Thaluta, a new genus of Costellariidae (Mollusca: Gastropoda), with description of a new species

VENUS 62 (3-4): 117-124, 2003

Thaluta, a New Genus of Costellariidae (Mollusca: Gastropoda), with Description of a New Species

Gary Rosenberg and Paul Callomon

Academy of Natural Sciences, 1900 Benjamin Franklin Parkway, Philadelphia, Pennsylvania 19103, USA; rosenberg@acnatsci.org, callomon@acnatsci.org

Abstract: The new genus Thaluta is proposed for a group of small costellariid gastropods from the Indian and Western Pacific Oceans, with Thala maxmarrowi Cernohorsky, 1980 as the type species. A second species from central Japan that was previously misidentified as T maxmarrowi is here described as Thaluta takenoko sp. nov. It differs from the type species in part by having a paucispiral rather than a multispiral protoconch. A series of specimens from Australia with an unknown protoconch may represent a third species of Thaluta. The geographic range of T. maxmarrowi is extended to South Africa. Comparison is made with the genera Thala H. & A. Adams, 1853, Mitromica Berry, 1958 and Zierliana Gray, 1847, with particular reference to Z. anthracina (Reeve, 1844)

Keywords: Thaluta, new genus, Costellariidae, new species, Thaluta takenoko

Introduction

Examination of material from Japan identified in collections and by Turner and Callomon (2001: figs. 14, 15) as Theda maxmarrowi bas revealed a new species which is described herein. This new species appears to be restricted to the Kii Peninsula, and a similar species that is here left unnamed pending discovery of better material occurs in the Torres Strait, Queensland Australia. Thala maxmarrowi was described from Okinawa, later reported from Reunion by Cernohorsky ( 1988) and is here reported from South Africa.

Thala maxmarrowi differs significantly in morphology from the type species of Thala H. & A. Adams, 1853, T. mirifica (Reeve, 1845). With the discovery of a second species closely related to T. maxmarrowi, we name the new genus Thaluta to recognize these differences.

The following acronyms are used: AIM - Auckland Institute and Museum ; AMS - Australian Museum, Sydney, Australia; ANSP - Academy of Natural Sciences, Philadelphia, USA; MNHN -Museum national d 'Histoire naturelle, Paris, France; NMSA - Natal Museum, Pietermaritzburg, South Africa; NSMT - National Science Museum, Tokyo, Japan; UF - Florida Museum of Natural History, University of Florida, Gainesville, Florida, USA.

Systematics

Family Costellariidae MacDonald, 1860

Thaluta n. gen.

Type species: Thata maxmarrowi Cernohorsky, 1980

Description: Shell small, to 10 mm, regularly mit:riform in juveniles but with distinctive lateral expansion of the aperture anteriorly in adults. Protoconch smooth, number of whorls variable.

118 G. Rosenberg & P. Callomon

Teleoconch bears smooth axial ribs, strongest on early whorls, often obsolete or absent on body whorl, with numerous faint, fine spiral cords over part or all of teleoconch. Five to seven strong spiral cords present on lower third of body whorl. Four strong columellar plicae and thickened parietal callus in adult specimens. Siphonal canal short, bounded on left margin by anteriormost columellar fold, siphonal notch present. Apertural lirations present in adults, with leading edges running obliquely to shell axis from about ten degrees behind the labrum posteriorly to the siphonal notch anteriorly.

Discussion: Thaluta resembles Vexillum and Pusia in having lirations in the aperture recessed from the edge of the labrum. In contrast, Thala and Mitromica (see Rosenberg & Salisbury, 2003) Jack lirations but have denticles on the inner edge of the adult lip. Thaluta differs from all other costellariids in that the aperture flares outward anteriorly in the last quarter whorl of growth, making the shell virtually as wide at the level of the third columellar tooth as it is at the periphery of the body whorl. Also, the anteriormost columellar fold is strong and forms the anterior left hand border of the siphonal canal, as seen in some volutids. In other costellariids the columella itself, not one of the folds, forms the left hand border of the siphonal canal.

The apertural lirations in Thaluta, Vexillum and Pusia do not continue far into the shell. Some Vexillum species have lirations as juveniles, which can be seen by breaking shells, but these lirations usually stop somewhere in the penultimate whorl, and there is a discontinuity before the apertural lirations are produced. Some Pusia species and all Thaluta species have the adult lirations, but lack juvenile ones. The apertural lirations in all three genera lie at an angle to the growth lines of the shell, being closest to the labrum posteriorly, and farthest from it anteriorly. In some species of Vexillum the juvenile lirations are beaded, whereas in other species they are continuous. Further study of these internal structures may yield phylogenetically informative characters. The apertural lirations apparently are a defense against predation, since shells are often found with the lip broken back flush to the lirations.

