Fusiteuthis, 1962

Christensen, Walter Kegel, 2002, Fusiteuthis polonica, a rare and unusual belemnite from the Maastrichtian, Acta Palaeontologica Polonica 47 (4), pp. 679-683 : 681-682

Affinities of Fusiteuthis

Kongiel (1962: p. 28) noted that Fusiteuthis “is nearest to the genus Actinocamax but differs in its well developed alveolus (eualveolus with preserved conotheca) and the lack of dorso−lateral double furrows, also in complete lack of ornamentation”.

Naidin (1964) erected two new subgenera of Actinocamax : A. ( Praeactinocamax ), type species Belemnites plenus Blainville , and A. ( Paractinocamax ), type species Actinocamax grossouvrei Janet , in addition to the nominotypical subgenus. Moreover, he established one new genus, Belemnellocamax , type species Belemnites mammillatus Nilsson. A. ( Paractinocamax ) was placed in synonymy with Belemnellocamax by Christensen (1986) and A. ( Praeactinocamax ) was elevated to full generic rank by Christensen (1997). Species placed in Belemnellocamax were assigned to Actinocamax before 1964.

With respect to the size and shape of the guard the holotype of F. polonica somewhat resembles some species of Praeactinocamax , e.g., adolescent specimens of the Cenomanian P. plenus (see Christensen 1974), and the Santonian Belemnellocamax toucasi (Janet) , but it differs in the structure of the alveolar end. Praeactinocamax generally has a low cone−shaped alveolar fracture anteriorly, or more rarely a very shallow pseudoalveolus, and B. toucasi has a very shallow pseudoalveolus, in contrast to Fusiteuthis which has a shallow alveolus.

With regard to the shape of the guard MGUH 26406 is somewhat similar to juvenile specimens of the Cenomanian Praeactinocamax primus (Arkhangelsky) (see Christensen 1990) and P. plenus (see Christensen 1974), but, again, it differs in possessing a shallow alveolus rather than a shallow pseudoalveolus. Moreover, the maximum lateral diameter is situated in the middle part of the guard in MGUH 26406, and generally in the lower third in the two species of Praeactinocamax .

MGUH 26406 is also somewhat similar to juvenile specimens of the uppermost Lower Campanian Belemnellocamax mammillatus and the lowermost Upper Campanian B. balsvikensis (Brotzen) (cf. Christensen and Schulz 1976, Figs. 1A–E ), but it differs in possessing a shallow alveolus rather than a shallow pseudoalveolus and more lanceolate shape of the guard in ventral view.

According to Schulz (1979, 1982) the upper half of the Belemnella lanceolata Zone of the “Saturn” pit has yielded Belemnella lanceolata (Schlotheim) , Belemnella inflata (Arkhangelsky) , and Belemnitella pulchra Schulz. B. pulchra differs from F. polonica in its deeper alveolus, stouter guard and conspicuous vascular markings, among other characters. Juvenile specimens of B. lanceolata and B. inflata are very slender and have weakly developed or no vascular markings. MGUH 26406 differs from these in its markedly more shallow alveolus.

Figures

Fig. 1. Dots show the geographical occurrences of the Maastrichtian belemnitellid genus Fusiteuthis Kongiel.