Brookula Iredale, 1912

Absalão, Ricardo S., Miyaji, Cintia & Pimenta, Alexandre D., 2001, The genus Brookula Iredale, 1912 (Gastropoda, Trochidae) from Brazil: description of a new species, with notes on other South American species, Zoosystema 23 (4), pp. 675-687: 677-681

publication ID

http://doi.org/10.5281/zenodo.5393905

persistent identifier

http://treatment.plazi.org/id/03B787DD-FFB3-FFC7-FED7-FD4B83A08DFD

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Marcus

scientific name

Brookula Iredale, 1912
status

 

Genus Brookula Iredale, 1912  

Brookula Iredale, 1912: 219   .

TYPE SPECIES. — Brookula stibarochila Iredale, 1912: 220   by original designation (holotype’s photograph in Clarke 1961: pl. 1, fig. 5).

DIAGNOSIS. — Shell small, globose-turbinate, thin, umbilicate, with inflated whorls. Protoconch smooth or sculptured with anastomosing ribs forming microscopic pits or with irregular wart-like concretions. Axial sculpture dominant; raised spiral sculpture welldefined, but weaker, in some species overriding and forming beads at intersections with axial ribs; fine incremental growth lines are present. Suture deeply constricted. Aperture rounded, slightly oblique, with a slightly thickened lip and complete peritreme.

REMARKS

The genus Brookula   was created by Iredale (1912), based on Brookula stibarochila   , to include certain species that he could not place in any other genus of Cyclostrematidae   . Cyclostrema conicum Watson, 1886   , was a member of that group. Clarke (1961) divided the species of Brookula   into three subgenera: Brookula   sensu stricto; Vetulonia Dall, 1913   (type-species: Vetulonia galapagana Dall, 1913   ); and Benthobrookula Clarke, 1961 (type-species: Brookula (Benthobrookula) exquisita Clarke, 1961   ).

Warén (1992) regarded Brookula   as belonging to the family Trochidae   , subfamily Eucyclinae   (sensu Hickman & McLean 1990: 74, 75) and raised the taxon Benthobrookula Clarke, 1961 to generic level, considering it as probably related to Lissotesta Iredale, 1915   , because of the protoconch type shared by both taxa. However, Warén (1992: 170) expressed doubts whether that type of protoconch is a “synapomorphy or caused by modification in the larval development”. The subfamily Eucyclinae   is largely characterized by the radulae (diagnosis in Hickman & McLean 1990), but we have no information about radulae from local Brazilian Brookula species.   In the other hand, the radulae of B. powelli   ( Clarke 1961: pl. 4, fig. 9) seems to fit well within the definition given by Hickman (1998: 680) for this subfamily. Therefore, we follow Hickman & McLean (1990) in considering the genus Brookula   as included in the subfamily Eucyclinae   , but regard all species herein treated as belonging to the genus Brookula   sensu lato, because of the insufficiently well-established supraspecific classification, even in a conchological sense.

Among the South American species of Brookula   , there are two or perhaps three recognizable kinds of protoconch sculpture. Brookula calypso   , B. powelli   and B. exquisita   have protoconchs consisting of a surface covered by very low, irregular wart-like concretions ( Fig. 1B, D, F View FIG ). This kind of protoconch ornamentation differs from that found in the three species discussed in this paper ( B. conica   , B. pfefferi   , and B. spinulata   n. sp.), which consists of very fine and densely crowded anastomosing ribs, forming microscopic pits in a somewhat alveolar pattern ( Figs 2F, G View FIG ; 4 View FIG E-G; 5G). A third pattern seems to be present in the topotype of B. stibarochila   (figure in Warén 1992: 224, fig. 23B), which shows an apparently smooth protoconch surface.

Beside the Brazilian species reported herein, additional species from southwestern Atlantic and adjacent Antarctic waters have been, elsewhere, referred to Brookula   . We give a brief summary of some of them:

1. Cyclostrema liratula Pelseneer, 1903   and Cyclostrema humile Pelseneer, 1903   , were includ- ed in Brookula   by Carcelles (1953). However, these species do not fit the genus Brookula   as defined herein, since they lack axial sculpturing and have only spiral sculpture. Both species were referred to Lissotesta Iredale, 1915   by Warén (1992);

2. Brookula crassicostata ( Strebel, 1908)   . Described from 54°43’S, 064°08’W, 36 m. According to a syntype (ZMH), B. crassicostata   shows no trace of spiral sculpture, having only low and strong rounded ribs. This species was illustrated by Castellanos & Landoni (1989: 12, fig. 1a, b, c) and, according Warén (in litt.) this species fits in the Liotella Iredale, 1915   concept; 3. Brookula decussata   ( Pelseneer, 1903: 19, pl. 5, fig. 48). Described from the Bellingshausen Sea (70ºS, 080º48’W, 500 m). The type for this species has not been located, and our comparisons to the Brazilian species are based on the original description and figure;

