Cretaceous spirulids

Introduction

While Cenozoic representatives of the Spirulida are well-known since the 19^th century, Cretaceous ancestors of Spirula are first evident since Jeletzky (1966). Owing to a Spirula-like caecum that enters the lumen of the protoconch of a Late Cretaceous orthoconic phragmocone with conspicuously long chambers and without a belemnite-like rostrum, Jeletzky (1966) established the family Groenlandibelidae. Today, four species in three genera can reliably be placed within this spirulid family (Fuchs et al. 2012). Groenlandibelidae differ from belemnoids by the presence of a caecum, a narrow rod-like proostracum, wide soft tissue attachment scars, and the absence of a solid rostrum and tabular nacre in the shell wall (Fuchs et al. 2012). In contrast to Cenozoic spirulids (e.g. Beloptera, Spirulirostra), groenlandibelid phragmocones are not yet coiled.

The origin of groenlandibelids is still enigmatic. Morphologically, Cenomanian-Maastrichtian Longibelus matsumotoi and Aptian Longibelus kabanovi appear to be intermediate between belemnoid diplobelids and groenlandibelids (Fuchs & Tanabe 2010, Fuchs et al., 2013).

Soft tissues are unknown from the fossil record (except soft tissue attachment scars on the inside of each chamber ).

Classification

• Groenlandibelidae Jeletzky, 1966
  
• Groenlandibelus Jeletzky, 1966
  
• Groenlandibelus rosenkrantzi (Birkelund, 1956) (Maastrichtian of Greenland)
  
• Naefia Wetzel, 1930
  
• Naefia neogaeia Wetzel, 1930 (Maastrichtian of Chile)
  
• Cyrtobelus Fuchs et al., 2012
  
• Cyrtobelus birkelundae Fuchs et al., 2012 (Maastrichtian of Greenland)
• Cyrtobelus hornbyense Fuchs et al., 2012 (Campanian of Canada)
  
• Family and order uncertain
  
• Longibelus Fuchs et al., 2013
  
• Longibelus matsumotoi (Hirano et al., 1991) (Cenomanian-Maastrichtian of Japan)
• Longibelus cf. matsumotoi (Albian of southern India and South Africa, Maastrichtian of Alaska, Chile, Mexico,
  
• Longibelus kabanovi (Doguzhaeva, 1996) (Aptian of Caucasus)

References

Fuchs, D., Iba, Y., Ifrim, Ch.; Nishimura, T., Kennedy, J., Keupp, H., Stinnesbeck, W. and Tanabe, K. 2013. Longibelus n. gen. a new Cretaceous coleoid genus linking Belemnoidea and early Decabrachia. Palaeontology, 56 (5): 1081-1106. DOI:10.1111/pala.12036

Fuchs, D., Keupp, H., Trask, P. and Tanabe, K. 2012. Taxonomy, morphology and phylogeny of Late Cretaceous spirulid coleoids (Cephalopoda) from Greenland and Canada. Palaeontology, 55 (2): 285-303. DOI: 10.1111/j.1475-4983.2011.01125.x

Fuchs, D. and Tanabe, K. 2010. Re-investigation of the shell morphology and ultrastructure of the late Cretaceous spirulid coleoid Naefia matsumotoi. In: Proceedings of the 7th International Symposium - Cephalopods - Present & Past, Sapporo. 195-207.

Jeletzky, J. A. 1966. Comparative morphology, phylogeny and classification of fossil Coleoidea. Paleontological Contributions, University of Kansas, Mollusca, 7, 1–166.