Olcostephanus Neumayr, 1875

Vašíček, Zdeněk, Błażejowski, Błażej, Gaździcki, Andrzej, Król, Maria, Lefeld, Jerzy, Skupien, Petr & Wierzbowski, Andrzej, 2020, Early Cretaceous ammonites and dinoflagellates from the Western Tatra Mountains, Poland, Acta Palaeontologica Polonica 65 (4), pp. 799-810 : 802

Genus Olcostephanus Neumayr, 1875

Type species: Ammonites astierianus d’Orbigny, 1840 ; Castellane, France, Lower Hauterivian, by original designation .

Olcostephanus densicostatus ( Wegner, 1909) Fig. 3G .

1909 Astieria atherstoni var. densicostata n. v.; Wegner 1909: 82, pl. 16: 3.

1974 Olcostephanus astierianus (d’Orb.) ; Lefeld 1974: 350, pl. 10: 3,?4.

2005 Olcostephanus densicostatus (Wegner) ; Klein 2005: 84 (cum syn.).

2010 Olcostephanus densicostatus (Wegner) ; Vašíček 2010: 398, pl. 2: 1.

Material.—A single, strongly flattened, relatively imperfect outer mould ( ZPAL Am. 25/4b), preserved partially as an imprint, primarily positive, from Cretaceous, Tatra Mountains, Poland.

Description.—Involute specimen with high whorls. Dmax about 75 mm (affected by deformation). The sculpture is formed by thin and dense ribs slightly inclined to the aperture. Venter ribs run across without interruption, very strongly arched toward the aperture over a short section. With a few exceptions, the ribs do not bifurcate. Only on the imprint, deep, probably short and longitudinally elongated depressions after strong umbilical tubercles, which correspond to primary ribs, appear near the umbilicus. About 4–5 ribs run out of the tubercles; other ribs, approximately in the same number, are connected to the area between the primary ribs.

Remarks.—Imperfectly preserved outer mould bears dense, thin ribs which are not bifurcated on flanks of the whorl. A similar finding designated as Olcostephanus astierianus is mentioned by Lefeld (1974: pl. 10: 3) and Grabowska­Hakenberg (1958) from Lower Cretaceous marl in the Kościeliska Valley in the Polish part of the Tatra Mountains).

Stratigraphic and geographic range.—According to Reboulet (1996), Olcostephanus densicostatus occurs from the upper part of Upper Valanginian (the uppermost part of Neocomites peregrinus Zone ) to the base of Crioceratites loryi Ammonite Zone (Lower Hauterivian). The species has a very broad geographical distribution. Among others, according to Vašíček (2010) it occurs also in the uppermost Valanginian of the Mráznica Formation in the Butkov Quarry ( Slovakia).

Figures

Fig. 3. The Lower Cretaceous ammonites from the Kościeliska Marl Formation in the Lejowa Valley, Tatra Mountains, Poland. A, C–E. Criosarasinella cf. subheterocostata Reboulet, 1996. A. ZPAL Am. 25/19. C. ZPAL Am. 25/7. D. ZPAL Am. 25/17. E. ZPAL Am. 25/14. B. Calcite valve of aptychus Didayilamellaptychus seranonis (Coquand, 1841), ZPAL Am. 25/12. F. Spitidiscus cf. cankovi Vašíček and Michalík, 1986, ZPAL Am. 25/9. G. Olcostephanus densicostatus (Wegner, 1909), ZPAL Am. 25/4.All in lateral view.