Phylum Chordata

Phylum Chordata

• Deuterostomes• The four traits ALWAYS

– Notochord– Pharyngeal slits/pouches– Hollow, dorsal nerve cord– Postanal tail

• Other traits– Endostyle or thyroid gland– Segmental musculature

It’s What All the Chordates are Wearing

It’s What All the Chordates are Wearing

Stages & Events of Chordate EmbryogenesisDevelopmental Process Embryonic Stage

Fetus

NeurulationNeurulation

Zygote

Morula

Blastula

Gastrula

Neurula

Pharyngula

Cleavage Generates a Blastula

Gastrulation & Neurulation

Fates of Embryonic Germ Layers

Gastrulation & Neurulation

Notochord

• Embryonic mesodermal structure

• Induces neural tube formation• Serves as a dorsal support

structure

Notochord & Formation of Neural Tube

N

N

NTNT

NTNT

Pharyngula Staged Vertebrate Embryos

Chordate Cladistics

Phylogenetic Relationship between Echinoderms, Hemichordates & Chordates

Chordate Phylogeny

Phylum Chordata, Subphylum Urochordata

• Protochordates– SP Urochordata

• Notochord only in tail• Tadpole-like larvae

– Class Ascidiacea– Class Thaliacea– Class Larvacea

Ascidian

Thaliacian

Larvacian

Urochordate Larvae

Ascidian Larvae & Metamorphosis

Ascidian Adult Anatomy

Solitary AscidiansClavelina puertosecensis

Compound Tunicate Colony

Class Thaliacea (Salps)

Class Larvacea

The Ancestral Chordate

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Phylum Chordata Subphylum Cephalochordata

• Maintain chordate structures throughout life

• Segmental myomeres very apparent

• Notochord extends entire length of body

Amphioxus Maintains All Chordate Characters• Notochord• Dorsal neural tube• Pharyngeal slits/pouches originate from neural crest

– Analogous to gill slits, inner ear & larynx• Postanal tail

– Extension of body muscle beyond anal opening

tail

Amphioxus

Pikaia• Earliest known fossil chordate• Burgess shale of BC• Obvious similarity to

cephalochordates