Coronium petalos, Houart, Roland & Sellanes, Javier, 2010

Houart, Roland & Sellanes, Javier, 2010, Description of a new Coronium s. l. (Gastropoda: Muricidae: Trophoninae) from south-central Chile and a brief survey of the genus Coronium Simone, 1996, Zootaxa 2346, pp. 62-68 : 63-67

? Coronium petalos new species

( Figs 1–7, 17, 20–21 , 24–27, 29 )

Type material. Holotype 64.4 x 31.2 mm, MNHNCL- 6746 (lv); paratype 45.9 x 20.8 mm, MNHNCL-6747 (dd).

Type locality. Chile, 37°56.79' S, 74°01.25' W, living at 608 m, October 5, 2007, Cruise VG-07, RV “Vidal Gormáz”, Stn AGT-17, coll JS.

Description of the holotype. Shell large and broad for the genus, 64.4 mm height x 31.2 mm width, broadly-ovate, weakly spinose, lightly built. Subsutural ramp weakly sloping, weakly convex. Shell greyishwhite with light tan tinge on subsutural ramp and siphonal canal. Aperture glossy white within. Spire high. Protoconch unknown (eroded). Teleoconch of five broad, convex, strongly shouldered preserved whorls. Other whorls eroded. Suture impressed. Axial sculpture of last teleoconch whorl consisting of 18 low, narrow, lamellose ribs, each with short, narrow, open spine at shoulder. Occasionally with other very short spines where axial ribs cross primary spiral cords. Penultimate whorl with 14 or 15 axial ribs of which some are eroded. Axial sculpture of early whorls completely eroded. Spiral sculpture of last teleoconch whorl of moderately high, narrow, squamous, primary and secondary cords: P1, s1, t1, P2, P3, s3, P4, P5, s5, P6, s6, followed by 13 or 14 lower cords on siphonal canal. Penultimate whorl with visible P1, s1, P2, P3. Spiral sculpture of other whorls eroded. Aperture broad, roundly-ovate. Columellar lip narrow, smooth, with a small, weak knob abapically. Rim completely adherent. Anal notch shallow, broad. Outer lip partly broken, smooth within. Siphonal canal broken at tip, long, 44 % of total shell length, straight, broadly open.

Operculum ( Figs. 20–21 ) dark brown, ovate with apical nucleus in center and numerous concentric ridges. Attached surface with five or six growth lines and broad callused rim.

Radula ( Figs. 24–27 ) rachiglossate with a rachidian tooth bearing a long, narrow, central cusp, a narrow, short, lateral denticle on the inner side of the shorter lateral cusp and several outer lateral denticles between the lateral and the low, fairly broad, marginal cusps. Central cusp longest. Lateral cusps splayed outwards. Lateral teeth sickle-shaped with long, narrow cusp and broad base.

Preserved animal ( Fig. 29 ) is pale yellowish in color, tentacles are mid sized with sub-terminal black eyes of moderate size. The penis is broad and muscular, extends half the length of the mantle cavity and has a terminal papilla.

Remarks. The generic classification of? Coronium petalos n. sp. is based on shell, operculum and radula characters. The shell is most similar to C. wilhelmense , a species also described from Chile. The radula ( Figs. 24–27 ) is similar to that of Coronium , having a rachidian tooth with a narrow, long, central cusp, a short, narrow, lateral denticle fused at base of the inner side of the lateral cusp, and shorter lateral cusps with outer lateral denticle and several outer lateral denticles between it and the marginal cusp as illustrated in Fig. 28 , in Pastorino (2005: 68 & 74, figs. 77–78, 75, 118–119), in Pastorino et al. (2007: 63, figs. H–K) and in Pastorino & Penchaszadeh (2009: fig. 3). There are no significant differences observed in these illustrated radulae beyond those seen in other muricid genera, such as the number of outer lateral denticles between the lateral cusp and the marginal cusp, or/and minor differences in the length or width of the denticles. The operculum ( Figs. 20–21 ), with an apical nucleus, resembles the operculum of Coronium , although it is ovate rather than triangular as in typical Coronium species ( Figs. 22–23 ). Similarly, Trophon s.s. has a broadly ovate operculum with a lateral nucleus on the lower right, as in ocenebrine species ( Ocenebra , Nucella , etc.). Opercula from Coronium were illustrated by Simone (1996: 47, fig. 3; 50, fig. 13), by Pastorino (2005: 68, fig. 74) and Pastorino et al. (2007: 63, figs C and G).

