Belemnitella praecursor Stolley sensu lato w kampanie dolnym okolic Sulejowa nad Wisłą

Michał Jamiołkowski

Abstrakt


BELEMNITELLA PRAECURSOR STOLLEY SENSU LATO IN THE LOWER CAMPAN IN THE VICINITY OF SULEJÓW ON THE VISTULA RIVER

Summary
The paper deals with specimen of the Belemnitella praecursor Stoll. var. mucronatiformis Jeletz. found in layers being referred by W. Pożaryski (1938, 1948) to the lower Campanian (level "i").
That is confirmed by co-occurrence Gonioteuthis quadrata Blv. and Inoceramus lingua Boehm. These specimens were found together at the same place, situated in the scarp of the Vistula valley south of Sulejów. Bellow the author describes some important taxonomical features of the specimen investigated. (Figs. l, 2, 3).
Rostrum elongate. From the ventral view slightly lanceolate, by weak lateral flattening of the alveolar part. From the lateral view the rostrum is cone-shaped. In the well-preserved specimens the depth of alveolus reaches probably one third of the length.
The alveolar angle amounts 21°. The bottom of ventral fissure forms an arch bent to the back of the rostrum. With the alveolar wall it forms an angle amounting 52°.
Szatsky's Index is 7 mm, Nowak's Index 8,5 mm (it means a distance of the outer exit of bottom of the ventral fissure from the protoconch, which is measured on the rostrum axion. This index has been introduced by prof. R. Kongiel - the paper in print). Ventral fissure is long about one second of the depth of alveolus. The cross-section of alveolus is oval. Ornamentation of the rostrum is not quite rich, however, it has characteristic features of the genus Belemnitella. Double dorso-lateral furrows, longitudinal depression and lateral single furrow, are distinct. Vascular impressions are visible only at the ventral side, especially around the ventral fissure.
When comparing with representatives of this species described by: E. Stolley (1897), G. Muller, A. Wollemann (1906), A. D. Arkhangielski (1912), J. A. Jeletzky (1951, 1955), Schmid (1956), the specimen found may be referred to the subspecies Belemnitella praecursor Stol1. var. mucronatiformis Jeletz.

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