Brookula spinulata, Absalão & Miyaji & Pimenta, 2001

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 : 685

publication ID	https://doi.org/ 10.5281/zenodo.5393905
persistent identifier	https://treatment.plazi.org/id/03B787DD-FFBB-FFCB-FECF-FD2F83618FFD
treatment provided by	Marcus
scientific name	Brookula spinulata
status	sp. nov.

Treatment

Brookula spinulata View in CoL n. sp.

( Fig. 5 View FIG )

TYPE MATERIAL. — Holotype ( MNRJ 8424 View Materials ); paratypes (two shells in each lot) ( MNRJ 8425 View Materials ; MORG 41032 ; MZSP 32511; IBUFRJ 10873; USNM 880655; MCZ 320998; MNHN; ZMA 4.01.013; MACN 34733 View Materials ). All types from type locality, except: MORG 41032 and MZSP 32511: PADCT # 6625, 24°29’S, 043°37.4’W, 980 m, 06.XII.1997; and MCZ 320998: PADCT # 6643, 25°25.2’S, 046°04’W, 120 m, 11.XII.1997. GoogleMaps

TYPE LOCALITY. — South of Abrolhos Bank, 19°38.5’S, 038°43’W, 775 m, 19.IV.1995 (JOPS # 3229).

ETYMOLOGY. — From Latin spinula: small spine; - atus: abundant, referring to the small spine-like projections formed at the intersections of the spiral and axial ornamentation.

DESCRIPTION

Shell trochiform, reaching 1.54 mm in height, 1.52 mm in width; spire elevated, umbilicate, color white. Protoconch globose, around one and a half whorls, about 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 three-quarter whorls, with convex profiles and somewhat flat shoulders next to deeper suture. Axial sculpture consisting of heavy, narrow, slightly prosocline ribs (20 on last whorl of holotype), ribs continuing through base of shell, reaching umbilical region; microscopic axial lines present through interspaces. Spiral sculpture formed by prominent, thin, well-spaced, revolving threads (six on last whorl of holotype), threads crossing axial ribs, forming small delicate spine-like projections; spirals becoming thicker, very close, and numerous on base (12 on base of holotype), and forming two or three stronger cords surrounding umbilicus. Aperture rounded, holostomate, slightly elliptical, projecting anteriorly, with flat shoulder next to suture. Umbilicus circular, deep. Outer lip thin.

REMARKS

The microsculpture of the protoconch ( Fig. 5G View FIG ), that consists of very fine and densely crowded anastomosing ribs, forming microscopic pits in a somewhat alveolar pattern distinguishes B. spinulata n. sp. from B. calypso ( Fig. 1B View FIG ), B. powelli ( Fig. 1D View FIG ), and B. exquisita ( Fig. 1F View FIG ). This type of microsculpture is shared with B. conica ( Fig. 2F, G View FIG ) and B. pfefferi ( Fig. 4 View FIG E-G).

Brookula spinulata View in CoL n. sp. is closely related to Brookula pfefferi Powell, 1951 View in CoL , being distinguished by the spine-like nodules formed by the crossing of the axial and spiral sculpture ( Fig. 5A, B, F View FIG ), which are less developed ( Fig. 3C, D View FIG ), or absent ( Fig. 3E, F View FIG ) in B. pfefferi View in CoL ; and by the number of axial ribs on the penultimate whorl (about 33 in B. pfefferi View in CoL ; 20 in B. spinulata View in CoL n. sp.). In addition, the spiral ornamentation in B. spinulata View in CoL n. sp. shows a very constant distribution pattern, with about seven threads on the last whorl ( Fig. 5A, B View FIG ; Table 1) and about 12 (range 9-17) on the base ( Fig. 5D, E View FIG ; Table 1); whereas in B. pfefferi View in CoL , the distribution pattern of spiral threads is variable, with 6-12 on the last whorl ( Fig. 3 View FIG A-C, E; Table 1), and 6-11 on the basal area ( Fig. 4 View FIG A-C; Table 1).

Brookula spinulata View in CoL n. sp. can be distinguished from B. conica View in CoL by the spiral striae, which are weaker in B. conica View in CoL ( Fig. 2E View FIG ), and do not form small spine-like nodules as in B. spinulata View in CoL n. sp. There are strong spiral threads surrounding the umbilicus in B. spinulata View in CoL n. sp. ( Fig. 5D View FIG ); such threads are absent in B. conica View in CoL ( Fig. 2B View FIG ).