Cephalopod origin and evolution: A congruent picture emerging from fossils, development and molecules

Abstract

Cephalopods are extraordinary molluscs equipped with vertebrate-like intelligence and a unique buoyancy system for locomotion. A growing body of evidence from the fossil record, embryology and Bayesian molecular divergence estimations provides a comprehensive picture of their origins and evolution. Cephalopods evolved during the Cambrian (∼530 Ma) from a monoplacophoran-like mollusc in which the conical, external shell was modified into a chambered buoyancy apparatus. During the mid-Palaeozoic (∼416 Ma) cephalopods diverged into nautiloids and the presently dominant coleoids. Coleoids (i.e. squids, cuttlefish and octopods) internalised their shells and, in the late Palaeozoic (∼276 Ma), diverged into Vampyropoda and the Decabrachia. This shell internalisation appears to be a unique evolutionary event. In contrast, the loss of a mineralised shell has occurred several times in distinct coleoid lineages. The general tendency of shell reduction reflects a trend towards active modes of life and much more complex behaviour.

Biogeografia historica de los calamares de la familia Loliginidae (Teuthoidea: Myopsida)

“…La información para calibrar el reloj molecular, considerando al grupo interno y externo fue: i) en la raíz, los precursores de los espirúlidos, de hace 119 Ma (Young et al, 1998;Kröger et al, 2011); ii) en el ingroup, Loliginidae según Clarke & Maddock (1988) y Clarke (2003), con origen en la base del Eoceno (58 Ma); y iii) el origen de Loligo, mediante estatolitos del Eoceno medio, hace unos 44 Ma (Clarke & Fitch, 1979). Las calibraciones se realizaron bajo una distribución tipo normal, con data fósil asociada al valor medio de la distribución.…”

Wrinkle layer and supracephalic attachment area: implications for ammonoid paleobiology

“…Tentacles and arms are stacked together to improve streamlining. Ten arms in both ammonites are shown because Nautilus and representatives of Coleoidea exhibit five arm pairs during early embryonic development, there can be an initial number of arms in Cephalopoda (Shigeno et al 2008, Kröger et al 2011. Two long tentacles are very speculative and based on reconstructions in Westermann (1996, fig.…”

“…However, ten arms (five pairs) represent the plesiomorphic state in the Cephalopoda , Shigeno et al 2008. It is known that Ammonoidea (Kröger et al 2011). Coleoids have ten arms and they branched off from their ancestors later than ammonoids did.…”

First report of Devonian bactritids (Cephalopoda) from South America: paleobiogeographic and biostratigraphic implications

“…In addition to the interesting phylogenetic aspects concerning their origin, their important role in the evolutionary history of cephalopods has been especially debated (e.g., Erben, 1964;Kröger and Mapes, 2007;Kröger et al, 2011;Klug et al, 2015). The present consensus assumes they evolved from an orthocerid group during the latest SilurianEarly Devonian, and, in turn, gave rise to ammonoids during the Devonian and to coleoids in the Mississippian (Erben, 1966;Mapes, 1979;Doguzhaeva, 2002;Kröger and Mapes, 2007;Klug et al, 2015).…”