Evolution of cephalopods

The cephalopods have a long geological history, with the first nautiloids found in late Cambrian strata.[1]

The class developed during the middle Cambrian, and underwent pulses of diversification during the Ordovician period[2] to become diverse and dominant in the Paleozoic and Mesozoic seas. Small shelly fossils such as Tommotia were once interpreted as early cephalopods, but today these tiny fossils are recognized as sclerites of larger animals,[3] and the earliest accepted cephalopods date to the Middle Cambrian Period. During the Cambrian, cephalopods are most common in shallow near-shore environments, but they have been found in deeper waters too.[4] Cephalopods were thought to have "undoubtedly" arisen from within the tryblidiid monoplacophoran clade.[5] However genetic studies suggest that they are more basal, forming a sister group to the Scaphopoda but otherwise basal to all other major mollusc classes.[6][7] The internal phylogeny of Mollusca, however, is wide open to interpretation – see mollusc phylogeny.

  1. ^ Dzik, J. (1981). "Origin of the cephalopoda" (PDF). Acta Palaeontologica Toe. 26 (2): 161–191.
  2. ^ Kröger, B.; Yun-bai, Y. B. (2009). "Pulsed cephalopod diversification during the Ordovician". Palaeogeography, Palaeoclimatology, Palaeoecology. 273 (3–4): 174–201. Bibcode:2009PPP...273..174K. doi:10.1016/j.palaeo.2008.12.015.
  3. ^ Begtson, Stefan (1970). "The Lower Cambrian fossil Tommotia". Lethaia. 3 (4): 363–392. Bibcode:1970Letha...3..363B. doi:10.1111/j.1502-3931.1970.tb00829.x.
  4. ^ Landing, Ed; Kröger, Björn (2009). "The Oldest Cephalopods from East Laurentia". Journal of Paleontology. 83 (1): 123–127. Bibcode:2009JPal...83..123L. doi:10.1666/08-078R.1. S2CID 128877531.
  5. ^ Clarke, M.R.; Trueman, E.R., eds. (1988). "Main features of cephalopod evolution". The Mollusca. Vol. 12: Palaeontology and Neontology of Cephalopods. Orlando, Fla.: Acad. Pr. ISBN 978-0-12-751412-3.
  6. ^ Giribet, G.; Okusu, A, A.; Lindgren, A.R., A. R.; Huff, S.W., S. W.; Schrödl, M, M.; Nishiguchi, M.K., M. K. (May 2006). "Evidence for a clade composed of molluscs with serially repeated structures: monoplacophorans are related to chitons". Proceedings of the National Academy of Sciences of the United States of America. 103 (20): 7723–7728. Bibcode:2006PNAS..103.7723G. doi:10.1073/pnas.0602578103. PMC 1472512. PMID 16675549.
  7. ^ Sumner-Rooney, Lauren H.; Schrödl, Michael; Lodde-Bensch, Eva; Lindberg, David R.; Heß, Martin; Brennan, Gerard P.; Sigwart, Julia D. (2015). "A neurophylogenetic approach provides new insight to the evolution of Scaphopoda: A neurophylogenetic approach in Scaphopoda". Evolution & Development. 17 (6): 337–346. doi:10.1111/ede.12164. PMID 26487042. S2CID 37343813.