Another genus with which Thaluta might at first be confused is Zierliana Gray, 1847. The type species, Voluta ziervogelii Gmelin, 1791, is readily distinguishable from species of Thaluta by its pyriform shape, prominent columellar Iirae, well-developed spiral cords on the lower bodywhorl and larger adult size. Another species regularly placed in Zierliana , however, is Z. anthracina (Reeve, 1844) (figs. 14, 15), and this might more easily be confused particularly with T maxmarrowi. The former may be distinguished from T maxmarrowi and T takenoko n. sp. by its larger size (18 .5 mm length, n = 7, mixed juvenile and adult specimens in ANSP), small paucispiral protoconch, regular mitriform shape in adults and lack of axial ribs. In addition, the labral Iirae of Z. anthracina terminate at the thickened labral margin, rather than obliquely within the aperture as in Thaluta, and the slight constriction of the aperture in its uppermost part by a single spiral process on the columella that is characteristic of Zierliana is present.

Etymology: Thaluta is a fusion of Thala and Voluta , the overall shape being similar to Thala, but the aperture profile and columellar folds resembling those of some volutids. The Japanese genus name Nomi-tetsu-yatate-zoku is here selected for Thaluta.

Thaluta maxmarrowi (Cernohorsky, 1980) (Figs. 1-2)

Thala maxmarrowi Cernohorsky, 1980: 148-149, figs. 25, 26 (not specimen from Lord Howe Island); Cernohorsky, 1988: 83; Drivas & Jay, 1988: pl. 38, fig. 8; Tsuchiya, 2001 : 574, fig. LIS; Turner &

Callomon, 2001: fig . 13 (not figs. 14-15).

Description: Shells to 10.1 mm, average 7.1 mm (n = 28 adults). Juveniles slender, mitriform; ape1ture patulous anteriorly in adults. Tall, conical protoconch of 4.0 to 4.6 whorls, smooth and

New Genus and Species of Costellariidae

Figs. 1, 2. Thaluta maxmarrowi (Cemohorsky, 1980). Holotype, AIM TM-1364, 6.9 mm length. Fig. 3. Thaluta sp. Lord Howe Island, Australia. AMS C-1 14473, 4.8 mm length.

119

Figs. 4, S, 6. Thaluta sp. Off Murray Island, Torres Strait, Australia, AMS C-048463, 4.1, 4.3 & 4.5 mm length.

Fig. 7. Thaluta takenoko sp. nov. Protoconch of paratype 5. Off Minabe, Wakayama Prefecture, Japan. 5.4 mm length.

glossy, pale brown with distinct dark brown band immediately below suture. Protoconch set at 5 to 30°angle to teleoconch. Teleoconch whorls 3.8 to 4.9 with axial ribs of varying definition and density, increasing in number from 15 to 21 on fi rst whorl to 35 to 42 on body whorl, but decreasing in strength. Fine spiral cords over entire teleoconch, with more than 40 on body whorl; spiral cords obsolete on spire in some specimens; stronger and more widely spaced in anterior half of body whorl. Aperture with thin, curved outer margin, lower portion becoming broadly flared in adult specimens, with sinuous posterior margin. Parietal callus thin and glossy in juveniles, thickened with pronounced margin in adults. Four strong plicae on coJumella. Single

120 G. Rosenberg & P. Callomon

oblique row of 13 to 19 long, apertural lirations on labral wall of aperture in adult specimens. Ground color of teleoconch pale straw to mid brown, often with patterning of paler or white blotches usually arranged in ragged spiral band at upper mid-whorl. Soft parts unknown.

Type locality: Seragaki, Okinawa, Ryukyu Islands, Japan, 35 m. Holotype: AIM TM-1364, 6.9 mm [not seen, digital image examined]. Material examined: all dead collected. South Africa: NE of Dog Point, Zululand, South

Africa, 27°04.8'S, 32'53.5'E, 65 m, NMSA 58869, 7.3 mm. Mascarene Islands, Reunion: Baie de Possession, 40-45 min black sand, J. C. Martin collection, 8.6 & 8.5 mm; Baie de Possession, J. C. Martin Collection #2793, 7.7 & 7.3 mm; sta. DC126, 20' 52'S, 55' 38'E, 110 m, MNHN, 7.6 & 6.8 mm; sta. DC85 , 21 °00'S, 55°15'E, 58-70 m, MNHN, 8.6, 8.2, 7.6, 7.3, 7.2, 6.9, 6.9, 6.5, 6.1, 5.9 & 5 .7 mm; sta. DC86, 20°59'S, 55°15'E, 75-90 m, MNHN, 4.3 mm; sta. DC56, 21 ° OS'S, 55°12'E, 170-225 m. MNHN, 6.4 mm; sta. DC176, 21 °02'S, 55°ll'E, 165-195 m. MNHN, 8.0 mm; 58-70 m, UF 137443, 10.l mm; Boucan Canot, St. Denis, sand dredge, 60 m, MNHN, 4.0 mm, juvenile; Boucan Canot, St. Denis, sand dredge, 55 m, A. Deynzer Collection, 7.6 mm. Japan: 1 km WNW of Onna, Okinawa Island, Japan, 26°29.8'N, 127°50.?'E, 45 m, AMS C335850, 5.3 mm; Bolo point [Cape Zanpa], Okinawa Island, Japan, 43 m, 8.5 mm; Tsuchihama, northern Amami Oshima, southwestern Japan, in tidal drift, K. Noda coll., 9.3 mm.