? Coronium petalos n. sp. differs from C. wilhelmense and from C. cf. C. wilhelmense from Uruguay ( Figs. 8–11 , 18, 22–23 ) in having a broader and larger shell relative to the number of teleoconch whorls, a relatively shorter siphonal canal, a more strongly sloping subsutural ramp, more numerous and more lamellate axial ribs with comparatively shorter shoulder spinelets, and more regular, well defined spiral cords, while narrower, more dense, lower and irregular in C. wilhelmense . Coronium coronatum ( Figs. 12–16 , 19 , 28 ) differs in having a smaller, narrower shell with broader, more rounded and fewer axial ribs and a less strongly sloping subsutural ramp.

Other species of trophonines living off Chile are Trophon geversianus ( Pallas, 1774) and T. plicatus ( Lightfoot, 1786) ( Pastorino, 2005) , while other recently described species were included in Trophon by McLean & Andrade (1982) and in Trophon s.l. by Houart (2003) and Houart & Sellanes (2006). Although trophonines are notoriously variable in shell morphology, none of these species is close to the new species described here, which is distinguished altogether by its strong spiral sculpture, broad teleoconch whorls, high spire and long siphonal canal.

Etymology. Petalos , meaning broad in Greek.

Figures

FIGURES 17 – 23. 17. Coronium petalos n. sp. (holotype). 18. Coronium cf. C. wilhelmense (Ramírez-Bohme, 1981), off Uruguay, crab traps, 300 – 500 m, 27.3 mm, coll. RH. 19. Coronium coronatum (Penna-Neme and Leme, 1978), Southeast Brazil, 21 ° 32 ' S, 40 ° 09 ' W, 295 – 300 m, 26.7 mm, coll. RH. 20 – 21. Operculum of Coronium petalos n. sp. (holotype). Scale bar 2 mm. 22 – 23. Operculum of Coronium cf. C. wilhelmense (Ramírez-Bohme, 1981), Uruguay, 36 ° 30 ' S, 53 ° 41 W, 280 – 300 m, coll. RH

FIGURES 24 – 29. 24 – 27. Radula of Coronium petalos n. sp. (holotype). 28. Radula of Coronium coronatum (Penna- Neme and Leme, 1978), Brazil (MNHN). 29. Animal of Coronium petalos n. sp. (holotype). Scale bars: 24: 100 µm; 25 - 27: 10 µm; 28: 20 µm.

FIGURES 2 – 16. 2 – 7. Coronium petalos n. sp. 2 – 4. Chile, 37 ° 56.79 ' S, 74 ° 01.25 ' W, 608 m, 64.4 mm, holotype MNHNCL- 6746. 5 – 7. Same locality, 45.8 mm, paratype MNHNCL- 6747. 8 – 11. Coronium cf. C. wilhelmense (Ramírez- Bohme, 1981). 8 – 10. Uruguay, 36 ° 30 ' S, 53 ° 41 W, 280 – 300 m, 35 mm, coll. RH. 11. Off Uruguay, crab traps, 300 – 500 m, 27.3 mm, coll. RH. 12 – 16. Coronium coronatum (Penna-Neme and Leme, 1978). 12 – 14. Southeast Brazil, 21 ° 32 ' S, 40 ° 09 ' W, 295 – 300 m, 26.7 mm, coll. RH. 15 – 16. Brazil, Rio de Janeiro State, off Cabo de São Tomé, 22 ° 34 ’ S, 40 ° 29 ’ W, 213 m, sta. ix., holotype MZUSP 18994. Photo courtesy L. R. L. Simone.