(brachiopod) |
(bryozoan) |
DEUTEROSTOMIA
(modified from Tree of Life; traits & tree after Ruppert et al. 2004 p. 220, 868 and Brusca & Brusca 2003 p. 875) |
(asteroid echinoderm) |
(enteropneust hemichordate) |
============================ Protostomia | <<===| ====1================== Chaetognatha (arrow worms) | | | |===2================== lophophorates (Ph. BRYOZOA, BRACHIOPODA, etc.) ==D==| | =========== ECHINODERMATA (starfish, urchins, sea cucumbers,etc.) | ==4==| ===3===| ===5======= HEMICHORDATA (acorn worms, pterobranchs) | ================ CHORDATA
Back to Zool 250 tree for animal phyla.
TRAITS SUPPORTING EACH CLADE (** plesiomorphic- a primitive state, not unique to clade):
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 d) postanal testes b) mesosome secretes covering (tube, shell, cuticle) c) reduction in prosome d) U-shaped gut |
b) tri-coelomate organization of larval stage** c) ciliated pharyngeal pores/gill slits d) post-anal tail e) stiffened, notochord-like structure f) gonads with separate gonoducts b) larval similarities (echinoderm auricularia & bipinnaria resemble enteropneust tornaria larvae) b) muco-ciliary pre-oral locomotory organ c) paired valved collar ducts d) ventral post-anal tail e) dorsal and ventral longitudinal nerve cords f) multiciliated cells (Enteropneusta only) |
$ Increasing evidence - both molecular and morphological - suggests the Chaetognatha and the 'lophophorate' phyla belong within the Protostomia rather than the Deuterostomia. Their placement within the Protostomia, however, remains much debated. They are placed in the Deuterostomia here to reflect the traditional view that, although they possess traits of both protostomes and deuterostomes, the morphological and developmental traits shared with deuterostomes outnumber those shared with protostomes.