Distribution: South Africa and Reunion; Japan, from Amami Oshima south to Okinawa; reported from the Marshall Islands by Turner & Callomon (2001); depth range, 43 to 225 m.

Discussion: Thaluta maxmarrowi is relatively consistent in morphology throughout its geographic range. Almost the full gamut of sculptural variation is present in a group of specimens from Reunion (MNHN, sta. DC85), and specimens from Okinawa and South Africa also fit within these morphological parameters. The specimen from South Africa constitutes a geographical range extension for the species. The record of Thaluta maxmarrowi from Lord Howe Island by Cernohorsky (1980, paratype 3, Lord Howe Island, off eastern Australia, 31°38.2'S, 159°3.6' E, 44 m. AMS C-114473: Fig. 3) is doubtful. Although this specimen is a paratype, it does not fit comfortably within the range of morphological variation of the species, being smaller than any other known adult specimen (4.8 mm versus 5.4 to 9 .8 mm, excluding protoconchs) and having coarser spiral sculpture, weaker axial sculpture and a darker spiral band in the spire. This specimen is however similar to specimens from the Torres Strait (Figs. 4-6), which may be an undescribed species of Thaluta; these are discussed further under Thaluta takenoko sp. nov.

The protoconch morphology of T maxmarrowi is consistent in all the material examined. The specimen figured by Tsuchiya (2001: 574, fig . 115) seems on first sight to have a shorter, more bulbuous protoconch, but it is apparently incomplete. The unusual white staining also observable within the aperture of this specimen apparently represents partial delamination rather than a porcellaneous shell layer.

Thaluta takenoko n. sp. (Figs. 7-13)

Thala maxmarrowi: Turner & Callomon, 2001: figs. 14, 15 (not of Cernohorsky, 1980).

Description: Shell small, to 5.9 mm, regular mitriform in juvenile specimens, aperture expanding anteriorly in adults. Protoconch of 1.3 to 1.5 whorls, smooth, translucent. Teleoconch of 4.0 to 4.3 whorls. Early teleoconch whorls bear smooth axial ribs, these weakening pro­gressively and usually becoming obsolete before body whorl. Holotype has 34 weak axial ribs on body whorl. Whorls straight-sided or moderately inflated, suture slightly impressed. Numerous very indistinct spiral cords on teleoconch, becoming more apparent on body whorl. S ix to eight strong spiral cords on lower third of body whorl; cords reflected as grooves within lower aperture

New Genus and Species of Costellariidae 121

Figs. 8-13. Thaluta takenoko sp. nov. 8. Holotype, ANSP 410355, Ogokuda beach, Kushimoto District, Wakayama Prefecture, Japan, 5.4 mm length. 9. Paratype 1, NSMT-Mo 73573, from type locality, 5.9 mm length. 10. Paratype 2, off Minabe, Wakayama Prefecture, Japan, 5.9 mm length. 11. Paratype 4, off Minabe. 4.7 mm. 12. Paratype 5, off Minabe, 5.4 mm length. 13. Paratype 3, off Minabe, 5.4 mm. Paratypes 2-5, all K. Noda collection.

F igs. 14, 15. Zierliana anthracina (Reeve, 1844). Mindoro Island, Philippines, ANSP 335589, 17.6 mm length.

122 G. Rosenberg & P. Callomon

of juvenile specimens. Columella with four strong plicae that terminate abruptly at margin of parietal callus. Parietal callus thickened in adult specimens, with distinct margin. Outer apertural margin thin and fragile in juveniles, lower portion flaring outward in adults as typical of genus. Single oblique row of 9 to 10 short, polished teeth on inner labral wall of aperture. Shell dark brown overall, with occasional patterning of paler blotches that are often linked. Single darker brown band present at or slightly below suture in early whorls of most specimens. Soft parts unknown.

Type locality: Ogokuda beach, Kushimoto District, Wakayama Prefecture, Kii Peninsula, Honshu, Japan. In tidal drift.

