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Pterocanium auritum Nigrini and Caulet, 1992

Description - Add description

Benson, 1966, p. 401-403; pl. 26, figs. 5-6:

Pterocanium sp.

Cephalis subhemispherical, smooth or with short spines or thorns; with small, unequal, circular to subcircular pores; separated from the thorax by a distinct change in contour. Two long, conical, cephalic horns, one the apical horn ascending dorsally and extending from the apical bar which is present as a dorsal rib in the wall of the cephalis, the other, an accessory horn, ascending ventrally, both lying in the sagittal plane and fused at their bases. A short, conical, vertical spine generally present. Four collar pores present at the base of the cephalis. Thorax subpyramidal (three nearly flat sides) to nearly campanulate, in a few specimens smooth, in most with scattered thin, conical spines (5-25 µm); with its basal margin turned inward and marked by a continuous internal septal ring. Pores of the thorax subequal but increase in size distally, subpolygonal to subcircular, subregularly arranged. Dorsal and primary lateral bars of the collar region extend as straight divergent ribs in the wall of the thorax and terminate in long, heavy, generally straight, three-bladed feet which originate from the level at which the thorax turns inward distally. Feet not latticed proximally; two blades lie in the genera1 plane of the thoracic wall, each joined by a short bar to the inner septal ring at the base of the thorax. The third blade projects outward and extends from and is generally collinear with the thoracic rib. Abdomen or portions thereof generally present, consists of a lattice developed between the two lateral blades of the feet and the inner septal ring. Pores of the lattice unequal., subregular to irregular in shape and arrangement, as large as or slightly larger than those of the thorax, separated by intervening bars the same width as those of the thorax. In most specimens the distal portion of the abdomen when present is cylindrical, not joined to the feet. Surface of abdomen similar to that of the thorax--smooth to spiny.

Measurements; based on 30 specimens from stations 34, 46, 56, 60, and 151: length of cephalis 18-23 µm, of thorax 49-98 µm, of abdomen (in most specimens rudimentary) 37-141 µm; breadth of cephalis 20-27 µm, of thorax at its widest portion 66-123 µm, of abdomen (distal portion 105-148 µm; length of apical horn 31-81 µm, of accessory horn 25-74 µm, of vertical spine 12-22 µm, of feet 37-234 µm; maximum distance between tips of feet 123-314 µm.

Remarks. The only species of Pterocanium Ehrenberg illustrated in the literature with two cephalic horns is P. bicorne Haeckel (1887, p. 1332, Pl. 73, fig. 5). This species differs from the Gulf species in having a campanulate thorax, feet that are latticed proximally, and a rudimentary abdomen with very small pores. P. orcinum Haeckel (op. cit., p. 1329, Pl. 73, fig. 2) is similar to the Gulf species but has only one cephalic horn. In several specimens from the Gulf one or both horns are absent (apparently broken). Popofsky (1913, pp. 387-388, text fig. 99) illustrated this species but likewise with only one horn. Study of the type material of P. orcinum may reveal that two cephalic horns are present instead of one. Because doubt exists as to whether or not the Gulf species is a new species, a new name is not proposed at this time.

Distribution. This species is cosmopolitan in the Gulf, occurring as far north as stations 191, 192, and 214, although at the last station only two radiolarians were found. It is absent at stations 194, 203, 206, and 208, common at stations 34 (2.2%) and 91 (3.4%, the fifth most abundant species) and rare to nearly common at all others. It undergoes a gradual decrease northward from its maximum at station 91. At this station its increase may be a result of response to upwelling.
Benson 1966
Benson, 1983, p. 507:

Pterocanium bicorne(?)

Remarks. The assignment of this species to Pterocanium bicorne is questionable in light of Nigrini and Moore’s (1979) reservations about applying Haeckel’s species name before examining topotypic material.
Benson 1983











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