Lychnocanoma amphitrite Foreman

Lychnocanoma amphitrite Foreman, 1973, p.437, pl.11, fig.10

DESCRIPTION

Cephalis and thorax similar to L. bellum. Differs in larger size and more massive wall of thorax and relatively shorter feet. Third segment triangular in cross-section, inverted subhemispherical to pyramidal, with very irregular pores. Hollow feet incorporated in shell wall except distally where they protrude outwardly, solid, short, stubby, and bladed (Foreman, 1973).

DIMENSIONS

Based on 20 specimens. Length overall, exclusive of horn 190-280 m, length of cephalis and thorax 140-175 m, of abdomen 40-110 m; greatest width of thorax 150-190 m (Foreman, 1973).

DISTINGUISHING CHARACTERS

Thorax large, hemispherical. Abdomen inverted-hemispherical, with very irregular pores. Three hollow feet mostly incorporated in abdominal wall, distally usually free (Riedel and Sanfilippo, 1978a).

VARIABILITY

Later specimens tend to have the horn become slightly bladed, and very late specimens...have a less robust abdomen with the feet less integrated into the shell wall. Sometimes only a fragment of the third segment is present at the base of the feet (Foreman, 1973).

Specimens have been found where the spongy-walled abdomen is so dense that the hollow feet incorporated in the wall are difficult to discern. A spongy layer may cover the thorax as well (Sanfilippo, unpubl. data).

DISTRIBUTION

This species is found in late Eocene sediments from all oceans. In low latitudes its morphotypic first appearance lies within the Cryptocarpium azyx Zone, but in high latitudes its first occurrence is earlier, in the early Eocene. Its morphotypic last appearance lies within the Theocyrtis tuberosa Zone.

PHYLOGENY

L. amphitrite evolved from L. bellum.

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