Prehistoric Models: Early Chordates
Chordata are animals that possess a notochord (a flexible rod formed of a material similar to cartilage), a dorsal nerve cord, pharyngeal slits, and a post-anal tail. For simplicity I have included the infraphylum Agnatha meaning “without jaws“. Agnatha are more commonly referred to as jawless fish in the phylum Chordata, subphylum vertebrata.
Kingdom: Animalia – Phylum: Chordata – Family: Pikaiidae – Genus: Pikaia
(extinct primitive chordata)
Cambrian Period
Genus and Species: Pikaia gracilens “Pika Peak”
Pronounced: Pik-ay-ah
Named by: Charles Walcott, 1911
Classification: Phylum: Chordata – Family: Pikaiidae
Time: Middle Cambrian Period
Locality: Canada, British Columbia – Burges Shale
Size: 38 millimeters or 1.5 inches
Diet: Unknown
Agnatha “jawless fish”
Domain: Eukaryota – Kingdom: Animalia – Phylum: Chordata – Infraphylum: Agnatha – Class: Pteraspidomorphi – Subclass: Heterostraci – Order: Pteraspiformes – Suborder: Pteraspidoidei – Family: Pteraspididae
(heterostracan vertebrates)
Devonian Period
Genus: Pteraspis ”Wing shield”
Pronounced: Teh-rass-pis
Species:P. crou chi, P. rostratus, P. stensioei
Named by: Agassiz – 1835
Classification: Phylum: Chordata – Infraphylum: Agnatha – Class: Pteraspidomorphi – Subclass: Heterostraci – Order: Pteraspidiformes – Family: Pteraspidae
Known locations: Europe, particularly Belgium and Britain
Time period: Early to Middle Devonian (Lochkovian to Emsian)
Size: 20 centimetres long
Diet: Carnivore
Domain: Eukaryota – Kingdom: Animalia – Phylum: Chordata – Infraphylum: Agnatha – Clade: Cephalaspidomorphi – Class: Osteostraci
(osteostraci meaning: “bony shells”)
Late Silurian to End Devonian
