Phylogeny of Chordata
1. Chordata: Bilateral symmetry, segmented body and muscles, well developed coelom and complete hemal system and digestive system. The main characteristic of chordates is the presence of a hollow nerve chord (notochord) at some point in their life cycle (e.g. in larval stage for A. glabra).
2. Metameria: Segmentation (metamerism).
3. Cephalochordata: Notochord extended into the anterior extremity of the body (rostrum).
4. Vertebrata: Multi-layered epithelia. Presence of kidneys.
5. Tunicata: Presence of a tunic, reversed heartbeat. Loss of the nephridia and the coelom. Mostly hermaphroditic, gonads in the gut loop, determinate development.
6. Longitudinal branchial blood vessels.
7. Stolodobranchia: Neural gland located dorsally to the cerebral ganglion. Single atrial developmental invagination.
8. Papillae and longitudinal branchial vessels associated.
9. Phlebobranchia: Unpaired gonads.
10. Thaliacea: Reduced larvae, budding arising from the epicardia sac.
11. Horizontal tail, early differentiation of the larvae into tadpole, larvae papillae aligned in the mid-sagittal axis.
12. Aplousobranchia: Zooid body plan segmented in two or three. Gonads located in the abdomen or post abdomen.
13. Appendicularia: Filter-feeding appendice made of mucus.
Based and adapted from Ruppert et al., 2004
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