Chordata
From Microcosm Aquarium Explorer
[edit] The Chordates
Tunicates and True Vertebrates
Number of Living Species: 44,000.
Common Characteristics: members of the large Subphylum Vertebrata (true vertebrates), have a segmented backbone that protects a spinal cord; two small subphyla, including the tunicates or sea squirts, have a notochord (a hollow dorsal tube analogous to a true spinal cord) during part of their life cycle. These latter groups are generally lumped with the invertebrates.
Noteworthy Behaviors: true vertebrates have evolved some of the most complex anatomies, motor skills, intelligences, and behaviors in the Animal Kingdom.
They are Earth’s apex predators (although some biologists point out that the sheer mass and enormous molecular diversity of bacteria make them the dominant life forms on our planet).
Subphylum Urochordata (Tunicates): 1,600 species
Class Ascidiacea (Sea Squirts)
Class Thaliacea (Salps, Pyrosomes)
From: Reef Life by Denise Nielsen Tackett