Ambulacraria
| Ambulacrarians Temporal range: | |
|---|---|
| Various sea stars and sea urchins among mussel shells in the rocky intertidal zone of Kachemak Bay, southern Alaska, United States | |
| Scientific classification | |
| Domain: | Eukaryota |
| Kingdom: | Animalia |
| Subkingdom: | Eumetazoa |
| Clade: | ParaHoxozoa |
| Clade: | Bilateria |
| Clade: | Nephrozoa |
| Superphylum: | Deuterostomia |
| Clade: | Ambulacraria Metschnikoff, 1881 |
| Phyla | |
Ambulacraria /ˌæmbjuːləˈkrɛəriə/, or Coelomopora /siːləˈmɒpərə/, is a clade of invertebrate phyla that includes echinoderms and hemichordates; a member of this group is called an ambulacrarian. Phylogenetic analysis suggests the echinoderms and hemichordates separated around 533 million years ago. 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.)
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, and other authors asserting that the best choices of phylogenetic methods support the position of Xenacoelomorpha as the sister group to Ambulacraria.
Fossil taxa that may lie on the stem lineage:
- Superphylum Ambulacraria
- † "Cambroernids" (informal unranked clade)
- Herpetogaster
- Phlogites
- "Eldoniids" / "Eldonioids"
- † "Cambroernids" (informal unranked clade)