4. Brookula rossiana Dell, 1990: 102   , fig. 169 and Brookula antarctica Dell, 1990: 102   , fig. 170. Both described from the Ross Sea, at 362 m. Although the original description of B. rossiana   fits very well in our concept for B. pfefferi   , considering the scope of variation we found in the latter, we do not feel secure to consider them co-specific since we could not exam the holotype of B. rossiana   and the original figure provided by Dell (1990) does not allow a precise evaluation of their conchological characters. On the other hand, the description of B. antarctica   suggests it to be distinct enough to be consider as a valid species; 5. Brookula lamonti Clarke, 1961: 357   , pl. 4, fig. 3. Described from the Scotia Sea, around 96 km south of South Georgia, at 3758 m. Although the holotype (MCZ 225963) is only a shell fragment, some parts of the shell sculpture, the aperture (partly broken), and the umbilicus are still visible. The narrow umbilicus and the somewhat posteriorly angled aperture are the distinctive characters, although the sculpture pattern shows no distinctions from B. pfefferi   ;

6. Brookula calypso   ( Melvill & Standen, 1912: 345, fig. 3). Described from Burdwood Bank, 54°25’S, 057°32’W (at 102 m). We illustrate the holotype ( RSM 143.599 View Materials ) ( Fig. 1A, B View FIG ) GoogleMaps   ; 7. Brookula powelli Clarke, 1961: 355   , pl. 3, fig. 7; pl. 4, figs 1, 9. Described from the mid- Argentine Basin, around 1609 km east-southeast of Buenos Aires, at 4587 m. We illustrate the holotype ( MCZ 224960 View Materials ) ( Fig. 1C, D View FIG ). There are also paratypes at MCZ and NMC   ;

8. Brookula exquisita Clarke, 1961: 356   , pl. 3, fig. 8; pl. 4, fig. 2. Described from around 96 km south of South Georgia, at 3758 m. We illustrate the holotype ( MCZ 225964 View Materials ) ( Fig. 1E, F View FIG ). There is also a paratype at NMC 4742   .

Brookula conica ( Watson, 1886)   ( Fig. 2 View FIG )

Cyclostrema conicum Watson, 1886: 122   , pl. 8, fig. 9.

Brookula conica   – Rios 1994: 39, pl. 12, fig. 128.

TYPE MATERIAL. — Three syntypes ( BMNH 1887. 2.9.432).

TYPE LOCALITY. — Off Pernambuco, Brazil, stn 120, 08°37’S, 034°28’W, 1235 m. — Stn 122, 09°05’S, 034°50’W, 640 m.

MATERIAL EXAMINED. — The photograph of the syntype herein figured and:

PADCT. [15], 28°00.05’S, 046°59.67’W, 490 m, 29.XI.1997 ( IBUERJ 1519: # 6608) GoogleMaps   ; [50], 27°10.38’S, 047°27.54’W, 129 m, 09.XII.1997 ( IBUFRJ 10872: # 6635) GoogleMaps   ; [20], 24°17.13’S, 044°12.15’W, 163 m, 10.I.1998 ( MNRJ 8423 View Materials ) GoogleMaps   ; [25], 25°15.76’S, 45°04.62’W, 124 m, 21.XI.1997 ( MORG 41033: # 6577) GoogleMaps   ; [2], 23°35.82’S, 041°42.42’W, 143 m, 15.XI.1997 ( MZSP 32480 View Materials : # 6541) GoogleMaps   ; [225], 24°12.74’S, 044°58.98’W, 79 m, 20.XI.1997 ( MZSP 32481 View Materials : # 6571) GoogleMaps   ; [3], 24°42.61’S, 044°43.42’W, 155 m, 20.XI.1997 ( MZSP 32482 View Materials : # 6573) GoogleMaps   ; [25], 25°15.76’S, 45°04.62’W, 124 m, 21.XI.1997 ( MZSP 32483 View Materials : # 6577) GoogleMaps   ; [5] (24°42.30’S, 045°18.83’W, 84 m, 21.XI.1997 ( MZSP 32484 View Materials : # 6579) GoogleMaps   ; [2] 25°17.66’S, 046°21.16’W, 81 m, 26.XI.1997 ( MZSP 32485 View Materials : # 6587) GoogleMaps   ; [55], 26°23.55’S, 046°39.49’W, 175 m, 27.XI.1997 ( MZSP 32486 View Materials : # 6595) GoogleMaps   ; [68], 27°48.07’S, 047°24.04’W, 175 m, 29.XI.1997 ( MZSP 32487 View Materials : # 6606) GoogleMaps   ; [14], 28°00.05’S, 046°59.67’W, 490 m, 29.XI.1997 ( MZSP 32488 View Materials : # 6608) GoogleMaps   ; [2], 23°57.99’S, 043°52.56’W, 133 m, 07.XII.1997 ( MZSP 32489 View Materials : # 6627) GoogleMaps   ; [51], 27°10.38’S, 047°27.54’W, 129 m, 09.XII.1997 ( MZSP 32490 View Materials : # 6635) GoogleMaps   ; [1], 25°49.30’S, 046°34.00’W, 128 m, 11.XII.1997 ( MZSP 32491 View Materials : # 6642) GoogleMaps   .

