The locomotion system of Mesozoic Coleoidea (Cephalopoda) and its phylogenetic significance

Abstract

A morphological comparison of shell‐muscle contacts in coleoid cephalopods mainly from the Early Jurassic (Toarcian) Posidonia Shales of Holzmaden (Germany), the Middle Jurassic (Callovian) Oxford Clay of Christian Malford (UK), Late Jurassic (Kimmeridgian‐Tithonian) plattenkalks of Solnhofen (Germany), and the Late Cretaceous (Cenomanian) of Hâdjoula and Hâkel (Lebanon) provides new and meaningful insights into their locomotion systems. The study shows that both pro‐ostracum‐ and gladius‐bearing coleoids are typified by a marginal mantle attachment and by distinctly separated fins, which usually insert (indirectly via the shell sac and basal fin cartilages) to posterior shell parts. While absent in gladius‐bearing forms, mantle‐locking cartilages might have existed already in pro‐ostracum‐bearing belemnoids. Similar to ectocochleate ancestors, funnel‐ and cephalic retractors are generally attached to the internal (ventral) shell surface. A comparison of Mesozoic and Recent gladius‐bearing coleoids shows that the locomotion system (most significantly the dorsal mantle configuration, and the presence of nuchal‐ and funnel‐locking cartilages) is fundamentally different. This does not support the concept of ‘fossil teuthids’, but suggests, owing to similarities with Recent Vampyroteuthis, placement of Mesozoic gladius‐bearing coleoids within the Octobrachia (Octopoda + Vampyromorpha). Classification of Mesozoic gladius‐bearing coleoids as octobrachians implies that: (1) unambiguous teuthids are still unknown in the fossil record and (2) the similarity between Recent and some fossil gladiuses represents a matter of homoplasy.

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

“…The mass reclassification of fossil teuthids in the Vampyropoda has been termed the ‘Vampyropoda hypothesis’ and indicates a complete absence of decabrachian teuthid coleoids in the fossil record (Fuchs & Larson ; Fuchs et al . ). The most recent phylogenetic work using both extant and fossil data corroborates the Vampyropoda hypothesis (Sutton et al .…”

Diversity and morphological evolution of Jurassic belemnites from South Germany

“…1), which are especially abundant in marine sediments of the Jurassic and Cretaceous. These organisms, considered as stem-group decabranchian coleoids Fuchs et al, 2015;Klug et al, 2016) (Fig. 1), composed a large part of the Mesozoic nekton and held a key position in the dynamics of trophic webs (i.e., as predators of small organisms and preys for marine reptiles and chondrichthyans; Massare, 1987;Doyle and MacDonald, 1993;Martill et al, 1994;Walker and Brett, 2002).…”

Rostrum size differences between Toarcian belemnite battlefields

“…However, the evolutionary and ecological importance of the Lilliput effect remains poorly understood. Furthermore, because of physiological differences, not all organisms necessarily exhibit a body size reduction in the face of warming or other environmental stresses (Gardner et al, 2011;Ohlberger, 2013). Some authors even consider that, in some cases, the body size reduction might reflect a preservation or collection artefact (McGowan et al, 2009;Brayard et al, 2010).…”