Benthofascis conorbioides, Tucker & Tenorio & Stahlschmidt, 2011

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 : 9-10

Benthofascis conorbioides new species

Figures 3 , A–D

Type material. Holotype in MNHN 23068 (38.6 mm long, 15.1 mm wide); Paratypes: SBMNH 424097 , 1 specimen from the type locality; Peter Stahlschmidt collection, 1 specimen trawled by prawn trawlers, on sand and rubble, off Bundaberg, central coast of Queensland, Australia .

Type locality. 80–120 m, off Mooloolaba , southern Queensland, Australia .

Range. Known only from Queensland, Australia.

Description. Shell is moderate in size. The three specimens of the type series averaged 43.3 mm long (range = 38.6–49.6 mm). The mean shell width was 16.3 mm (range = 15.1–17.0 mm). It is solid and ovate-fusiform. Color pattern consists of flesh colored bands over white. Two narrow colored bands are present on the teleoconch with one at the shoulder and one near midbody. The anterior end is shaded slightly. Sutural ramp of the spire is also banded with this flesh color. The larger specimen has 6.5 whorls including the protoconch. Sculpture on the protoconch consists of fine spiral grooves. There are 4 or 5 spirals on the sutural ramps of the early teleoconch whorls. The axials are not developed but growth lines cross the spaces between adjacent spirals. On the sutural ramps of outer teleoconch whorls the number of spirals is reduced to 2 to 4. Growth lines cross the interspaces between adjacent spirals. The body is ornamented by deep, pronounced spiral grooves separated by interspaces of varying width. On the posterior half of the shell these interspaces are slightly wider than they are on the anterior half of the body whorl. The sides of the body whorl are convex and the shoulder angle is exceedingly indistinct. The aperture is narrow with a deep sinus, the lip is thin, straight and is produced medially. Inner shell walls are resorbed ( Fig. 3C ). The columella is nearly straight. There is a groove near its posterior end just where the columella meets the body whorl. There is a denticle inside this groove. The anal sinus is not symmetrical and is deepest at the suture. The protoconch is paucispiral, blunt and swollen looking. The operculum and radula were not observed.

Discussion. This species with its deep widely spiral grooves and interspaces of variable width looks nothing like the other species of Benthofascis included here. It more closely resembles two fossil species from the Miocene ( Fig. 3E ) and Oligocene ( Fig. 3F ) of Australia. These were both placed in Conorbis by various authors ( Tucker 2004 for a review; Tucker & Tenorio 2009). The species are Benthofascis atractoides ( Tate 1890) new combination ( Fig. 3E ) and B. otwayensis ( Long 1981) new combination ( Fig. 3F ). The latter species from the Oligocene of Victoria was originally described as a subspecies of the former, a Miocene species from South Australia. Of these two species, the Miocene B. atractoides is closest to B. conorbioides . The Oligocene species, B. otwayensis is wider bodied (holotype shell width/shell length = 0.47) than is B. atractoides (holotype shell width/shell length = 0.40) or B. conorbioides (type series: shell width/shell length mean = 0.39 (range = 0.34–0.40). Recognition of these Australian fossils as members of Benthofascis extends the geologic history of the genus to the Oligocene.

Although superficially similar, Benthofascis conorbioides and B. atractoides differ in the length of the aperture compared to the length of the shell. B. conorbioides has a much longer aperture than does B. atractoides . The aperture of B. conorbioides ranges from 57% to 62% (mean = 59%, n = 3) of the length of the shell. In contrast the aperture of the holotype of B. atractoides is 55% of the length of the shell. This can be confirmed by finding the point on the body whorl where the suture of the last whorl with the body whorl is located. This point is located well anterior to the shoulder in B. atractoides ( Fig. 3E ). In B. conorbioides the point where the suture of the last whorl meets the body whorl is almost at the shoulder slope ( Fig. 3A ). This may seem a small difference but it results in a lowered degree of scalariformity, which is also an important trait in distinguishing Eocene and Recent cone shells ( Kohn 1990).

This species resembles certain species of Bathytoma such as Bathytoma atractoides ( Watson 1881) . Both have rounded convex sides and bodies ornamented by ridges and sulci. Both also have similar color patterns. However, Benthofascis conorbioides cannot be a Bathytoma because Benthofascis conorbioides has the inner whorls resorbed ( Fig. 3C ). In contrast Bathytoma atractoides does not ( Tucker & Tenorio 2009, Fig. 17F). Protoconchs also differ markedly. The protoconch of Bathytoma species is smooth and has a narrow point ( Powell 1966). In contrast the protoconchs of B. conorbioides and other Benthofascis species are blunt and ornamented with spirals. The anal sinus of Bathytoma species is also more u-shaped because its deepest point is near the center of the subsutural ramp. The anal sinus of B. conorbioides and other Benthofascis species is deepest near the shoulder.

Etymology. The name is suggested by the superficial similarity between Benthofascis conorbioides and species of the extinct genus Conorbis .

Figures

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.