REVIZEE. [1], 25°51.04’S, 045°47.30’W, 206 m, 15.XII.1997 ( MZSP 32492 View Materials : # 6652) GoogleMaps   ; [9], 25°43.50’S, 046°02.50’W, 155 m, 15.XII.1997 ( MZSP 32493 View Materials : # 6653) GoogleMaps   ; [1], 24°17.68’S, 043°48.20’W, 314 m, 09.I.1998 ( MZSP 32494 View Materials : # 6660) GoogleMaps   ; [150], 24°00.95’S, 043°55.54’W, 135 m, 09.I.1998 ( MZSP 32495 View Materials : # 6662) GoogleMaps   ; [4], 24°26.48’S, 044°06.55’W, 500 m, 10.I.1998 ( MZSP 32496 View Materials : # 6664) GoogleMaps   ; [30], 24°17.13’S, 044°12.15’W, 163 m, 10.I.1998 ( MZSP 32497 View Materials : # 6666) GoogleMaps   ; [3], 23°55.40’S, 044°24.45’W, 107 m, 10.I.1998 ( MZSP 32498 View Materials : # 6668) GoogleMaps   ; [22], 24°07.42’S, 044°42.22’W, 101 m, 11.I.1998 ( MZSP 32499 View Materials : # 6669) GoogleMaps   ; [2], 24°32.91’S, 044°27.46’W, 260 m, 11.I.1998 ( MZSP 32500 View Materials : # 6671) GoogleMaps   ; [1], 24°40.75’S, 044°50.82’W, 137 m, 12.I.1998 ( MZSP 32501 View Materials : # 6677) GoogleMaps   ; [1], 25°10.00’S, 044°56.65’W, 167 m, 12.I.1998 ( MZSP 32502 View Materials : # 6681) GoogleMaps   .

REDESCRIPTION

Shell trochiform, reaching 1.8 mm in height, 1.83 mm in width; spire elevated, umbilicate, color white. Protoconch globose, around one and a half whorls, about a half emerged from first teleoconch whorl, and sculptured with fine, densely crowded anastomosing ribs forming microscopic pits in a somewhat alveolar pattern. Teleoconch with up to two whorls, with convex profiles. Suture deep. Axial sculpture consisting of heavy, narrow, slightly prosocline axial ribs (19 on last whorl of syntype, illustrated herein), ribs continuing through base of shell, reaching umbilical region; microscopic axial lines present through interspaces. Spiral sculpture formed by about 20 (last whorl + base) prominent, thin, regularly spaced, revolving cords, cords crossing axial ribs; spirals forming no stronger cords surrounding umbilicus. Aperture rounded, holostomate. Umbilicus large, circular, deep. Outer lip thin.

REMARKS

Brookula conica   is the only member of the genus previously recorded off Brazil, and seems to be one of the few Brookula species   associated with tropical environments.

The type series of B. conica   includes three syntypes, two of them broken (K. Way in litt.). Although we had access to a photograph of only one of the type specimens of B. conica   ( Fig. 2A View FIG ), which is glued on a piece of cardboard and does not show the spire, protoconch, or sculpturing, the original description and illustrations ( Watson 1886) provide good representation of this species. This allowed us to recognize a large number of shells of B. conica   from different localities along the Brazilian coast, and to redescribe the species. Our redescription includes several characters not mentioned by Watson (1886), such as the protoconch microsculpture ( Fig. 2F, G View FIG ), minor details of the shell sculpture ( Fig. 2E View FIG ), and an evaluation of the variability in shell shape (h/w varying from 0.9 to 1.11, see Table 1). We found that the number of axial ribs varies from 15 to 27 ( Table 1), which fits well with the number (15- 25) reported by Watson (1886).

Brookula conica   can be distinguished from all other species previously reported from the South Atlantic by the absence of keels or spiral cords bordering or entering the umbilicus ( Fig. 2B View FIG ).

Kingdom

Animalia

Phylum

Mollusca

Class

Gastropoda

Order

Seguenziida

Loc

Brookula Iredale, 1912

Absalão, Ricardo S., Miyaji, Cintia & Pimenta, Alexandre D. 2001
2001
Loc

Brookula conica

RIOS E. C. 1994: 39
1994
Loc

Brookula

IREDALE T. 1912: 219
1912
Loc

Cyclostrema conicum

WATSON R. B. 1886: 122
1886