Cystammina pauciloculata (Brady, 1879)



Fig. 88. Syntypes of Trochammina pauciloculata, from Brady (1884)


ORIGINAL DESIGNATION: Trochammina pauciloculata Brady, 1879.

TYPE REFERENCE: Brady, H.B., 1879. Notes on some of the reticularian Rhizopoda of the "CHALLENGER" Expedition; Part I. On new or little known arenaceous types. Quarterly Journal of Microscopical Sciences, 19, p. 58, pl. 5, figs. 13, 14.

TYPE SPECIMEN: The holotype specimen of Brady (1879) is housed in the micropaleontological collections of the British Museum (Natural History) and registered as Slide ZF 2508. This specimen was designated the lectotype of the species by Loeblich & Tappan (1964).

TYPE LEVEL: Recent.

TYPE LOCALITY: H.M.S. CHALLENGER Sta. 300, eastern South Pacific, at a depth of 1375 fathoms.

DIAGNOSTIC FEATURES: Test small, streptospirally enrolled. Chambers inflated,enlarging rapidly in size; early chambers are spherical, but later ones become elongated. Four to five chambers are visible from the exterior. Wall imperforate, thin, finely agglutinated, several grains thick, with reddish-brown organic cement. Aperture an areal elongate slit on the dorsal side, above its contact with the oldest exposed chambers.

SIZE: The lectotype has a maximum diameter of 0.50 mm.

SYNONYMS: None verified.

OBSERVED OCCURRENCES: Cystammina pauciloculata is a cosmopolitan species in the bathyal to abyssal regions of the modern ocean. Brady (1884) reported it from 22 CHALLENGER stations from 173 to 3950 fathoms, but the Brady collection includes many specimens of Ammosphaeroidina labelled "Trochammina pauciloculata". Earland (1934) recorded it from 14 stations between 2611 and 4845 m in the Scotia Sea. Pflum & Frerichs (1976) listed it as a typical "middle bathyal" species in the Mississippi Delta region, recording it from depths of 1,506 - 4,584 feet. Lukina (1980) reported it from depths of 3095 - 5050 m in the Central Pacific. Schröder (1986) reported it from the Nova Scotian Continental Rise and Hatteras Abyssal Plain. Kuhnt et al. (2000) illustrated specimens from a depth of 3098 m on the New Jersey margin. We observed the species in samples from the Nova Scotian Continental margin and from the Hatteras Abssal Plain.

KNOWN STRATIGRAPHIC RANGE: Eocene to Recent.

BATHYMETRY: Bathyal to abyssal.

REMARKS: Many of the early reports of this species in flysch-type assemblages can be undoubtedly ascribed to A. pseudopauciloculata, but we have observed specimens with more elongated chambers in middle to late Eocene strata. Some authors have assigned such forms to C. pauciloculata. The relationship between these two species needs to be further investigated. The genus Ammosphaeroidina also extends to the Recent (Brady, 1884, pl. 41, fig. 2). Cystammina sveni may be ancestral to C. pauciloculata, differing in its more rounded chambers and smaller dimensions.

ILLUSTRATIONS: Plate 88 - Cystammina pauciloculata (Brady)
Fig. 1. Recent, CHALLENGER Sta. 300, North of Juan Fernandez, 1375 fathoms, Lectotype designated by Loeblich & Tappan (1964), BM(NH) 1966:2.11.3, ex slide ZF2508; Fig. 2a. Recent, CHALLENGER Sta. 300, Stereo-pair of dissected specimen; Fig. 2b-c. Detail of wall structure; Fig. 3. Recent, CHALLENGER Sta. 300, Stereo-pair of dissected specimen