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

Benthofascis biconica ( Hedley, 1903)

Figures 1 , A–F; 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 , dredged, 20 July 1972, Station: SBS 2; AMS C.468237, 2 specimens from 9 m, Twofold Bay , New South Wales, 37º5'S, 149º55'E ; AMS C.388783, 2 specimens from 66 m, off North Head, Sydney , New South Wales, 33º49.5'S, 151º18.1'E ; 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) ; AMS C.468233, 1 specimen from 77 m, 5 km E of Long Bay, Sydney , New South Wales, 33º58.150'S, 151º18.020'E , 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 ). 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 ). 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 ). The tooth has a slight but distinct waist.

Discussion. Hedley (1903) aptly described the holotype of this species ( Figs. 1A–C ). 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 , & F), whereas those of B. pseudobiconica are not ( Figs. 2E, G , & 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 ) and B. lozoueti ( Figs. 3I, K , & L). The latter species has a nearly smooth protoconch with more than 2 whorls ( Fig. 3J ), 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 ). 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 , & D) and the two fossil species ( Figs. 3E & F ) 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 , & L) and B. angularis ( Figs. 2A & C ) 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.

Figures

FIGURE 1. A–C. Holotype of Benthofascis biconica (AMS C.016448, 35–37 m deep, Shoalhaven Bight, New South Wales, Australia), height 18 mm, width 8 mm, ventral (A) and side (B) views with enlargement of spire (C). D–E. Benthofascis biconica (AMS C.468235, 5.7 km E of Mistral Point, Sydney, New South Wales, 33º56.470'S, 151º19.630'E, 71–77 m deep), heigth 29.8 mm, width 10.7 mm, ventral view (D) and x-ray (E). F. Benthofascis biconica (AMS C.468235, same locality data as above), height 17.9 mm, width 7.7 mm. G–H. Holotype of Benthofascis sarcinula (AMS C.19871, 203 m deep, 20 km miles E of Cape Byron, New South Wales, Australia), height 7 mm, width 4 mm, ventral view (G) and an enlargement of the spire (H). I–K. Benthofascis sarcinula (USNM 902892, SSE of Lakes Entrance, Gippsland Lakes, Victoria, Australia), height 16.6 mm, width 7.4 mm, ventral (I) and lateral views (J) with an enlargement of the spire (K). L–N. Benthofascis sarcinula (USNM 902893, Victoria, Australia), height 24.6 mm, width 10.7 mm, ventral (L) and lateral (M) views and an x-ray (N). Scale bars represent 1 mm.

FIGURE 2. A–D. Holotype of Benthofascis angularis new species (MNHN 23067, 30 m deep, off Cape le Grande, Esperance, southwest Western Australia), height 27 mm, width 11.1 mm, ventral (A) and lateral (B) views with enlargement of spire (C) and an x-ray (D). E, F. Holotype of Benthofascis pseudobiconica new species (MNHN 23069, off Cape Moreton, Queensland, Australia), height 39.8mm, width 12.8 mm, ventral (E) and lateral (F) views. G.Paratype of Benthofascis pseudobiconica new species (ANSP 424978, 183 m deep, off Cape Moreton, S. Queensland, Australia), height 35.3 mm, width 11.8 mm, ventral view. H–K. Paratype of Benthofascis pseudobiconica new species (USNM 902891, South Australia, Australia) height 36.4 mm, width 12.4 mm, ventral (H) and lateral (I) views with an enlargement of the spire (J) and an x-ray (K). Scale bars represent 1 mm.

FIGURE 3. A–C. Holotype of Benthofascis conorbioides new species (MNHN 23068, trawled 80–120 m, off Mooloolaba, S. Queensland, Australia), height 38.7 mm, width 15.4 mm, ventral view (A), with an enlargement of the spire (B) and an x-ray (C). D. Paratype of Benthofascis conorbioides new species (SBMNH 424097, trawled on sand and rubble, 80–120 m, off Mooloolaba, S. Queensland, Australia) height 41.8 mm, width 17.0 mm, ventral view. E. Holotype of Benthofascis atractoides (SAMA T750A, Kent Town Bore, Clayey greensands, Janjukian?, L. Miocene), height 16.5 mm, width 6.5 mm (reproduced from Long, 1981, Pl. 6, Fig. 14, with permission), ventral view. F. Holotype of Benthofascis otwayensis (NMVM P42959, Point Flinders, Cape Otway, Victoria, Australia. Glen Aire Clay, U. Aldingan, L. Oligocene), height 19.75 mm, width 8.75 mm (reproduced from Long, 1981, Pl. 6, Fig. 15, with permission), ventral view. G. Paratype of Benthofascis lozoueti (NMSA L5679/T1867), South New Caledonia, N/O "Alis" campaign, Stn. DW 721, 22º54'S, 167º17'E, height 16.5 mm, width 7.2 mm, ventral view. H. Benthofascis lozoueti (MNHN IM200742331, 496 m deep, Norfolk Ridge, 22º50'S, 167º16'E), length 16.4 mm, width 7.0 mm, x-ray. I–K. Holotype of Benthofascis lozoueti (MNHN 3053, 530 m deep, Norfolk Ridge, 22º58'S, 167º20'E), height 21.5 mm, width 15 mm, ventral (I) and lateral (J) views with an enlargement of the spire (K). L. Paratype of Benthofascis lozoueti (AMS C.415308), 525–574 m deep, New Caledonia, 22º54'S, 167º17'E, height 17.5 mm, width 8.0 mm, ventral view. Scale bars represent 1 mm.

FIGURE 4. A, B. Radular teeth extracted from Benthofascis biconica (AMS C.468232, shell length of 15.5 mm), photomicrograph (A) and drawing (B) showing internal structures. C, D. Radular teeth extracted from Benthofascis biconica (AMS C.468234, shell length of 15.2 mm), photomicrograph (C) and drawing (D) showing internal structures. E, F. Radular teeth extracted from Benthofascis pseudobiconica (AMS C.373099, shell length of 17.3 mm), photomicrograph (E) and drawing (F) showing internal structures. Scale bar represents 0.1 mm for A–F. G. G. Electron micrographic study of the radular tooth of Benthofascis lozoueti Sysoev & Bouchet, 2001, (MNHN IM200742331, 496 m deep, Norfolk Ridge, 22º50'S, 167º16'E, height 16.4 mm, width 7.0 mm, teeth from the same specimen shown in Fig. 3H). Scale bar dimensions are explained in the figure.