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Genus Castellanibelus Combémorel, 1973
Castellanibelus? bonti sp. nov.
Holotype – RGM 361 611 (monotypic), section E (bed E86) in the Tornajo Mountain, earliest late Valanginian (Verrucosum Zone).
Derivatio nominis – Named after Willem Bont of Amsterdam (Dutch ammonite collector).
Diagnosis – Medium sized rostrum, dorso-ventrally depressed, with prominent alveolar groove. Marked lateral extensions give way to a leaf-like outline in dorsal view. In lateral view the dorsal side is flattened, while the ventral side is curved. The apex is mucronate (typical in Castellanibelus). The alveolus is very shallow.
Description – Strongly dorso-ventrally depressed rostrum with a prominent dorsal groove that extends almost from the alveolus to the apex (in Fig. 1, partially obscured by an attached bivalve (in apical part) and by some lithified calcareous rock (in anti-apical part)). The apex is slightly weathered, but a mucron is present. The cross-section of the alveolar region is quadrangular with clear lateral extensions due to the well-developed lateral sides. In lateral view, the dorsal side is almost straight and, except for the apical region, appears to stay throughout the alveolar region (as far as it is preserved). The ventral side is strongly curved. The alveolus is shallow and penetrates approximately 5 mm into the rostrum.
Remarks – The drop-like shape, in dorsal or ventral view, is atypical for the genus Castellanibelus, as is the strongly expanded lateral area. The latter is atypical for any known belemnite genus or species. The duvaloid-aspect, combined with the strongly depressed rostrum, at least points to a close relation with the genus Castellanibelus.