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Botryostrobus auritus-australis (Ehrenberg) group Nigrini, 1977

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Benson, 1966, p. 521-523; pl. 35, figs. 12-13:

Siphocampium cf. seriatus Haeckel

?Lithostrobus seriatus Haeckel, 1887, Challenger Rept., Zool., vol. 18, p. 1474, Pl. 79, fig. 15.

Smooth test with 3-6 (generally 4-5) inflated, truncate-conical or campanulate joints below the hemispherical cephalis. Cephalis with six collar pores at its base, a conspicuous, trumpet-like ventral tube, a dorsal lobe, and a short, stout, three-bladed apical spine. Structure of cephalis and collar region the same as in the other species of Siphocampium from the Gulf. Short, indistinct, dorsal and primary lateral thoracic ribs present. Vertical spine extends within the proximal portion of the interior of the ventral tube. Cephalis appears separated from thorax by a distinct stricture in dorsal or ventral view. Pores of cephalis small, circular, infilled with silica in several specimens. Pores of thorax equal, circular, hexagonally arranged in 3-4 transverse rows, separated by
wide intervening bars. Constrictions between joints deep, coincident with broad hyaline rings with numerous, minute, parallel, longitudinal ridges; internally raised septal rings lacking. Abdominal joints approximately equal in length but increase in breadth distally. Distal joint (generally the fourth or fifth abdominal joint) inflated proximally, cylindrical distally. Terminal margin of last joint incomplete. Pores of abdominal joints similar, small (generally 4-7 Ám), circular to subrectangular, separated by wide intervening bars, arranged in 3-8 (generally 5-6) transverse rows per joint, pores of each row approximately of equal size. In several specimens the pores are nearly completely filled with silica.

Measurements; based on 30 specimens from stations 27 and 34: maximum length of test 96-178 Ám, maximum breadth (generally the distal joint) 57-87 Ám; length of cephalis l5-20 Ám, of thorax 16-25 Ám, of abdominal joints 21-46 Ám; breadth of cephalis 18-25 Ám, of thorax 32-44 Ám, of first abdominal joint 46-58 Ám, of remaining abdominal joints 54-87 Ám; length of apical spine 0-12 Ám, of vertical spine 3-4 Ám, of ventral tube 5-11 Ám.

Remarks. Except for the apparent lack of a ventral cephalic tube, Lithostrobus seriatus Haeckel is identical with the species from the Gulf. Popofsky's text figures 131, 133, 134, 136, 137, and 140 of Lithamphora furcaspiculata Popofsky (1913, pp. 408-412) are similar to the Gulf species but have long internal axial spines. Study of the type material of these species should determine whether or not they are conspecific with the Gulf species.

Distribution. This species is rare but cosmopolitan in the Gulf. It is absent at stations 99, 130, 191, 203, 206, and 214. It occurs with slightly higher relative frequency at stations 56, 64, 95, and 106, and its average frequency in the southern half of the Gulf is slightly greater than that in the northern half. Whether or not it responds to upwelling in the Gulf cannot be determined from the numerical data. It prefers offshore, more nearly oceanic waters.
This species is apparently confined to tropical regions. L. seriatus Haeckel was reported from "Challenger" stations 270-274 in the central tropical Pacific. Popofsky's illustrated specimens mentioned above were reported from the tropical western Indian and central Pacific Oceans.
Benson 1966


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