Belemnitellidae Pavlow, 1914
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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/038187E9-0763-FFFB-FCFA-F9FEFDF0F805 |
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treatment provided by |
Felipe |
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scientific name |
Belemnitellidae Pavlow, 1914 |
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Family Belemnitellidae Pavlow, 1914 View in CoL Genus Praeactinocamax Naidin, 1964 Praeactinocamax bohemicus ( Stolley, 1916)
Fig. 4A–E View Fig .
Holotype: Specimen No. NM−O3217, stored in the National Museum in Prague, formerly described and figured as Belemnites strehlensis by Fritsch,in Fritsch and Schloenbach, 1872 (Fritsch and Schloenbach 1872: 19, pl. 16: 17). Designated later as Actinocamax bohemicus by Stolley (1916), for details see Christensen (1982) and Košťák et al. (2004).
Type locality and horizon: The Teplitzer Schichten (now Teplice Formation) at Koštice near Louny, in the Bohemian Cretaceous Basin, Czech Republic.
Remarks.—For a comprehensive synonymy see Stolley (1916), Christensen (1982), and Košťák (1996).
Material.—Two complete rostra and four fragments from the Upper Turonian of the Úpohlavy working quarry, IGP_Upo 2009/1−6. An additional fragment [PG Uy2002/1 (CIGP) registered now as IGP_Upo2009/7] was used for stable isotope analysis by Wiese et al. (2004; see Fig. 2) and is largely destroyed.
Description.—The complete rostra (IGP_Upo2009/1, 2) are of medium to small size, not exceeding 65 mm in length. The shape is highly conical in lateral view and cylindrical to subcylindrical in dorsoventral view ( Fig. 4A–D View Fig ). The alveolar end is low−conical ( Fig. 4C–E View Fig ; specimens IGP_Upo2009/1, 2, 4) to flat (specimen IGP_Upo2009/3; Fig. 4B 4 View Fig ), with a shallow pit in the centre. The cross−section is oval ( Fig. 4C 4 View Fig , E 2) to triangular ( Fig. 4B 4, D 4 View Fig ), with concentric and radial structures present ( Fig. 4B 4, C 4, D 4, E 4 View Fig ). Three marked concentric ribs were observed in the dorsal part of the alveolar end of all specimens (clearly visible in Fig. 4C 4, D 4 View Fig ). The ventral furrow is well developed (not exceeding 3mm), with striation in the vicinity ( Fig. 4B–E View Fig ). Due to the exceptional preservation, new morphological features of the species were recognised. Granulation is observed over the entire surface of the rostrum, with coarser granules concentrating close to the alveolar end (= alveolar fracture, specimen IGP_Upo2009/2, Fig. 4C View Fig 1 –C View Fig 3 View Fig ). Additionally, striation occurs on the ventral side of the rostrum. Faint dorsolateral furrows were observed in specimens IGP_Upo2009/1, 2, 5; Fig. 4A View Fig 1 View Fig , C 3 View Fig , D 2). Dorsolateral furrows have not previously been observed in this species, except in the case of the incomplete specimen from Särdal ( Sweden) which probably belongs to P. bohemicus ( Christensen 1982; Košťák et al. 2004). The double furrows in the Úpohlavy specimens are more readily felt than actually seen and are mostly invisible in less well preserved specimens.
Discussion.— Praeactinocamax bohemicus is a distinct species, which shows the greatest morphological similarities with the Middle Turonian P. manitobensis / walkeri / sternbergi group of the NAP ( Košťák et al. 2004). “ Actinocamax sp. aff. strehlensis “ (Fritsch and Schloenbach, 1872) described by Jeletzky (1950: 12–17, text−fig. 2, pl. 3: 4, 5) from Manitoba, Canada, shows close similarities with P. bohemicus and may be conspecific.
Stratigraphic and geographic range.—Late Turonian Subprionocyclus neptuni and Prionocyclus germari zones. Czech Republic, Germany, Sweden (see also Košťák et al. 2004).
Praeactinocamax strehlensis (Fritsch, in Fritsch and Schloenbach, 1872)
Type material: The lectotype (Fritsch and Schloenbach 1872: 19, pl. 16: 10) and the (implied) paralectotype (Fritsch and Schloenbach 1872: 19, pl. 16: 11, 12) designated by Birkelund (1956) and housed originally in the Dresden Museum, are believed to be lost.
Type locality and horizon: The Strehlen Limestone, Strehlen, Saxony.
Remarks.—For a comprehensive synonymy see Christensen (1982).
Stratigraphic and geographic range.— Late Subprionocyclus neptuni Ammonite Zone , late Turonian, Late Cretaceous. Strehlen Limestone ( Germany) and Hudcov Limestone ( Czech Republic). Both limestone units are stratigraphic equivalents of the upper part of the Hyphantoceras Event.
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