Zoology 250 Phylogenetic Trees (2004)


(rotifer)
(nematode worm)

ASCHELMINTHES
(=pseudocoelomates)


(A grouping of convenience;
probably not monophyletic;
tree & most characters from
Nielson 1995 p. 62, 235, 262
and Brusca & Brusca 2003 p. 875)
(nematomorph worm)
(priapulid worm) 

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

Back to Zool 250 version of tree for animal phyla or Protostomia.

TRAITS SUPPORTING EACH CLADE (** plesiomorphic- a primitive state, not unique to clade):
1:
a) triploblastic**
b) pseudocoelom
c) bilaterally asymmetrical, determinate cleavage
d) mesoderm from blastopore rim
e) direct development without ciliated primary larva
f) protonephridia**
2:
a) trunk with intracellular skeletal lamina (extracellular cuticle absent)
b) sperm structure with anterior flagella
3 (Rotifera):
a) toes with adhesive glands
b) one ventral nerve cord
4 (Acanthocephala):
a) loss of gut
b) apical proboscis with intracellular hooks
c) two lateral nerve cords
5:
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
7:
a) no locomotory cilia
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
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

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Copyright © 2004 by A. Richard Palmer. All rights reserved.
(revised Dec. 23, 2003)