(platyhelminth worm) |
(nemertean worm) |
BILATERIA
(= bilaterally symmetric animals) |
(annelid worm) |
(pogonophoran worm) |
(gastropod mollusc) |
(sipunculan worm) |
(modified from
Tree of Life; traits & tree after Ruppert et al. 2004 p. 220, 420 Eernisse et al. 1992, and Brusca and Brusca 2003 p. 875). |
(echiuran worm) |
(crustacean arthropod) |
========================== Platyhelminthes (flatworms, tapeworms,etc. | | ===(branch uncertain)== 'pseudoceolomates' (nematodes, rotifers,etc.) | | ===P===| | ================ Nemertea (ribbon worms) | | | | | =1=| | ======= Mollusca (snails, clams, squids, etc.) | | | ==3==| | ===C===| | ======= Sipuncula (peanut worms)$ | | | <<=B=| B- BILATERIA | | == Annelida (segmented worms) | | | =6=| | P- PROTOSTOMIA =2==| =5=| == Pogonophora (beard worms, vent worms)$$ | S? | | | | C- COELOMATE =4==| ===== Echiura (proboscis worms) | PROTOSTOMES S? | | ==7===== Panarthropoda (velvet worms, insects, spiders, crabs, etc.) | S? ORIGIN OF | SEGMENTATION? ================================= Deuterostomia (echinoderms, chordates, etc.)
$ Boore & Staton. 2002. Mol. Biol. Evol. 19:127-137 suggest mtDNA gene order of Sipuncula may be more similar to annelids than to molluscs.
$$ now considered to be an order of polychaete annelids (in the Canipalpata)!
Back to Zool 250 tree for animal phyla
b) mesoderm from single (mesentoblast) cell c) fate of first germ cell set at 5th cleavage d) mouth (and sometimes anus) from blastopore e) sheets of sub-epidermal muscles f) multiciliated cells b) circumpharyngeal ganglia c) paired gonoducts d) circular muscle layer lies outside longitudinal muscle layer b) trochophore-like larva with apical cilia c) larvae swim with compound cilia b) entomesoblast cell yields paired coeloms (mesoderm) c) paired ventral nerve bundles d) dorsal contractile vessel or heart e) gonads lie in coeloms f) heart lies in coelomic pericardium g) metanephridial funnel opens in coelomic sac h) dorsal heart pumps anteriorly |
b) scraping buccal organ * c) muscular creeping foot * * traits b and c occur only in Sipuncula larvae b) anus-bearing pygidium/telson c) paired: ventral nerve cords with segmental ganglia (only in late larva & postlarva of Echiura), coelomic cavities, metanephrida, & gonads d) engrailed expression at posterior segm. margins b) protrusible epidermal, chitinous setae in setal sacs (only in opisthoma of pogonophorans) b) ventro-lateral legs (lobopods) with hooked tips c) must molt to grow d) similar chemical makeup of cuticle e) ectodermal cilia lost f) extensive hemocoel ('open' circulatory system), coeloms reduced g) heart with openings to hemocoel (ostia) h) panarthropodan sensilla i) superficial cleavage, no trochophore-like larva |