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Doryconthidium sp. cf. D. hexactis Benson, 1983

Description - Add description

Benson, 1966, p. 146-147; pl. 3, fig. 12:

Doryconthidium? sp.

Test consisting of three concentric shells joined by six mutually perpendicular beams one of which is prolonged into a long, very heavy, three-bladed spine with small serrations on each blade distally; remaining beams either terminate at the cortical shell wall or extend beyond it as short thorns or thin conical spines, 2-33 µm in length; one to three relatively short, three-bladed accessory radial spines, 9-32 µm in length, arise from the surface of the cortical shell between its equator and the pole opposite that of the main spine, in one or more quadrants; in a few tests these spines continue inwards as thin, accessory radial beams. Cortical shell subspherical to slightly flask-shaped, in a few specimens with suboctagonal outline; surface with thorns or short, thin, conical spines arising from the nodes of the intervening bars as well as from along the bars; pores relatively large, separated by thin bars, polygonal to subpolygonal, subequal in size with subregular hexagonal arrangement, 8-11 on the half circumference. Second shell widely separated from cortical shell, spherical with relatively smooth surface, with subpolygonal to subcircular, nearly equal, hexagonally arranged pores, 8-11 on the half circumference. First shell subspherical to subpolyhedral, with 3-4 subequal, polygonal to subpolygonal pores on the half circumference. The radial beams arise from the surface of the first shell, are thin and cylindrical, but become heavier and three-bladed after piercing the second shell.

Measurements; based on 10 specimens from stations 34, 60, 71, 81, 91, 92, and 106: polar diameter of cortical shell 117-135 µm, equatorial diameter of cortical shell 108-135 µm, diameter of second shell 37-41 µm, diameter of first shell 17-21 µm; length of single polar spine 95-148 µm, breadth at its base 18-27 µm.

Remarks. The only species described and illustrated in the literature as having six apparently mutually perpendicular radial beams and a large single polar spine is Dorylonchidium hexactis Vinassa de Regny (1900, pp. 230-231, Pl. 1, fig. 12) which differs from the Gulf species in having only two concentric shells. As it was described from the Miocene of Italy, there is evidence that cubosphaerids with a single polar spine have a relatively long history. Because this species is rare in the Gulf, its complete range of variation was not determined; therefore, a new name for this taxon was not proposed.
Benson 1966











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