Praeactinocamax cf. strehlensis (Fritsch, 1872)
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publication ID |
https://doi.org/ 10.4202/app.2009.0065 |
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persistent identifier |
https://treatment.plazi.org/id/038187E9-0761-FFFB-FCFA-FF72FB00FA33 |
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treatment provided by |
Felipe |
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scientific name |
Praeactinocamax cf. strehlensis |
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Praeactinocamax cf. strehlensis (Fritsch, in Fritsch and Schloenbach, 1872)
Fig. 4F View Fig
Material.—IGP_Upo2009/8, a single incomplete specimen comprising an alveolar part of a rostrum.
Description.—The preserved alveolar part is 17.3 mm long. The cross−section is heart−shaped to triangular. The pseudoalveolus (depth 7.2 mm) and the ventral notch (length: 6 mm) are well developed. The lateral sides are slightly concave, which suggests that the entire rostrum had a lanceolate shape. The surface of the rostrum is partly granulated, and striation is visible in the vicinity of the ventral notch.
Discussion.—The figures by Fritsch of the lectotype and paralectotype (Fritsch and Schloenbach 1872: pl. 16: 10–12) show a lanceolate rostrum with a well developed ventral notch. The character of the anterior part (including the pseudoalveolus) is almost identical with our specimen. From Fritsch's drawing, it is not possible to determine the depth of the pseudoalveolus, which was probably infilled by sediment. Due to the good accordance with the figure of the lectotype of P. strehlensis , we are inclined to assign our alveolar fragment to this species, albeit in open nomenclature since the rostrum is incomplete. In the presence of granulation, the estimated size of the rostrum and the cross−section of the alveolar end, our specimen shows considerable similarities with P. bohemicus . However, our fragment clearly differs from P. bohemicus (and other European representatives of the genus, e.g., P. primus , P. plenus ) in the occurrence of a pseudoalveolus instead of a small pit. The progressive calcification of the aragonitic posterior part of the rostrum (see Košťák and Wiese 2008 for discussion and photographic documentation), as observed in terminal Turonian and early Coniacian Praeactinocamax and in the Goniocamax – Belemnitella lineage ( Ernst 1964; Christensen 1997a; Christensen and Schulz 1997), leads to the development of the pseudoalveolus. Thus, the occurrence of a pseudoalveolus in conjunction with the considerable morphological similarity to P. bohemicus suggests that P. strehlensis may represent an early anagenetic transition from P. bohemicus .
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