Zoology 250 Phylogenetic Trees (2011)


(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
b) dorso-ventral body axis
c) 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 sister group to the Medusozoa (=Hydrozoa + Cubozoa + Scyphozoa, all of which have a unique, linear mtDNA molecule; Martindale et al. 2002 Molec Phylog Evol 24: 358) but some morphological data contradict this relationship (Collins et al. 2006 Sys Biol 55:97). Stay tuned!


Return to Zool 250 Home Page or try your skill at the Invertebrate Diversity Quiz.

Copyright (c) 2011 by A. Richard Palmer. All rights reserved.
(revised Dec. 30, 2010)