Clades for DEUTEROSTOMIA & CHORDATA
BILATERIAN ANIMALS (modified from WWW Tree of Life; traits & tree after Ruppert & Barnes 1994 p. 1052 and Brusca & Brusca 1990 p.873).
==C============== coelomate protostomes (arthropods, annelids, molluscs, etc.) ======| ==P==| ================= Platyhelminthes (flatworms, tapeworms, etc.) | | | =(placement uncertain)= pseudocoelomates (nematodes, rotifers, etc.) <<===| | =1===================== Chaetognatha (arrow worms) | | ==D==| =3================= Lophophorates (Ph. Bryozoa, Brachiopoda, etc.) | | =2==| =========== Echinodermata (starfish, urchins, sea cucumbers,etc.) | =5==| =4==| ===6======= Hemichordata (acorn worms, pterobranchs)) | ============================================== TO CHORDATA ===>
(** plesiomorphic- a primitive state, not unique to clade): b) mesoderm from mesenchyme cells c) mouth (and sometimes anus) from blastopore d) multiciliated cells e) trochophore-like larva b) coelom via enterocoely c) blastopore yields anus d) tripartite coelom ----> tripartite body plan protocoel=axocoel ----> protosome mesocoel=hydrocoel ----> mesosome metacoel=somatocoel ----> metasome e) monociliated cells** b) grasping spines around mouth c) ventral ganglion b) reduction in prosome c) U-shaped gut |
b) protocoel has external coelomopore c) tri-coelomate organization of larval stage** d) ciliated pharyngeal pores/gill slits e) post-anal tail f) stiffened, notochord-like structure g) gonads with separate gonoducts b) protocoel has external coelomopore c) arval similarities (echinoderm auricularia & bipinnaria resemble enteropneust tornaria larvae) b) mucocciliary pre-oral locomotory organ c) paired valved collar ducts d) ventral post-anal tail |
Phylum CHORDATA (tree from WWW Tree of Life; traits from Brusca & Brusca 1990 p.873).
======= Cl. Larvacea (the appendicularians) ==1== UROCHORDATA =====| | | === Cl. Thaliacea (salps, doliolids, pyrosomes) | ==2=| | === Cl. Ascidiacea (sea squirts) <<=C==| | ==4======================= CEPHALOCHORDATA (lancelets) =3==| | ====== Myxini (hagfish) ==5== VERTEBRATA ===| ====== other vertebrates (fish, amphibians, reptiles, birds, mammals)
(** plesiomorphic- a primitive state, not unique to clade): b) cephalization c) notochord d) dorsal, somatic post-anal tail** e) dorsal hollow nerve cord f) pharynx with ciliated U-shaped gill slits** g) endostyle (thyroid gland in vertebrates) h) protocoelic nephridium (=axial complex) lost i) metacoel lost (i.e., coelom not tripartite) b) outer acellular tunic or temporary house c) 2 (Larvacea) or 1 (Ascidiacea) exhalent siphons or spiracles from pharynx d) U-shaped gut e) gill-slits no longer U-shaped f) primitive sperm morphology g) dstrict cell fate determination |
b) differentiation of neural tube c) ciliated, U-shaped gill slits** b) unusual protonephridia-like nephridia b) full endoskeleton with cranium c) anterior end of neural tube enlarged as brain d) polar bodies from oral pole |
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Copyright © 2002 by A. Richard Palmer. All rights reserved.
(revised April 3, 2002)