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Phylum: Chordata (vertebrates and relatives, including fish, mammals, birds, reptiles and amphibians)

Life > Eukaryotes > Opisthokonta > Metazoa (animals) > Bilateria > Deuterostomia

Chordates are characterized by having a reinforced rod running down their back called a notocord. During embryonic development of vertebrates, which make up the vast majority of chordates, this notocord becomes incorporated into the vertebral column. The conventional classifications place the living vertebrates in five classes and for convenience I have followed this classification here: 

Classification

Chordata

 
 

Urochordata (tunicates)

 

 
 

Cephalochordata (lancelets, amphioxus)

 

 
 

Craniata (animals with skulls)

 

 
   

Hyperotreti (hagfishes)

 

 
   

Vertebrata (vertebrates)

 

 
     

Hyperoartia (lampreys)

Previously included in the "Agnatha" (jawless fish).

 
     

# Euconodonta (conodonts)

Previously included in the "Agnatha" (jawless fish). Conodont animals were eal-like primitive jawless vertebrates that lived 520 to 190 million years ago. For many years they were only known from fossilised tooth-like structures (termed conodonts) and their true identity was only revealed once fossilised soft body parts were discovered in association with the conodonts. Conodont fossils are found worldwide and in southern Africa are know from the Soom Shale in the Cedarberg.

 
     

# Pteraspidomorphi

Previously included in the "ostracoderms" ("shell-skinned") within the "Agnatha" ("jawless" fish), both groups of which are now considered paraphyletic. Includes the Arandaspida, Astraspida, Eriptychiida, and Heterostraci.

 
     

# Thelodonti

Previously included in the "ostracoderms" within the "Agnatha" (jawless fish).

 
     

# Anaspida

Previously included in the "ostracoderms" within the "Agnatha" (jawless fish).

 
     

# Galeaspida

Previously included in the "ostracoderms" within "Agnatha" (jawless fish).

 
     

# Pituriaspida

Previously included in the "ostracoderms" within "Agnatha" (jawless fish).

 
     

# Osteostraci

Previously included in the "ostracoderms" within "Agnatha" (jawless fish).

 
     

Gnathostomata (jawed vertebrates)

Evolved from a jawless fish-like ancestor through the incorporation of the first gill arch into the margin of the mouth, thus enabling the fish to bite.

 
       

# Placodermi (armored jawed vertebrates)

In southern Africa, placoderms have been recorded from Early Devonian (in the Lower Bokkeveld shales) and from Late Devonian strata.

 
       

Chondrichthyes (sharks, rays, chimaeras)

 

       

Teleostomi (teleost fish)

 

 
         

# Acanthodii

Originated in the Silurian and went extinct in the Permian. Fossil remains of acanthodians (spines, scale impressions, skull remnants, rarely articulated skeletons) have been recorded from Devonian and Carboniferous shallow marine, estuarine and lake deposits in South Africa.

 
         

Osteichthyes (bony fish)

 

 
           

Actinopterygii (ray-finned fish)

 

 
           

Sarcopterygii (lobe-finned fishes and four-legged vertebrates)

 

Publications

  • Durand, J.F. 2005. Major African contributions to Palaeozoic and Mesozoic vertebrate palaeontology. Journal of African Earth Sciences  43: 53-82.

Text by Hamish Robertson


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