4 Phylogeny of Animals
123
Anthozoa
Scyphozoa
Hydrozoa
Porifera
Chaetognatha
Hemichordata
Echinodermata
Urochordata
Cephalochordata
Vertebrata
Brachiopoda
Entoprocta
Phoronida
Ectoprocta
Nemertea
Platyhelminthes
Mollusca
Arthropoda
Annelida
Tentaculata
Articulata
Ecdsysozoa
Lophotrochozoa
Deuterostomia
Chordata
Coelomopora
Ctenophora
Coelenterata
Coelomate
enterocoelous &
deuterostome
ancestor
Porifera
Hemichordata
Echinodermata
Urochordata
Cephalochordata
Vertebrata
Brachiopoda
Entoprocta
Phoronida
Ectoprocta
Mollusca
Arthropoda
Annelida
Acoel
flatworm-like
ancestor
Anthozoa
Scyphozoa
Hydrozoa
Ctenophora
Deuterostomes
(Enterocoely)
Nemertea
Platyhelminthes
Chaetognatha
?
Protostomes
(Schizocoely)
Priapulida
Gnathostomulida
Gastrotricha
Rotifera
Nematodes
Kinorhynches
Priapulida
Gnathostomulida
Gastrotricha
Rotifera
Nematodes
Kinorhynches
Aschelminthes
Aschelminthes
Loss of coelom
(complete or partial)
Segmentation
Segmentation
Anthozoa
Scyphozoa
Hydrozoa
Porifera
Chaetognatha
Hemichordata
Echinodermata
Urochordata
Cephalochordata
Vertebrata
Brachiopoda
Entoprocta
Phoronida
Ectoprocta
Nemertea
Platyhelminthes
Mollusca
Arthropoda
Annelida
Ctenophora
Priapulida
Gnathostomulida
Gastrotricha
Rotifera
Nematodes
Kinorhynches
A
B
C
Fig. 4.2
Some historical schemes of metazoan phylogeny. (a) An extreme representation of the “traditional” textbook phylogeny assuming the progressive
divergence of increasingly complex forms of bilaterian animals from a triploblastic acoelomate ancestor. The main character underlying this view is the
establishment of body cavities, from Barnes (1974). (b) An archaecoelomate scheme of metazoan phylogeny. This view postulates an early origin of the
coelom and enterocoely as the ancestral mode of coelom formation, which results in organisms with such developmental features being at the base of the
tree (Marcus 1958). (c) The “new view” of metazoan phylogeny that splits all bilaterians into three main clades on the base of evidence from SSU molecular
phylogeny and Hox genes, from Adoutte et al. (2000)
123
Anthozoa
Scyphozoa
Hydrozoa
Porifera
Chaetognatha
Hemichordata
Echinodermata
Urochordata
Cephalochordata
Vertebrata
Brachiopoda
Entoprocta
Phoronida
Ectoprocta
Nemertea
Platyhelminthes
Mollusca
Arthropoda
Annelida
Tentaculata
Articulata
Ecdsysozoa
Lophotrochozoa
Deuterostomia
Chordata
Coelomopora
Ctenophora
Coelenterata
Coelomate
enterocoelous &
deuterostome
ancestor
Porifera
Hemichordata
Echinodermata
Urochordata
Cephalochordata
Vertebrata
Brachiopoda
Entoprocta
Phoronida
Ectoprocta
Mollusca
Arthropoda
Annelida
Acoel
flatworm-like
ancestor
Anthozoa
Scyphozoa
Hydrozoa
Ctenophora
Deuterostomes
(Enterocoely)
Nemertea
Platyhelminthes
Chaetognatha
?
Protostomes
(Schizocoely)
Priapulida
Gnathostomulida
Gastrotricha
Rotifera
Nematodes
Kinorhynches
Priapulida
Gnathostomulida
Gastrotricha
Rotifera
Nematodes
Kinorhynches
Aschelminthes
Aschelminthes
Loss of coelom
(complete or partial)
Segmentation
Segmentation
Anthozoa
Scyphozoa
Hydrozoa
Porifera
Chaetognatha
Hemichordata
Echinodermata
Urochordata
Cephalochordata
Vertebrata
Brachiopoda
Entoprocta
Phoronida
Ectoprocta
Nemertea
Platyhelminthes
Mollusca
Arthropoda
Annelida
Ctenophora
Priapulida
Gnathostomulida
Gastrotricha
Rotifera
Nematodes
Kinorhynches
A
B
C
Fig. 4.2
Some historical schemes of metazoan phylogeny. (a) An extreme representation of the “traditional” textbook phylogeny assuming the progressive
divergence of increasingly complex forms of bilaterian animals from a triploblastic acoelomate ancestor. The main character underlying this view is the
establishment of body cavities, from Barnes (1974). (b) An archaecoelomate scheme of metazoan phylogeny. This view postulates an early origin of the
coelom and enterocoely as the ancestral mode of coelom formation, which results in organisms with such developmental features being at the base of the
tree (Marcus 1958). (c) The “new view” of metazoan phylogeny that splits all bilaterians into three main clades on the base of evidence from SSU molecular
phylogeny and Hox genes, from Adoutte et al. (2000)