| Home> Cenozoic> Holocene (Recent)> Gulf of California>
 

List species

Eucyrtidium erythromystax Nigrini and Caulet, 1992

Description - Add description

Benson, 1966, p. 502-505; pl. 34, figs. 10-12; text-fig. 26:

Lithomitra infundibulum Haeckel

Lithomitra infundibulum Haeckel, 1887, Challenger Rept., Zool., vol. 18, p. 1487, Pl. 79, fig. 5.

Test conical proximally, cylindrical distally, generally smooth, with 3-8 or more (generally 5-6) joints. Cephalis hemispherical, small, with a dorsal sagittal furrow and a short, conical to three-bladed, slightly eccentric apical spine which is less robust than that of Eusyringium siphonostoma and absent in a few tests. A short, vertical spine extends within the interior of a short, inconspicuous, ventral tubule (text-fig. 26). Four collar pores present. Dorsal and primary lateral bars extend as generally indistinct ribs in the wall of the thorax and in some specimens in the proximal portion of the wall of the first abdominal joint; they are rarely present as raised, wing-like ribs as in E. siphonostoma; in a few specimens the ribs are prolonged as short, thin spines (up to 16 Ám). Pores of the cephalis small, circular, equal, in some specimens with infillings of silica. Cephalis separated from a campanulate to truncate-conical thorax by an indistinct stricture or change in contour. Pores of the thorax small but slightly larger than those of the cephalis, equal, circular, hexagonally arranged in longitudinal rows. Thorax separated from first abdominal joint by an indistinct stricture or change of contour and a regular, circular, internal septal ring. First abdominal joint conical, the remaining joints generally cylindrical, in a few specimens the distal joint slightly constricted in its basal portion, but a tubular mouth absent. Abdominal joints relatively long, approximately equal, separated by irregular, generally discontinuous, internal septal rings but also by regular continuous rings in several specimens; a few of the joints separated by slight constrictions as well. Pores of the distal half of the first abdominal joint and the remaining abdominal joints similar, subcircular or elliptical to subpolygonal, nearly equal, larger and less regular than those of E. siphonostoma, arranged in continuous longitudinal rows, 12-16 on half the circumference of the broadest joint.

Measurements; based on 30 specimens from stations 27 and 34: maximum length of test 117-224 Ám, maximum breadth 68-108 Ám; length of cephalis 15-18 Ám, of thorax 18-36 Ám, of first abdominal joint 31-100 Ám, of remaining abdominal joints 22-74 Ám; breadth of cephalis 16-25 Ám, of thorax 30-54 Ám; length of apical spine 0-11 Ám, of vertical spine 1-4 Ám, of ventral tubule 4-7 Ám.

Remarks. Haeckel's illustration and description of Lithomitra infundibulum differs from the Gulf species only in minor details which are variable within the species. These include double-contoured pores and a cephalis without an apical horn. In most Gulf specimens a short, generally inconspicuous apical spine is present, but it is absent in several specimens. Haeckel did not observe thoracic ribs corresponding to the dorsal and primary lateral bars, but in the Gulf specimens the ribs are generally indistinct.

Distribution. This species occurs throughout the Gulf as far north as stations 191 and 192. It is absent at stations 90, 130, l94, and all those to the north. It is common at stations 81 (2.0%), 115 (2.0%), 133 (2.6%), 136 (3.2%), and 151 (2.4%); nearly common but rare at stations 81, 93, 95, and 99; and rare at the others. Its average frequency at stations where it is present is greater in the northern half of the Gulf than in the southern half. This may be explained by its response to upwelling in the northern Gulf because it occurs commonly at stations located within the diatomite facies and is very rare or absent at other stations in this region; therefore, it is not greatly tolerant of waters with higher than average temperature and salinity in the northernmost Gulf. Its slightly higher frequency at stations 71, 91, 93, 95, and 99 in the southern half of the Gulf may be explained by upwelling along either coast. Its absence at marginal localities indicates its preference for offshore, more nearly oceanic waters.
No record of the occurrence of this species other than at "Challenger" station 271 in the central Pacific is known. It is apparently a tropical species.
Benson 1966
Benson, 1983, p. 503:

Eucrytidium infundibulum (Haeckel)

Remarks. Because of its similarity in shape to Eucyrtidium hexagonatum and the presence of an inconspicuous vertical tube on the cep[halis, this species is placed in the genus Eucyrtidium.

Benson 1983


Description

 

Images

 

Synonyms

 

References

 

Distribution

 

Discussion / Comments

 

Web links