145576 20260217205604.0 doi 10.1146/annurev-earth-031621-113343 sideral 140384 ART-2024-140384 eng Rahman, Imran A. Origin and Early Evolution of Echinoderms 2024 Access copy available to the general public Unrestricted Echinoderms are a major group (phylum) of invertebrate animals with a rich fossil record stretching back to the Cambrian period, approximately 518 million years ago. While all modern species are characterized by pentaradial (i.e., fivefold) symmetry, Cambrian echinoderms also include taxa with different types of symmetry (e.g., bilateral symmetry). These distinct forms were present from very early in the phylum's history, demonstrating that the initial diversification of echinoderm body plans was extremely rapid. The phylogenetic relationships of Cambrian echinoderms have long been debated, hindering efforts to reconstruct the evolution of the phylum, but recent analyses have consistently recovered bilaterally symmetrical forms as the earliest-diverging echinoderms. This reveals the sequence of character acquisition in echinoderm evolution, indicating that radial symmetry is a derived character of the group, which evolved after the acquisition of a mineralized skeleton. Cambrian echinoderms were adapted to diverse modes of life, with ecology an important factor shaping their early evolution. However, the reasons why echinoderms evolved their unique pentaradial body plan remain unclear. ▪The Cambrian fossil record provides valuable insights into the origin and early evolution of echinoderms over half a billion years ago.▪Cambrian echinoderms were morphologically diverse, with several extinct groups exhibiting character combinations that distinguish them from living species.▪Phylogenetic analyses of bilateral, asymmetrical, triradial, and pentaradial fossils have allowed us to decipher the assembly of the modern echinoderm body plan.▪Echinoderms became ecologically diverse early in their history, with varied modes of feeding, locomotion, and attachment. info:eu-repo/grantAgreement/ES/DGA/E18-17R info:eu-repo/grantAgreement/ES/MICINN/PID2021-125585NB-I00 info:eu-repo/semantics/openAccess by https://creativecommons.org/licenses/by/4.0/deed.es 13.0 2024 GEOSCIENCES, MULTIDISCIPLINARY 3 / 258 = 0.012 2024 Q1 T1 ASTRONOMY & ASTROPHYSICS 6 / 84 = 0.071 2024 Q1 T1 5.885 2024 Astronomy and Astrophysics 2024 Q1 Space and Planetary Science 2024 Q1 Earth and Planetary Sciences (miscellaneous) 2024 Q1 26.1 2024 info:eu-repo/semantics/article info:eu-repo/semantics/publishedVersion Zamora, Samuel (orcid)0000-0002-3917-4628 52, 1 (2024), 295-320 Annu. rev. earth planet. sci. ANNUAL REVIEW OF EARTH AND PLANETARY SCIENCES 0084-6597 10887471 http://zaguan.unizar.es/record/145576/files/texto_completo.pdf Versión publicada 1760056 http://zaguan.unizar.es/record/145576/files/texto_completo.jpg?subformat=icon icon Versión publicada oai:zaguan.unizar.es:145576 articulos driver 2026-02-17-20:46:03 ARTICLE