Lychnocanoma trifolium (Riedel and Sanfilippo)

Lychnocanium trifolium Riedel and Sanfilippo, 1971, p.1595, p.l.3B, fig.12, pl.8, figs.2-3

Lychnocanoma trifolium (Riedel and Sanfilippo), by implication in Sanfilippo et al., 1973, p.221

DESCRIPTION

Cephalis spherical, poreless, bearing a conical or three-bladed apical horn. Collar stricture pronounced. Thorax campanulate, with smooth surface and subcircular pores generally arranged in groups of three separated by wide poreless areas. Three feet three-bladed, approximately straight, longer than the thorax (Riedel and Sanfilippo, 1971).

DIMENSIONS

Based on 20 specimens. Length excluding horn and feet 75-90 m. Maximum breadth of thorax 75-90 m (Riedel and Sanfilippo, 1971).

DISTINGUISHING CHARACTERS

This species differs from all other members of the genus in the characteristic grouping of thoracic pores in threes (Riedel and Sanfilippo, 1971).

Although some specimens admitted to this species have more pores than does the holotype, all have part of the shell wall (usually the upper part of the thorax) poreless except for scattered groups of three pores (Sanfilippo et al., 1985).

VARIABILITY

Some specimens have a rougher surface than those forming the basis for the original description, as a result of their having a larger number of pores, either still open or secondarily closed. Sometimes the pores in each group of three are fused into one, while retaining their 3-lobed outline, possibly as a result of dissolution (Sanfilippo et al., 1985).

DISTRIBUTION

Lychnocanoma trifolium is a rare, short-ranging species so far recorded only in late late Oligocene assemblages from tropical Pacific and Indian Ocean sequences. Its morphotypic first and last appearances both lie within the Dorcadospyris ateuchus Zone.

PHYLOGENY

Unknown.

REMARKS

Additional illustrations can be found in Ling, 1975, pl.10, fig.12.

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