Zoology 250 Phylogenetic Trees (2009)


(rotifer)

(nematode worm)
ASCHELMINTHES
(='pseudocoelomate' phyla)

(A grouping of convenience;
may not be monophyletic;
tree & most characters from
Nielson 1995
p. 62, 235, 262,
Brusca & Brusca 2003 p. 875,
Ruppert et al. 2004 p. 780, 804,
and Funch et al. 2005 Hydrobiologia 546:11-28).


(nematomorph worm)

(priapulid worm)


      = = = ==C== (branch uncertain) ==== Cycliophora ("small-wheel bearer"; newest phylum)

                      ===3=============== Rotifera (rotifers= "wheel bearers")
        |====2========|
        ?             ===4=============== Acanthocephala (spiny headed worms)
        |
<<==1===|   =============6=============== Gastrotricha (gastrotrichs, hairy-belly worms)
        |   |
        =5==|         ===9=============== Nematoda (round worms)
            |   ===8==|
            |   |     ==10=============== Nematomorpha (horsehair worms)
            |   |
            =7==|     ==12=============== Priapula (penis worms)ms)
                |     |
                ==11==|     ===14======== Kinorhyncha (spiny-snout propelled worms)
                      ==13==|
                            ===15======== Loricifera (corset-bearer worms)

Back to Zool 250 tree for animal phyla or Protostomia


TRAITS SUPPORTING EACH CLADE (** plesiomorphic- a primitive state, not unique to clade):
1:
a) triploblastic**
b) pseudocoelom
c) extracellular cuticle
d) bilaterally asymmetrical, determinate cleavage
e) mesoderm from blastopore rim
f) direct development
g) protonephridia**
C= CYCLIOPHORA (Symbion pandora):
a) acoelomate
b) sessile, filter-feeding rotifer-like adult
c) wheel-like ring of multiciliated cells surrounds the mouth
d) U-shaped gut
e) complex life cycle with sexual and asexual stages
f) unique Pandora larva
2:
a) trunk with intracellular skeletal lamina
        (extracellular cuticle absent)
b) sperm have anterior flagella!
c) syncytial epidermis
d) protonephridial terminal cell has multiple cilia
3= ROTIFERA:
a) head bears a ciliated corona
b) toes with adhesive glands
c) one ventral nerve cord
4= ACANTHOCEPHALA:
a) loss of gut due to parasitic lifestyle
b) apical proboscis with intracellular hooks
c) two lateral nerve cords
d) conspicuous introvert
5= CYCLONEURALIA
a) terminal mouth
b) radial pharynx
c) tripartite epipharyngeal brain
6= GASTROTRICHA:
a) myo-epithelial sucking pharynx
b) pseudocoelom lost
c) two lateral nerve cords
d) multilayered cuticle
7:
a) no locomotory cilia or ciliated epithelia
b) cuticle molted
c) introvert with cuticular spines, teeth or scalids
8:
a) collagenous cuticle
b) protonephridia lost
c) circular trunk muscles lost
d) non-ciliated sperm
9= NEMATODA:
a) 6+6+4 sensillae and amphids
b) four nerve cords (dorsal, ventral, 2 lateral)
10= NEMATOMORPHA:
a) gut rudimentary or absent in adults
b) no amphids
c) one ventral nerve cord
11:
a) conspicuous introvert
b) rings of scalids on introvert
c) chitinous cuticle
d) one ventral nerve cord
12= PRIAPULA:
a) large body cavity with amoebocytes and erythrocytes
b) unique caudal appendage
c) unique loricate larva
13:
a) mouth cone with cuticular ridges and spines
b) circular trunk muscles lost
14= KINORHYNCHA:
a) segmented body (13 segments)
15= LORICIFERA:
a) scalids with muscles
b) tri-radiate, myo-epithelial sucking pharynx


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

Copyright (c) 2009 by A. Richard Palmer. All rights reserved.
(revised Dec. 25, 2008)