radiolaria - rads_cat - Siphostichartus praecorona

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Other pages this level: S. jahnae, S. praecorona

Siphostichartus praecorona

Citation: Siphostichartus praecorona Nigrini 1977

Type repository: Holotype, 778-32-2, A-R43/2; paratype. 77B-32-2, B-R39/2 (?) U.S. National Museum, Washington, D.C.

Family (traditional): Artostrobiidae

Four-segmented form with a smooth, thin-walled shell. Cephalis small, hemispherical, with a few small circular pores; short, apical horn may be present; vertical tube generally short, cylindrical, but forms transitional between S. praecorona and S. corona have a well-developed, but not flamboyant, duck-billed tube. Thorax inflated, slightly heavier than rest of shell with three transverse rows of circular pores. Abdomen may appear as a "neck" on the fourth segment or may be a discrete, but short segment with two or, as the form approaches S. corona, three or four transverse rows of circular pores. Termination ragged. Distinguishing characters (rw): This species is similar to Phormostichoartus marylandicus, but the fourth segment is more inflated and intersegmental strictures are more pronounced.
Riedel and Sanfilippo (1971) noted and illustrated this species as Phormostichoartus sp.aff. P. corona. The specimen figured by them (pl.2J, fig.6) is a good example of what is herein called "transitional," with a well-developed vertical tube but only two pore rows on the abdomen. The specimen shown on plate 2J, figure 5 may also be "transitional" and could be called either S. corona or S. praecorona.
The prominently "necked" forms illustrated by Riedel and Sanfilippo (pl.3F, figs. 4, 5) are excluded from the present description because they have not been observed by this author. They have been described by Petrushevskaya and Kozlova (1972, p.539, pl.23, figs. 26,27) as Theocamptra formaster Petrushevskaya.
The specimen shown by Riedel and Sanfilippo (1971, pl.3F, fig.6) does not appear to have four segments and is also excluded.

Precursor of S. corona and closely related to Phormostichoartus marylandicus, the precursor of P. doliolum.

References:

Nigrini, C. A. (1977). Tropical Cenozoic Artostrobiidae (Radiolaria). Micropaleontology. 23(3): 241-269. gs

CATALOG OF ORIGINAL DESCRIPTIONS: Siphostichartus praecorona Nigrini 1977

Siphostichartus praecorona

References:

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