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Neosemantis distephanus distephanus
Goll, 1979
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Description - Add description
Benson, 1966, p. 291-293; pl. 19, fig. 18; pl. 20, fig. 1:
Neosemantis distephanus (Haeckel) Popofsky
Semantis distepahanus Haeckel, 1887, Challenger Rept., Zool, vol. 18, p. 957, Pl. 83, fig. 3.
Neosemantis distephanus Popofsky, 1913, Deutsche Südpolar-Exped., Vol. 14, p. 299, Pl. 29, fig. 2.
Test consisting of three hemi-cardioid rings, separated by approximately equal angles, meeting at a common point, apically, and arising from the median bar, basally. One ring lies in the sagittal plane and arises from the dorsal end of the short median bar, therefore corresponding to a half sagittal ring; the other two rings arise from the ventral end of the median bar and correspond in position to the primary lateral spines. A thin, three-bladed dorsal spine with short thorns along the blades arises from the dorsal end of the median bar and extends dorsally downward in the plane of the half sagittal ring; a short axial spine or thorn is present; apical and vertical spines are lacking. Median bar generally cylindrical but three-bladed in a few specimens. The three half-rings of similar size and shape, relatively thin, three-bladed, with numerous thorns or thin conical spines of variable length (3-55 µm) arising from the blades, longer spines concentrated near the base of the rings, in a few specimens with one on each lateral ring that may correspond to a primary lateral spine.
Measurements; based on 30 specimens from stations 71, 92, 106, and 133: height of rings 62-103 µm, maximum breadth between two of the rings 52-107 µm, length of dorsal spine 9-64 µm.
Remarks. Haeckel (1887, p. 957) interpreted Semantis distephanus as having a median bar which he states is not drawn distinctly enough in his illustration (op. cit., Pl. 83, fig. 3). Haeckel' s illustration also lacks the dorsal spine, but if this were broken or not fully developed it would have escaped his attention. This species does not have two basal pores but instead three fused half-rings united at two places; therefore, it corresponds to Neosemantis Popofsky, not Semantis Haeckel. For these reasons Haeckel's species is placed in synonymy with Neosemantis distephanus Popofsky. Popofsky's (1913, Pl. 29, fig. 2) illustration of this species agrees in all details with the Gulf species. Popofsky's interpretation differs from mine, however, in that he named the wrong half ring (corresponding to the left primary lateral bar) as the sagittal ring and did not observe the median bar which is distinguishable but only in side view.
Distribution. This species is rare in the Gulf but occurs as far north as station 208, therefore, it is to some extent cosmopolitan but occurs at more stations in the northern half of the Gulf than in the southern half. It is present at stations 60, 64, 81, 91, 92, 93, 106, 115, 133, 151, 184, 191, 192, and 208. It has a slightly greater frequency at stations located within the diatomite facies, but this is not evident in the numerical data. It probably represents a very rare species of the eastern tropical Pacific fauna but occurs throughout the Gulf because of its response to upwelling.
Popofsky reported Neosemantis distephanus from the western tropical part of the Indian Ocean and from the tropical Atlantic Ocean. Haeckel reported Semantis distephanus also from the tropical Atlantic. The occurrence of this species in the Gulf makes it a cosmopolitan tropical species. It has not been reported from high latitudes.
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