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Artostrobium doliolum Riedel and Sanfilippo, 1971

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Artostrobium doliolum Riedel and Sanfilippo, new species (Plate 1H, Figures 1-3; Plate 8, Figures 14, 15)

Description: Spindle-shaped, four-segmented artostrobiids in which the intersegmental strictures are not strongly pronounced externally. Cephalis very small, spherical, bearing a lateral tubule that lies along the thoracic wall and is thus directed obliquely downward. Thorax and third segment truncate-conical; fourth segment the widest, tapering distally, in some specimens with a poreless peristome. All post-cephalic segments with pores in closely-spaced transverse rows.

Measurements based on 30 specimens from 62.1-24-6, 63.0-2-4, 66.1-3-3 and 66.1-4-3. Total length 95 to 150 μ. Maximum breadth 75 to 100 μ (usually about 85 μ).

Remarks: This species differs from all described members of the family in the broadly spindle-shaped form of the four-segmented shell, without very pronounced external strictures. It apparently developed from a form with less developed third segment, more widely separated rows of pores and somewhat more pronounced intesegmental strictures (Plate 1H, Figure 4; Plate 21, Figures 1-8; Plate 3E, Figures 7-9) as we are not yet sure of the phylogenetic development of this form, its assignment to the genus Artostrobium is arbitrary.
Riedel and Sanfilippo 1971


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