Ketosia thomei, Santos, Franklin Noel Dos & Absalão, Ricardo Silva, 2006

Santos, Franklin Noel Dos & Absalão, Ricardo Silva, 2006, A new genus of Barleeidae Gray, 1857 (Mollusca, Gastropoda) and the first occurrence of the genus Pseudodiala Ponder, 1967 off the Brazilian coast, Zootaxa 1232, pp. 59-68 : 62-65

Ketosia thomei new species

( Figs. 6–11 )

Description

Shell conical­pupoid, whorls convex, cream to orange, opaque. Protoconch paucispiral with deep pits. Teleoconch with 3.5 whorls, smooth; with deep pits. Suture impressed. Base rounded. Aperture oval to subcircular. Lip thin, projected backwards. Chink­like umbilicus.

Dimensions

Holotype with 3.5 teleoconch whorls; length 2.1 mm.

Type­material

Holotype: MNRJ 10505. Paratype, 1: IBUFRJ 14696 GEOMAR XVI #16 Am.18, 22º24’4 S 40º55’0 W, 20.viii. 1980, 63 m, “NOAC Coll.”, [1]; paratype 2: MZSP 55460, GEOMAR XVI, #9 Am.11, 22º06’8 S 40º31’2 S, 20.viii. 1980, 59 m, “NOAC Coll.”, [1]; paratype 3: MORG 50447 GEOMAR XVI, #17 Am.19, 22 º27’ S 40º58’ W, 20.viii. 1980, 56 m, “NOAC Coll.”, [2]; paratype 4: MNHN GEOMAR XVI, #17 Am.19, 22 º27’ S 40º58’ W, 20.viii. 1980, 56 m, “NOAC Coll.”, [2]; IBUFRJ 7872: GEOMAR XII #102, 21º38’,8 S 40º14’5 W, 28.viii.1979, “NOAS Coll.” [2]; IBUFRJ 7659: GEOMAR XII #101, 29.viii.1979, “NOAS Coll.” [4]; IBUFRJ 13808 REVIZEE #D3, 22 º52’ S 41º09’ W, 80 m, 23.ii.1996 [1].

Etymology

This species is named in honour of Dr. Wilibaldo Thomé, who has contributed to the knowledge of the Veronicellidae in Brazil and South America.

Discussion

Ketosia , the new genus herein proposed, belongs to Barleeidae because of the presence of minute pits on the protoconch and teleoconch. The distribution of these pits can vary within the family. They may be present on the protoconch in spiral rows, as in Barleeia , Protobarleeia , Fictonoba , and Tropidorissoia ; or they are randomly distributed, as in Caelatura , Lirobarleeia , and Pseudodiala . On the teleoconch, pits are present only in Caelatura ( Table 1 ) but in Ketosia they are less abundant than on the protoconch. Thus, the presence and distribution of pits on both proto­ and teleoconch, besides the unique shell shape, resembling a Halystilus, produce a unique combination of shell characters that does not fit within any known genus of Barleeidae . The position of Ketosia in Barleeidae could not be confirmed with soft part and opercular characters such as minute head with long cephalic tentacles, with eyes localized at the base; pedal sole short, simple; central tooth of radula with one pair of basal denticles, thick marginal teeth and short lateral teeth, and operculum corneus, oval, with or without peg, with excentric nucleus; but the presence of the shell pits makes a placement in Barleeidae most likely.

Representatives of some genera of other families of Rissooidea also have pits on the protoconch or teleoconch: Onoba H. & A. Adams, 1852; Zebina H. & A. Adams, 1854; Pseudotaphrus Cossmann, 1888 ; Boreocingula Golikov and Kussakin, 1974 ; and Gofasia Bouchet & Warén, 1993 , all Rissoidae ; Amphithalamus Carpenter, 1864 ; Anabathron Frauenfeld, 1867 ; Pisinna Monterosato, 1878 ; Nodulus Monterosato, 1878 ; Microdryas Laseron, 1950 ; Badepigrus Iredale, 1955 ; Pseudestea Ponder, 1967 ; and Afriscobris Ponder, 1983, all Anabathridae ( Ponder 1983, 1984; Ponder & Worsfold 1994; Gofas 1995, 1999).

Ketosia does not fit in Anabathridae because this family show a protoconch with spirally arranged pits, and show an umbilicus, and does not fit in Rissoidae because shows spiral and/or axial sculpture (e.g., Alvania Risso, 1826 ), which is not present in Ketosia .

Six species of Barleeidae were previously known from Brazilian waters: Barleeia rubrooperculata (Catellanos & Fernandez, 1972) ; Caelatura barcellosi Absalão & Rios, 1995 ; C. spirocordata Absalão & Rios, 1995 ; C. tigrina Absalão, 2002 ; C. speculabunda Absalão, 2002 ; and Protobarleeia pyrrocincta Absalão, 2002 . None of these can be confused with Ketosia , because the new species belongs to a distinct genus with the surface of the protoconch and teleoconch covered with irregular pits, besides the depression separating the peripheral region of the teleoconch from the inner lip.

Gofas (1995).

Ketosia thomei differs from K. riosi in having less convex whorls (41.8o in K. thomei , 46o in K. riosi ) and having a shorter shell (1.9 mm in K. thomei , 2.2 mm in K. riosi ); K. thomei has a narrow umbilicus, which is absent in K. riosi . In K. riosi the aperture is separated from the teleoconch by a depression not seen in K. thomei . Ketosia occurs off southeastern Brazil, at shallow depths (10 to 80 meters). This agrees with the distributional patterns reported for most species of Barleeidae present off the Brazilian coast.

Figures

FIGURES 6 – 11. Ketosia thomei n. sp. ­ 6: holotype (MNRJ 10505), length 2.1 mm; 7: paratype (IBUFRJ 14696) length 1.8 mm; 8: detail of the teleoconch of holotype; 9: protoconch of paratype (IBUFRJ 14696); 10 – 11: detail of sculpture of the protoconch of paratype (IBUFRJ 14696). Scale bar: 6: 500 m; 7: 200 m; 8: 10 m; 9: 100 m; 10: 20 m; 11: 10 m.

Tables

TABLE 1. Main diagnostic characters of the genera of the family Barleeidae. Sources: Ponder (1983) and

Genus	Form of shell	Protoconch	Teleoconch
Barleeia	conical to oval­ conical	smooth, with pits spirally arranged	smooth or with weak spiral thread
Caelatura	conical­elongated	smooth or with spiral lines, microsculpture of irregular pits	smooth with pits, or with axial or spiral sculpturing
Lirobarleeia	conical­elongated	sometimes with weak spiral ridges, with irregular deep pits,	axially and/or spirally sculptured by threads and nodulous, without pits
Protobarleeia	o v a t e ­ c o n i c	w i t h s p i r a l l i n e s a n d honey comb­shaped pits	with fine, dense, rather irregular spiral threads