Clades for SIPUNCULA & MOLLUSCA
BILATERIAN ANIMALS (modified from WWW Tree of Life; traits & tree after Ruppert & Barnes 1994 p. 1052).
=========================== Platyhelminthes (flatworms, tapeworms, etc.) | | ====(branch uncertain)== pseudocoelomates (nematodes, rotifers, etc.) ====P=====| | | | | ================= Nemertea (ribbon worms) | | | | | ===| | ======== Sipuncula (peanut worms) | | | ==M==| | | | | ================================= TO MOLLUSCA ===> | ===C===| | <<=B=| | | ====== Echiura (proboscis worms) | | | | | B- BILATERIA =S?=| ===| === Pogonophora (beard worms, vent worms) | | | ===| | P- PROTOSTOMIA =S?=| === Annelida (segmented worms) | | | C- COELOMATE PROTOSTOME | ==== Onychophora (velvet worms) | =====| | S- SEGMENTATION ==== Arthropoda (insects, spiders, crabs, etc.) | ===================================== DEUTEROSTOMIA (echinoderms, chordates, etc.)
TRAITS SUPPORTING BRANCH
b) scraping buccal organ * c) muscular creeping foot * * traits b & c are only present in Sipuncula larvae |
======2================== Aplacophora (shell-less, worm-like molluscs) | <<=1===| ====4=============== Polyplacophora (chitons) | | ==3==| ====6=========== Monoplacophora (primitive limpet-like molluscs) | | =5==| ===9== Gastropoda (snails, slugs, etc.) | ==8==| | | ==10== Cephalopoda (nautiloids, cuttlefish, squids, octopus) ==7==| 5="CONCHIFERA" | ==12== Bivalvia (mussels, clams, scallops, etc.) ==11=| ==13== Scaphopoda (tusk shells)
(** plesiomorphic- a primitive state, not unique to clade): b) mantle with calcareous spicules produced by single cells, c) posterolateral mantle cavity with multiple bipectinate gills (ctenidia) d) radula e) larval/adult body with traces of eight segments f) trochophore larvae** g) coelom via schizocoely** h) 'open' circulatory system (hemocoel) with pumping heart i) circumpharyngeal nerve-ring (brain) with ladder-like ventrolateral nerves** b) reduction/loss of foot & head c) reduced # ctenidia (two or fewer) b) one or more dorsal, solid shell plates c) 8 pair pedal 'retractor' muscles d) mobile radular membrane & odontophore b) mantle girdle c) calcareous spicules from single cells** b) 3-layered shell (periostracum, prismatic & nacreous calcareous layers) c) crystalline style b) monopectinate ctenidia (5-6 pr.) |
b) 1 or 2 pr. ctenidia c) veliger larva (absent in Cephalopoda) b) dorsoventrally expanded body with large, dorsal viscera c) 1 pair pedal retractor muscles b) operculum attached to foot c) 1 pr. ctenidia** b) shell with gas-filled chambers & siphuncle c) ink gland d) beak-like jaws e) large, circumoral tentacles/arms f) 'closed' circulatory system (vessels lined by epithelium) g) image-forming eyes & large brain b) paired, lateral larval shell plates c) 1 pr. ctenidia** b) head lost c) enlarged mantle cavity & ctenidia d) mantle edge fused to shell e) byssal gland b) ctenidia lost c) captacula |
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Copyright © 2000 by A. Richard Palmer. All rights reserved.
(revised Jan. 18, 2000)