ). The operculum is leaf-shaped with a terminal nucleus. It is fairly large and covers most of the apertural opening. The operculum of a specimen (AMS C.468234) with a shell length of 15.2 mm measured 3.25 mm in length. We examined a total of 28 specimens that could be accurately measured. Shell length for these averaged 26.4 mm (range = 10.1– 41.8 mm). Shell width averaged 10.7 mm (range = 4.6–17.6 mm). The radula has a barb and blade at its anterior end ( Figs. 4A–D View FIGURE 4 ). The barb is sharply tipped and this distal tip is curved away from the shaft of the tooth. The barb is about one-third as long as the blade. The distal end of the blade slopes towards the shaft of the tooth and is not much elevated above the shaft of the tooth. There is no anterior fold but there is a C-fold. This fold demonstrates that the tooth is enrolled a minimum of 360 degrees. There are no serrations and no terminating cusp. There is a fold on the shaft of the tooth that begins posterior to the distal end of the blade. This fold extends to the waist of the tooth ( Figs. 4A & C View FIGURE 4 ). The tooth has a slight but distinct waist.

Discussion. Hedley (1903) aptly described the holotype of this species ( Figs. 1A–C View FIGURE 1 ). Laseron (1954) reproduced Hedley's figure and correctly identified the species. However, some subsequent authors have misidentified specimens of Benthofascis pseudobiconica as B. biconica (e.g. Powell 1966; Wilson 1994; Tucker & Tenorio 2009). These two species are similar to each other but differ in shell shape. The shoulders of B. biconica are distinctly angular ( Figs. 1A, D View FIGURE 1 , & F), whereas those of B. pseudobiconica are not ( Figs. 2E, G View FIGURE 2 , & H). The more angular shoulders give B. biconica a stouter appearance compared to the long-bodied B. pseudobiconica .

Two other species have subangular shoulders, namely B. angularis ( Figs. 2A & C View FIGURE 2 ) and B. lozoueti ( Figs. 3I, K View FIGURE 3 , & L). The latter species has a nearly smooth protoconch with more than 2 whorls ( Fig. 3J View FIGURE 3 ), a feature unique among the Benthofascis species. Besides that B. lozoueti is unique among Benthofascis in that the inner shell walls are not remodeled ( Fig. 3H View FIGURE 3 ). We were able to confirm via x-ray that all other species of Benthofascis remodel the inner shell walls. B. angularis does not have the punctate sutural ramps similar to those that B. biconica has.

The body whorl ornamentation of B. conorbioides differs from that of B. biconica . The former species ( Figs. 3A, B View FIGURE 3 , & D) and the two fossil species ( Figs. 3E & F View FIGURE 3 ) have spiral grooves that are widely spaced and that cover the entire body whorl rather than the more closely spaced grooves of B. biconica and B. pseudobiconica . The body whorls of B. lozoueti ( Figs. 3I, K View FIGURE 3 , & L) and B. angularis ( Figs. 2A & C View FIGURE 2 ) are almost smooth.

We illustrate the radulae of two of these species with micrographs and with drawings that show the internal structure of the teeth for the first time. Previous drawings (e.g., Powell, 1966) were misleading as they suggested that the teeth were simple hollow tubes with no internal structure (see Tucker & Tenorio, 2009). Electron micrographs available for B. lozoueti ( Sysoev & Bouchet, 2001) also do not show internal structures. The radulae of B. biconica and B. pseudobiconica that we were able to examine had unexpected structures. There is a definite C-fold and a slight waist both features that were not obvious in previously published drawings of radulae from Benthofascis . This is important because it demonstrates that the tooth is enrolled more than 360 degrees. Moreover a fold is obvious along the shaft of the tooth in all three species. This fold may be homologous to the shaft fold that characterizes the Conilithidae ( Tucker & Tenorio, 2009) . However, this fold is not a shaft fold because it appears that in Benthofascis this fold is an internal one associated with the enrollment of the tooth. The shaft fold of the Conilithidae is an external structure.

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