User:R. S. Shaw/sandbox2

A modern consensus phylogenetic tree for Bilateria is shown below, although the positions of certain clades are still controversial (dashed lines) and the tree has changed considerably since 2000.

Planulozoa

Cnidaria  Bilateria  †Proarticulata  Xenacoelomorpha  Xenoturbellida  Acoelomorpha    Nemertodermatida Acoela  Nephrozoa   Deuterostomia   Chordata  Cephalochordata  Olfactores    Urochordata Craniata / Vertebrata  Ambulacraria    Echinodermata Hemichordata †Cambroernida   †Saccorhytus coronarius   †Vetulocystids †Vetulicolians  Protostomia   Ecdysozoa     Nematoida    Nematoda Nematomorpha Loricifera  Panarthropoda  Onychophora  Tactopoda    Tardigrada Arthropoda  Scalidophora    Priapulida Kinorhyncha > 539 Mya  Spiralia   Gnathifera    Rotifera and allies Chaetognatha  Platytrochozoa  Platyhelminthes and allies  Lophotrochozoa    Mollusca Annelida and allies ¿†Kimberella? 550 mya 580 Mya ¿†Kimberella? 610 mya 650 Mya

680 Mya

A different hypothesis is that the Ambulacraria are sister to Xenacoelomorpha together forming the Xenambulacraria. The Xenambulacraria may be sister to the Chordata or to the Centroneuralia (corresponding to Nephrozoa without Ambulacraria, or to Chordata + Protostomia). The phylogenetic tree shown below depicts the latter proposal. Also, the validity of Deuterostomia (without Protostomia emerging from it) is under discussion. The cladogram indicates approximately when some clades radiated into newer clades, in millions of years ago (Mya). While the below tree depicts Chordata as a sister group to Protostomia according to analyses by Philippe et al., the authors nonetheless caution that "the support values are very low, meaning there is no solid evidence to refute the traditional protostome and deuterostome dichotomy".

ParaHoxozoa

Placozoa Cnidaria  Bilateria  †Proarticulata  Xenambulacraria   Xenacoelomorpha  Xenoturbellida  Acoelomorpha    Nemertodermatida Acoela  Ambulacraria    Echinodermata Hemichordata †Cambroernida  Centroneuralia   Chordata  Cephalochordata  Olfactores    Urochordata Craniata / Vertebrata  Protostomia   Ecdysozoa     Nematoida    Nematoda Nematomorpha Loricifera  Panarthropoda  Onychophora  Tactopoda    Tardigrada Arthropoda  Scalidophora    Priapulida Kinorhyncha > 539 Mya Spiralia  Gnathifera    Rotifera and allies Chaetognatha  Platytrochozoa  Platyhelminthes and allies  Lophotrochozoa    Mollusca Annelida and allies ¿†Kimberella? 550 Mya 580 Mya ¿†Kimberella? 610 Mya   †Saccorhytus coronarius   †Vetulocystids †Vetulicolians 650 Mya

680 Mya