Podocyrtis (Podocyrtoges) phyxis Sanfilippo and Riedel

Podocyrtis (Podocyrtis) diamesa Riedel and Sanfilippo, 1970, p.533, (pars), pl.12, fig.6

Podocyrtis phyxis Sanfilippo and Riedel, 1973, p.531

Podocyrtis (Podocyrtoges) phyxis Sanfilippo and Riedel, Sanfilippo and Riedel, 1992, p.14

DESCRIPTION

Similar in general form to P. diamesa, but rather stocky, with relatively larger, somewhat more inflated abdomen, and larger pores on both abdomen and thorax. No longitudinal ribs between pores (Sanfilippo and Riedel, 1973).

DIMENSIONS

Total length (excluding horn) 240-385 m; length of abdomen 105-245 m; maximum breadth of abdomen 140-175 m (Sanfilippo et al., 1985).

DISTINGUISHING CHARACTERS

This species is distinguished from its ancestor P. (P.) diamesa by lacking longitudinal ribs on the thorax. The conical horn and thorax are relatively larger than in the superficially similar P. (L.) trachodes (which, in addition, occurs later, has a three-bladed horn, and has a very rough abdominal outline) (Sanfilippo et al., 1985).

VARIABILITY

This species has been found at only very few localities, apparently because of its short stratigraphic range, and it is therefore difficult to distinguish geographic from chronologic variability.

In some assemblages the thoracic outline is smooth and in others it is slightly rough, and the spacing of the abdominal pores varies a little (2.5 - 3 pore centers in 50 m in DSDP 13A-1-1, 130-132 cm to 2.5 - 3.5 pore centers in 50 m in DSDP 149-40-1, 80-83 cm). The lumbar stricture tends to be more distinct in younger assemblages (Sanfilippo et al., 1985)

DISTRIBUTION

This short-ranged, middle middle Eocene species is found only in the Caribbean, the eastern tropical Atlantic and the eastern tropical Pacific. Its evolutionary transition from Podocyrtis diamesa lies within the Thyrsocyrtis triacantha Zone. Its evolutionary transition to Podocyrtis ampla defines the base of the Podocyrtis ampla Zone.

PHYLOGENY

There is little doubt that P. (P.) phyxis is descended from P. (P.) diamesa, and it seems likely that P. (P.) ampla is its descendant.

REMARKS

For generic level taxonomy see Sanfilippo and Riedel, 1992.

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