Acoel Flatworms: Earliest Extant Bilaterian Metazoans, Not Members of Platyhelminthes

1999/03/19 by Iñaki Ruiz‐Trillo, Marta Riutort, D. Timothy J. Littlewood +2 · 13 citations
Biochemistry, Genetics and Molecular Biology · #Planarian Biology and Electrostimulation #Genetics, Aging, and Longevity in Model Organisms #Protist diversity and phylogeny

paper · doi:10.1126/science.283.5409.1919

openalex publication_date 1999/03/19 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/23

Abstract

Because of their simple organization the Acoela have been considered to be either primitive bilaterians or descendants of coelomates through secondary loss of derived features. Sequence data of 18S ribosomal DNA genes from non-fast evolving species of acoels and other metazoans reveal that this group does not belong to the Platyhelminthes but represents the extant members of the earliest divergent Bilateria, an interpretation that is supported by recent studies on the embryonic cleavage pattern and nervous system of acoels. This study has implications for understanding the evolution of major body plans, and for perceptions of the Cambrian evolutionary explosion.

Citations

• Cases in which Parsimony or Compatibility Methods will be Positively Misleading
• Dating of the human-ape splitting by a molecular clock of mitochondrial DNA
• The genetic data environment an expandable GUI for multiple sequence analysis
• Table 1 in A new Gammarus species from Xinjiang Uygur Autonomous Region (China) with a key to Xinjiang freshwater gammarids (Crustacea, Amphipoda, Gammaridae)

Cited by

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• Deuterostome phylogeny reveals monophyletic chordates and the new phylum Xenoturbellida
• Constraining the Deep Origin of Parasitic Flatworms and Host-Interactions with Fossil Evidence
• Filling a gap in the phylogeny of flatworms: relationships within the Rhabdocoela (Platyhelminthes), inferred from 18S ribosomal DNA sequences
• Exceptionally preserved soft-bodied assemblage in Ordovician carbonates of Anticosti Island, eastern Canada
• Platyhelminthes ou apenas semelhantes a Platyhelminthes? Relações filogenéticas dos principais grupos de turbelários
• Dismissal of Acoelomorpha: Acoela and Nemertodermatida are separate early bilaterian clades
• Phylogeny of Catenulida and support for Platyhelminthes
• Platyhelminthes (Flatworms)
• Xenacoelomorpha is the sister group to Nephrozoa
• The Nemertodermatida are basal bilaterians and not members of the Platyhelminthes
• Genetic network of the eye in Platyhelminthes: expression and functional analysis of some players during planarian regeneration
• Invertebrate [wikipedia]