This week we will discuss Subphylum Vertebrata. In this group,
the nerve cord enlarges anteriorly to form a brain and vertebrae surround
or replace the notocord. Take special note that the taxonomy of the vertebrates
has been revised from seven classes to twelve clades (groups) based on
phylogenetic systematics or cladistics. As you know from your work
this quarter, cladistics is an approach to classification that relfects
recent origin from a common ancestor. The grouops are defined and their
relatedness is determined by the number of shared derived characteristics.
Your textbook uses the traditional classical evolutionary taxonomy (seven
vertebrae classes), but the cladistic approach is widely accepted because
it is more rigorous and less arbitrary in defining group relationships.
In this course we have time for only a brief overview of vertebrate taxonomy.
In the Bios 303 course, Comparative Vertebrate Anatomy, you will have the
opportunity to further explore this topic.
KINGDOM ANIMALIA: Phylum Chordata
Subphylum Vertebrata Clades
Class Myxinoidea (hagfishes)
Class Petromyzontida (lamprey)
Class Chondrichthyes (sharks,
rays, skates, chimeras)
Class Actinopterygii (rayfinned fishes like perch, bass, seahorse)
Class Actinista (coelacanths)
Class Dipnoi (lungfishes)
Class Amphibia (frogs, toads,
salamanders)
Class Mammalia (mammals)
Class Testudines (turtles,
tortoises)
Class Lepidosauromorpha (snakes, lizards)
Class Crocodilia (alligators,
crocodiles)
Class Aves (birds)