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Lampromitra cracenta
Takahashi, 1991
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Description - Add description
Benson, 1966, p. 452-455; pl. 30, figs. 9-10 (not fig. 8):
Lampromitra cf. coronata Haeckel (partim.)
?Lampromitra coronata Haeckel, 1887, Challenger Rept., Zool. vol. 18, p. 1214, Pl. 60, fig. 7,7a.
?Sethophormis pentalactis Haeckel, 1887, Challenger Rept., Zool., vol. 18, p. 1244, Pl. 56, fig.5.
Low, smooth, conical test consisting of a cap-shaped cephalis which is separated from the broadly conical thorax by a change in contour or a very slight stricture occupied by ribs corresponding to the apical-lateral and ventral arches of the collar ring. Pores of cephalis subequal, subcircular, about 2-3 times as broad as the intervening bars. Thorax proximally with small, irregularly arranged pores about the same size as those of the cephalis; in the middle portion, with large, polygonal pores separated by narrow intervening bars, generally subequal, irregularly arranged but with a tendency toward hexagonal arrangement in transverse rows; distal pores of thorax about the same size or slightly larger than those of the proximal portion, arranged in one or two transverse rows parallel to the thoracic margin and located immediately above an inner septal ring which separates the thorax from a narrow, nearly horizontal flange with one or two rows of pores similar to those at the base of the thorax. Margin of flange with numerous (15-25), thin, conical spines which lie in its plane and extend radially outward; several (10-20 or more), thin, conical spines arise from the inner septal ring and extend vertically downward. Four large collar pores present; cardinal pores of type B; apical bar extends as and is collinear with a short, conical, apical spine that arises from the dorsal stricture between cephalis and thorax and ascends dorsally; vertical bar extends as and is collinear with a short, conical vertical spine that arises from the ventral stricture between cephalis and thorax and ascends ventrally; a short axial spine present; secondary lateral bars absent; dorsal and primary lateral bars free within thoracic cavity but eventually join thoracic wall, and extend as longitudinal thoracic ribs that terminate in relatively short, conical spines that extend beyond and below the mouth of the thorax; in a few tests the primary lateral bars are bifurcated where they join the thoracic wall, and each branch continues in the wall of the thorax as a rib.
Measurements; based on 5 specimens from stations 91 and 133: length of test approximately 50-85 µm; breadth of test 132-209 µm; length of dorsal and primary lateral spines 10-18 µm.
Remarks. The chief distinguishing characters of this species are the low, conical test, thorax with large, irregular, polygonal pores in its middle portion and 1-2 transverse rows of small pores at its base, the inner septal ring, and the small-pored flange. One specimen was observed with smaller thoracic pores that are nearly equal in size, thus not unlike Lampromitra coronata Haeckel (1887,. Pl. 60, figs. 7, 7a). The character of the dorsal and primary lateral bars and thoracic ribs of the Gulf species agrees well with L. coronata Haeckel. It differs from this species, however, in the lack of an apical horn twice as long as the cephalis, in generally larger polygonal thoracic pores, and in the presence of a single, not double, horizontal terminal flange. Without reference to Haeckel’s type material of this species positive identification is not possible.
Because the primary lateral thoracic ribs are bifurcated in a few specimens, they are similar to Sethophorrnis pentalactis Haeckel (1887, p. 1244, Pl. 56, fig.5). This species has a single, horizontal flange but smaller, more numerous, polygonal thoracic pores than those of the Gulf specimens.
Distribution. This species is very rare in the Gulf. It is present only at stations 46, 60, 91, 92, 93, 106, 133, and 136. Its absence at marginal stations indicates its preference for offshore, more nearly oceanic waters. Its occurrence as far north as stations 133 and 136 may be the result of its response to upwelling causing diatom blooms in this region, but its frequency at these stations is too low for such a positive statement to be made. It apparently does not have a great affinity for Gulf waters and may be rare in normal oceanic waters as well.
Haeckel reports Lampromitra coronata Haeckel (1887, p. 1214) from the central Pacific at "Challenger" station 271 and Sethophormis pentalactis Haeckel (1887, p. 1244) from the same region at "Challenger" station 266.
| | Benson 1966 | Cephalis cap-shaped with small pores. Thorax with three ribs which penetrate the perimeter and form spines and with coarse irregular polygonal mesh; marginal mesh forms a zone of fine mesh with small circular to subcircular pores. Number of short spines on the perimeter is about 30 and they are conical. The perimeter of the thorax is an irregularly curved circle.
DIMENSION: (5 specimens) Thorax diameter 153-164 µm.
| | Takahashi 1991 |
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