Ambulacraria
Ambulacraria
Clade of deuterostomes containing echinoderms and hemichordates
Ambulacraria /ˌæmbjuːləˈkrɛəriə/, or Coelomopora /siːləˈmɒpərə/, is a clade of invertebrate phyla that includes echinoderms and hemichordates;[1] a member of this group is called an ambulacrarian. Phylogenetic analysis suggests the echinoderms and hemichordates separated around 533 million years ago.[2] The Ambulacraria are part of the deuterostomes, a clade that also includes the many Chordata, and the few extinct species belonging to the Vetulicolia.
The two living clades with representative organisms are:
- Echinodermata (sea stars, sea urchins, brittle stars, sea cucumbers, feather stars, sea lilies, etc.)
- Hemichordata (acorn worms, Pterobranchia, and possibly graptolites)
(These together sometimes are called the lower deuterostomes.[3])
Whether the Xenacoelomorpha clade is the sister group to the Ambulacraria remains a contentious issue, with some authors arguing that the former should be placed more basally among metazoans,[4][5][6] and other authors asserting that the best choices of phylogenetic methods support the position of Xenacoelomorpha as the sister group to Ambulacraria.[7][8]
Fossil taxa that may lie on the stem lineage:
- Superphylum Ambulacraria
- † "Cambroernids" (informal unranked clade)[9]
- Herpetogaster
- Phlogites
- "Eldoniids" / "Eldonioids"
- † "Cambroernids" (informal unranked clade)[9]