(sea gooseberry ctenophore)

BASAL METAZOA modified from Tree of Life; traits & tree after Ruppert & Barnes 1994 p. 1052)

(sea butterfly ctenophore)

         ======================================== Porifera (sponges)
         |
<<=M=====|    ====P============================== Placozoa (placozoans, Trichoplax)
         |    |
         ==1==|    =============================================== TO CNIDARIA ===>
              ==E==|
                   |     =====C================== Ctenophora (comb-jellies)
 M= METAZOA        ==2===|
 E= EUMETAZOA            ======================== Bilateria (all higher animals)

Back to Zool 250 tree for animal phyla

TRAITS SUPPORTING EACH CLADE
(** plesiomorphic- a primitive state, not unique to clade):

1: a) motile adults; dorso-ventral body axis, true radial symmetry P= PLACOZOA: a) flattened, discoidal body b) diploblastic** c) outer surfaces not true epithelia (no basal lamina) 2: a) acetylcholine / acetylcholinesterase system C= CTENOPHORA: a) diploblastic** b) blind gut** c) giant compound cilia form comb rows d) colloblast cells e) pair of elongate tentacles in tentacle sheaths f) biradial symmetry g) multiciliated cells*

(Obelia polyps + medusa)

(hydrozoan medusa)

PHYLUM CNIDARIA (= anemones, jellyfish, etc) (tree and traits from Ruppert et al. 2004)

(anthozoan polyp)

(scyphozoan medusa)

---

        ==2============== Hydrozoa (hydroids, siphonophores, hydrocorals, etc.)
        |
<<==1===|    ==4========= Anthozoa$ (anemones, corals, gorgonians, etc.)
        ==3==|
             |    ===6=== Cubozoa (sea wasps)
             ==5==|
                  ===7=== Scyphozoa (jellyfish)

Back to Zool 250 tree for animal phyla

TRAITS SUPPORTING EACH CLADE (** plesiomorphic- a primitive state, not unique to clade):

1= CNIDARIA: a) epidermal cnidocytes with nematocysts b) nematocyst with operculum c) diploblastic** and radial symmetry** 2= HYDROZOA: a) velum in medusa b) stenotele nematocyst c) simple bell margin in medusa, no rhopalia** d) simple gastrovascular cavity in polyp** e) medusa by simple budding f) medusa has simple manubrium g) cnidocytes strictly epidermal (gastrodermis lacks cnidocytes)** h) mesoglea lacks cells i) gonads epidermal 3: a) mesoglea contains cells b) gastrodermal cnidocytes in both polyp & medusa stage c) gastric filaments with cnidocytes d) gastrodermal gonads e) septate gastrovascular cavity in polyp f) true myocytes migrate to mesoglea

4= ANTHOZOA: $ a) medusa stage absent b) nematocysts lack operculum c) tubular pharynx with siphonoglyph in polyp 5= MEDUSOZOA: a) medusa stage dominant b) funnel-shaped polyp c) medusae produced by strobilation d) medusa with 4 septa and septal funnels e) 8 gonadal bands on septae f) rhopalia 6= CUBOZOA: a) cubic-shaped medusae b) small polyps lack septae c) tentacles on pedalia at corners of bell d) 4 rhopalia with complex ocelli e) velarium (velum-like structure in medusae) f) highly venomous nematocysts 7= SCYPHOZOA: a) polyps possess 4 septae b) large manubrium on medusae c) 8-fold notched bell margin with rhopalia

$Molecular data suggest Anthozoa are the sister group to the Medusozoa (=Hydrozoa + Cubozoa + Scyphozoa) and some morphological data support this relationship (Martindale et al. 2002. Molec Phylog. Evol. 24: 358).