Podocyrtis (Podocyrtis) papalis Ehrenberg

Podocyrtis papalis Ehrenberg, 1847b, p.55, fig.2; Riedel and Sanfilippo, 1970, p.533, pl.11, fig.1; Sanfilippo and Riedel, 1973, p.531, pl.20, figs.11-14, pl.36, figs.2-3

DESCRIPTION

Cephalis subhemispherical, with many small pores, bearing a horn of variable length, which is usually three-bladed, sometimes conical. Collar stricture marked by change in contour. Thorax inflated-conical, with circular pores in longitudinal rows separated by ribs. Lumbar stricture not (or only very slightly) expressed externally. Abdomen inverted truncate-conical, with pores and ribs similar to those of thorax. Pored part of abdomen generally shorter than thorax, and this is followed by a poreless part of the abdominal wall from which arise three large, shovel-shaped feet (Riedel and Sanfilippo, 1970).

DIMENSIONS

Length (excluding horn) 170 (rarely 150) to 280 m maximum breadth 95-140 m (Riedel and Sanfilippo, 1970).

DISTINGUISHING CHARACTERS

P. papalis is distinguished from P. (Podocyrtoges) diamesa by being smaller, and spindle-shaped, without an external change in contour at the lumbar stricture. The cephalis is more distinctly three-lobed than in members belonging to the ancestral genus Cryptocarpium, from which P. papalis also differs by having longitudinal costae between rows of pores on the thorax and the abdomen. It is distinguished from the earliest member of the Lampterium subgenus, P. (Lampterium) acalles, by the shell being widest just above the lumbar stricture, whereas P. (L.) acalles is widest just below the lumbar stricture. Three shovel-shaped feet are always present, except in the earliest form where the abdomen terminates in a broad poreless zone (Sanfilippo, unpubl. data).

VARIABILITY

Early forms are smaller, the cephalis is approximately uniformly perforated by pores, bearing a short, broad-based three-bladed horn. In these early forms the unpaired lobe is only slightly longer than the paired lobes. The earliest specimens have ridges separating longitudinal rows of pores and no feet, but terminate in a broad, poreless zone. In later forms the unpaired lobe is approximately twice as long as the paired lobes, poreless or with a few scattered pores, bearing a horn of variable length that is usually three-bladed, sometimes conical (Sanfilippo, unpubl. data).

DISTRIBUTION

P. papalis is a prominent constituent of Eocene assemblages from paleolatitudes lower than 45. The morphotypic first appearance of this species lies within early part of the Bekoma bidartensis Zone and its morphotypic last appearance is approximately synchronous with the lower limit of the Cryptocarpium ornatum Zone.

PHYLOGENY

P. papalis developed from Cryptocarpium in the late Paleocene B. bidartensis Zone and gave rise to the subgenera Lampterium, Podocyrtoges and Podocyrtopsis.

REMARKS

For generic level taxonomy see Sanfilippo and Riedel, 1992.

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