Type material: Holotype. Leg. K. Noda. ANSP 410355, length 5.4 mm, width 2.1 mm. Paratypes.1) From the type locality, Leg. K. Noda, NSMT-Mo 73573, 5.9 mm, 2) Off Minabe, Wakayama Prefecture, in shrimp nets, approx. 20 m, 27 Feb. 2001. K. Noda collection, 5.9 mm. 3-5) Off Minabe, Wakayama Prefecture, in shrimp nets, approx. 20 m, 2 Feb. 1999, K. Noda collection, 5.4, 4.7 & 5.4 mm.

Distribution: At present known only from the southern Kii Peninsula, central Japan. Live from approximately 20 m, dead shells in beach drift.

Etymology: Takenoko (Japanese), an infant bamboo shoot, for the shape and color. The Japanese name Ogokuda-yatate is here selected for the species.

Discussion: The protoconch of Thaluta takenoko (Fig. 7) comprises 1.5 or fewer whorls, and is both more bulbous and thinner in construction than that of T ma.xmarrowi (Fig. 2), which is 4.0 whorls or more. Thaluta takenoko is usually smaller than T. maxmarrowi, the largest adult of the former being the size of the smallest adult of the latter (5 .9 mm), has fewer apertural lirations, 9-10 versus 13-19, and lacks axial sculpture on the body whorl. The color patterns are similar in having pale blotches between the suture and periphery, especially on the body whorl, but T. takenoko has a darker ground color and lacks the axial flares and lines that contribute to the blotching in T. maxmarrowi.

The difference between the protoconchs of these species reflects a presumed difference in their modes of larval development, with T. maxmarrowi undergoing a relatively Jong planktotrophic phase and T. takenoko lacking a planktonic phase. This idea is supported by the broad disttibution of T. maxmarrowi and the narrow peripheral range of Thaluta takenoko.

Two lots comprising five specimens from the Torres Strait, Queensland, Australia display some teleoconch characters of both T. maxmarrowi and T. takenoko (off Darnley Island, Torres Strait, 9° 35'S, 143°46'E, 18 m, AMS C-335849, 4.4 & 3.8 mm; off Murray Island, Torres Strait, 9°56 ' S, 144°4 'E, 9-15 m, AMS C-048463, 4.1, 4.3 & 4.5 mm). Three specimens are apparently adults (Figs. 4-6), with apertural Iirations, a thickened parietal shield and evidence of an expanded aperture; however, they are smaller in size (average 4.3 mm) than adult T. takenoko (average 5.7 mm, n = 3) and have a smaller number of teleoconch whorls, 3.5 versus 4.1. They bear more distinct axial ribs than T. takenoko, more closely resembling T. maxmarrowi in this respect. All are lighter in color than fresh T. takenoko but are worn to a varying extent; at least three bear the distinctive dark brown subsutural band. All five lack protoconchs, in the absence of which further definition is not possible, but they are here provisionally separated from the two other species as Thaluta sp.

Acknowledgments

The authors are grateful to Mr. Kazutaka Noda of Gobo, Wakayama Prefecture, Japan for donating some of the type material of T. takenoko, and for providing specimens of T maxmarrowi for examination. Thanks are also due to Mr. A. Deynzer of Sanibel, Florida, Mr J. C. Martin of Reunion, Dr. Philippe Bouche! (MNHN) and Mr. Ian Loch and Dr. Winston F. Ponder (AMS) for loans of material. Mr. T. J.

New Genus and Species of Costellariidae 123

Landers of the Auckland War Memorial Museum provided the figures of the bolotype of T. maxmarrowi.

References

Cemoborsky, W 0. 1980. The taxonomy of some lndo-Pacific Mollusca. Part 8. Records of the Auckland Institute and Museum 17: 135-152.

Cemohorsky, W 0. 1988. The Mitridae, Costellariidae and Nassariidae (Mollusca: Gastropoda) recently dredged at Reunion Island, Indian Ocean, with descriptions of new species. Records of the Aucklnnd Institute and Museum 25: 75-85.

Drivas, J. & Jay, M. 1988. Coquillages de La Reunion et de l'fle Maurice. Delachaux et Niestle: Neucha­tel, Paris. 160 pp.

Rosenberg, G. & Salisbury, R. 2003. On Mitromica and Thala (Gastropoda: Costellariidae) with descriptions of new species from the Western Atlantic and lndo-Pacific. Notulae Naturae 478: 1-30, 118 figs.

Tsuchiya, K. 2001. Costellariidae. ln T. Okutani (ed.), Marine Mollusks in Japan, pp. 556-575. Tokai University Press, Tokyo.

Turner, H. & Callomon, P. 2001. New records of mitriform gastropods from Japan with description of Vexillum (Pusia) charlesi n. sp. (Neogastropoda: Muricoidea: Costellariidae). Venus 60: 7-14.

(Received January 4, 2003 I Accepted October 6, 2003)

124 G. Rosenberg & P. Callomon

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