The Radiata and the evolutionary origins of the bilaterian body plan.

  title={The Radiata and the evolutionary origins of the bilaterian body plan.},
  author={Mark Q. Martindale and John R. Finnerty and Jonathan Q. Henry},
  journal={Molecular phylogenetics and evolution},
  volume={24 3},
A simple plan — cnidarians and the origins of developmental mechanisms
Cnidarian sequencing projects are showing that the common metazoan ancestor was more genetically complex than was previously assumed, and molecular genetic approaches are blurring the developmental divide between cnidarians and bilateral animals.
The dawn of bilaterian animals: the case of acoelomorph flatworms
  • J. Baguñá, M. Riutort
  • Biology
    BioEssays : news and reviews in molecular, cellular and developmental biology
  • 2004
An alternative view is discussed, in which acoelomorph flatworms, which do not belong to the Platyhelminthes, represent the earliest extant bilaterian clade, and this reconstruction backs the old planuloid–acoeloid hypothesis and may help the understanding of the evolution of body axes, Hox genes and the Cambrian explosion.
The evolution of multicellularity and early animal genomes.
The Cambrian "explosion" of metazoans and molecular biology: would Darwin be satisfied?
The origins of metazoan bodyplans and the extent to which they are coincident with the Cambrian "explosion" are both areas of continuing debate and molecular and developmental biology offer other unique insights, but may be problematic in terms of conflicting phylogenetic signals and questions.
Characterization of the Hox patterning genes in acoel flatworms
The posterior Hox genes were used to specify and maintain defined anatomical regions within the AP axis of animals since the beginning of bilaterian evolution, and how the morphological transition from radial to bilateral animals took place is concluded.
An integrated view of precambrian eumetazoan evolution.
A strong conclusion is that the evolutionary process generating the genomic programs responsible for developmental formulation of basic eumetazoan body plans was in many ways very different from the evolutionary changes that can be observed at the species level in modern animals.
Ancestral state reconstruction of ontogeny supports a bilaterian affinity for Dickinsonia
This study formalizes the connection between ontogeny in Dickinsonia—which grows by the addition of metameric units onto one end of its primary axis—with terminal addition, defined as growth and patterning from a posterior, subtermial growth zone, and concludes that terminal addition is a synapomorphy of bilaterian animals.
Hox, Wnt, and the evolution of the primary body axis: insights from the early-divergent phyla
The hypothesis that Wnt genes may be the earliest primary body axis patterning mechanism by suggesting that Hox genes were co-opted into this patterning network prior to the last common ancestor of cnidarians and bilaterians is extended.
Tempo and mode of early animal evolution: inferences from rocks, Hox, and molecular clocks
Abstract One of the enduring puzzles to Stephen Jay Gould about life on Earth was the cause or causes of the fantastic diversity of animals that exploded in the fossil record starting around 530


Acoel flatworms: earliest extant bilaterian Metazoans, not members of Platyhelminthes.
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.
Monophyletic origins of the metazoa: an evolutionary link with fungi
A phylogenetic framework inferred from comparisons of small subunit ribosomal RNA sequences describes the evolutionary origin and early branching patterns of the kingdom Animalia and shows the animal lineage is monophyletic and includes choanoflagellates.
The early emergence of platyhelminths is contradicted by the agreement between 18S rRNA and Hox genes data.
  • G. Balavoine
  • Biology
    Comptes rendus de l'Academie des sciences. Serie III, Sciences de la vie
  • 1997
Class-level relationships in the phylum Cnidaria: evidence from mitochondrial genome structure.
The structure of the mitochondrial genome in representatives of the four extant cnidarian classes and in the phylum Ctenophora is surveyed, finding that all anthozoan species tested possess mtDNA in the form of circular molecules, whereas all scyphozoan, cubozoa, and hydrozoan species tested display mt DNA in the forms of linear molecules.
Cnidarian homeoboxes and the zootype
A series of phylogenetic analyses indicate that Cnidaria, thought to be the earliest-evolving animal phylum with the exception of the sponges, lack several HOX genes that are present in Drosophila and vertebrates.
Ancient origins of axial patterning genes: Hox genes and ParaHox genes in the Cnidaria
Among the bilaterally symmetrical, triploblastic animals (the Bilateria), a conserved set of developmental regulatory genes are known to function in patterning the anterior–posterior (AP) axis. This
Cnidarians Reveal Intermediate Stages in the Evolution of Hox Clusters and Axial Complexity1
The linkage of eve to a Hox gene, a condition previously described in a coral, is found in vertebrates but apparently absent in insects.
Class-level relationships in the phylum Cnidaria: molecular and morphological evidence.
Analysis of class-level relationships based on 18S ribosomal DNA sequences, mitochondrial 16S rDNA sequence, mitochondrial genome structure, and morphological characters unifies the classes possessing a medusa stage, leaving the holobenthic Anthozoa basal within the phylum.
Evaluating multiple alternative hypotheses for the origin of Bilateria: an analysis of 18S rRNA molecular evidence.
  • A. Collins
  • Biology
    Proceedings of the National Academy of Sciences of the United States of America
  • 1998
Six alternative hypotheses for the phylogenetic origin of Bilateria are evaluated by using complete 18S rRNA gene sequences for 52 taxa to suggest that there is little support for three of these hypotheses, but one is most strongly supported.
The unique developmental program of the acoel flatworm, Neochildia fusca.
An understanding of the cell-lineage fate map allows the results of earlier cell deletion studies examining the specification of cell fates within these embryos to be interpreted and reveals the existence of cell-cell inductive interactions in these embryos.