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Lophophaena witjazii
(Petrushevskaya, 1971)
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Description - Add description
Benson, 1966, p. 378-380; pl. 24, figs. 22-23; pl. 25, fig. 1:
Lophophaena cf. capito Ehrenberg
?Lophophaena capito Ehrenberg, 1874, Akad. Berlin, Monatsb. (1873), p. 242; 1876, Akad. Berlin, Abhandl. (1875), Pl. 8, fig. 6.
Bulbous cephalis, smooth except for 3-8 or more generally three-bladed, relatively long accessory spines or horns originating from its broadest part and extending nearly horizontally to vertically; cephalis separated from a broad, smooth, cylindrical thorax by a "necked" region. Pores of both joints similar, circular to subpolygonal or polygonal, equal but relatively small (10-15 on half the largest circumference of the cephalis), hexagonally arranged, in several specimens in vertical rows. Four collar pores present; cardinal pores of type B; vertical bar thinner than median bar. A short, thin, conical vertical spine originates from the collar ring in the neck region. Apical bar a thin dorsal cephalic rib without larger pores disposed on either side of it; the apical spine extending from this rib originates from the dorsal cephalic face and is generally thin and conical but three-bladed in a few tests. Dorsal and primary lateral bars extend as thin, cylindrical to three-bladed thoracic ribs which terminate in very short, indistinct spines just below the change in contour of the upper part of the thorax; in a few specimens these spines are longer and more distinct but not typical of those of Lithomelissa hystrix or L. thoracites.
Measurements; based on 7 specimens from stations 27, 34, 60, and 71: length of cephalis 55-76 µm, of thorax 49-74 µm; breadth of cephalis 42-74 µm, of thorax 80-97 µm; length of apical spine 12-49 µm, of vertical spine 6-9 µm, of accessory cephalic spines or horns 6-50 µm, of dorsal and primary lateral spines 2-12 µm.
Remarks. The light-bulb shape of the cephalis, the accessory cephalic spines or horns, the distinct necked region, and the relatively smooth surface and small, equal pores of both joints serve to distinguish this species. Ehrenberg (1876, P1. 8, fig. 6) illustrates a species from the Eocene or Oligocene of Barbados, Lophophaena capito, that has a cephalis and partially developed thorax similar to those of the Gulf species. It differs from the latter in the presence of smaller pores separated by wider intervening bars. His illustration also shows a conical dorsal spine originating from the cephalis immediately below the collar stricture. The primary lateral and dorsal bars of the Gulf species extend as thoracic ribs which terminate subterminally on the thorax as short, inconspicuous spines; therefore, this species has affinity for, if it does not actually belong in, Lithomelissa Ehrenberg. The genus Lophophaena Ebrenberg is similar to Lithomelissa except that radial apophyses are absent. Because the dorsal and primary lateral spines originating from the thoracic ribs are inconspicuous, the Gulf species is placed in Lophophaena with the understanding that the two genera in question are closely related if not congeneric. The Gulf species is also similar to Lophophaena? galeata Ehrenberg (1876, P1. 8, fig. 12) which lacks the dorsal spine. Whether or not this species is conspecific with L. capito cannot be determined without reference to type material. The Gulf species is tentatively identified with the latter because of the common presence of a dorsal, subterminal spine, although in Ehrenberg's illustration this does not extend from a thoracic rib. L. capito is shown with only one cephalic horn, whereas the Gulf specimens have several; a few, however, have weakly developed accessory horns or they are absent. The important similarity between the two species is the shape of the cephalis.
Distribution. This species is rare in the Gulf but occurs as far north as station 184. It is absent north of this station as well as at stations 90, 95, and 130. Its slightly greater frequency and general occurrence in the southern Gulf and its absence in marginal areas indicates its preference for oceanic waters over those of the Gulf.
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