Taxonomy, morphology and phylogeny of Late Cretaceous spirulid coleoids (Cephalopoda) from Greenland and Canada

Abstract

: Groenlandibelus rosenkrantzi from the Maastrichtian of Greenland has long been thought to constitute an early representative of spirulid coleoids. This study shows that this view must be reassessed, at least in part. A re‐investigation of the types and of material recorded subsequently has revealed that none of these specimens is conspecific with the holotype of G. rosenkrantzi. Cyrtobelus birkelundae gen. nov, sp. nov. differs from the type of G. rosenkrantzi in having lower chambers and in lacking an apically elongated sheath. The longiconic phragmocone of G. rosenkrantzi has more features in common with the presumed spirulid genus Naefia. A specimen described in detail by J. A. Jeletzky in the mid 1960s as ‘G. rosenkrantzi’ is designated holotype of C. birkelundae sp. nov., which means that internal phragmocone features are still unknown in G. rosenkrantzi. Cyrtobelus hornbyense gen. nov, sp. nov. from the Campanian of western Canada constitutes the first record of early spirulids from the northeast Pacific, being based on seventeen extraordinarily well‐preserved phragmocones. This species differs from C. birkelundae sp. nov. only in the width of the siphuncular tube. The presence of a caecum, a nacre‐less conotheca that represents the continuation of the protoconch conotheca, conothecal flaps that anchor the mural parts of the septa, and a thin investment‐like sheath are characters shared only with Recent Spirula. In particular, the unusual protoconch architecture of Cyrtobelus gen. nov. challenges a phylogenetic origin within bactritoid‐like coleoids.

Buoyancy mechanisms limit preservation of coleoid cephalopod soft tissues in Mesozoic Lagerstätten

“…Spirula spirula ) (Fuchs et al . , ) have been found in other Cretaceous sediments. Recent work has proposed that teuthids diverged from a belemnoid ancestor ( Longibelus gen. nov.) during the Early Cretaceous (Fuchs et al .…”

Diversity, morphology, and phylogeny of coleoid cephalopods from the Upper Cretaceous Plattenkalks of Lebanon-Part I: Prototeuthidina

“…Shell remains of the following Late Cretaceous coleoid genera other than Belemnoidea and Octobrachia have been described previously; Naefia Wetzel, 1930, from the Maastrichtian of Chile (Wetzel 1930) and possibly from the Campanian of Antarctica (Wetzel 1930;Stilwell and Zinsmeister 1987) and California (Hewitt et al 1991);Cyrtobelus Fuchs, Keupp, Trask, and Tanabe, 2012, from the upper Campanian to the upper Maastrichtian of Vancouver Island, British Columbia, Canada, and West Greenland (Fuchs et al 2012);Groenlandibelus Jeletzky, 1966, from the upper Maastrichtian of Greenland (Birkelund 1956;Fuchs et al 2012Fuchs et al , 2013aand Longibelus Fuchs, Iba, Ifrim, Nishimura, Kennedy, Keupp, Stinnesbeck, and Tanabe, 2013 from the Aptian of the Caucasus (Doguzhaeva 1996), the Albian of South Africa and southern India, and the Cenomanian-Maastrichtian of Japan (Hirano et al 1991;Hewitt et al 1991;Fuchs and Tanabe 2010), southern India (Doyle 1986), Mexico (Ifrim et al 2004), and Alaska. Among these genera, the former three were included in either the order Sepiida (Jeletzky 1966) or the order Spirulida (Fuchs et al 2012(Fuchs et al , 2013a, while Longibelus was assumed to be a taxon linking the Belemnoidea and the early Decabrachia (Fuchs et al 2013a). Although jaws and a complete proostracum are unknown, all these genera are represented by small phragmocones, usually less than 10 cm in length, suggesting their smaller body size than Haboroteuthis.…”

Longibelus gen. nov., a new Cretaceous coleoid genus linking Belemnoidea and early Decabrachia

“…Diplobelida are belemnoid‐like in having a narrow stripe‐like attachment scar and in the absence of a caecum (Fuchs et al . 2012 a ). On the other side, diplobelids and early spirulids share a submarginal siphuncle and the absence of a rostrum proper.…”

“…Because diplobelids have a submarginal siphuncle (Jeletzky , Fuchs et al . 2012 a ), two ways of character polarization are possible: (1) Longibelus gen. nov. is closer to the Belemnitida: a submarginal siphuncle is then autapomorphic for a group including Diplobelida and all subgroups of the Decabrachia. (2) Longibelus gen. nov. is closer to the Spirulida: in this case, the siphuncle of both diplobelids and spirulids migrated independently towards dorsal as a result of similar requirements to their life style and therefore is apomorphic for the Diplobelida and Spirulida (Fig.…”