Z250- 'Pseudocoelomates' Clade (2017)

Zoology 250 Phylogenetic Trees (2017)

(rotifer)

(nematode worm)

ASCHELMINTHES*
(='Pseudocoelomate' phyla)

(A grouping of convenience;
not a monophyletic group*;
tree and most traits modified from
Nielson 2012 p. 180, 272,
Brusca and 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)
        ?
        ?================5=============== Gastrotricha (gastrotrichs, hairy-belly worms)
        ?
<<==1===|             ===8=============== Nematoda (round worms)
        |       ===7==|
        |       |     ===9=============== Nematomorpha (horsehair worms)
        |       |
        =====6==|     ==11=============== Priapula (penis worms)ms)
                |     |
                ==10==|     ===13======== Kinorhyncha (spiny-snout propelled worms)
                      ==12==|
                            ===14======== 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) AND HIGHER TAXA:

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= GNATHIFERA 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= GASTROTRICHA: a) myo-epithelial sucking pharynx
b) pseudocoelom lost
c) two lateral nerve cords
d) multilayered cuticle

6= CYCLONEURALIA: a) terminal mouth
b) radial pharynx
c) collar-shaped brain
d) no locomotory cilia or ciliated epithelia
e) chitinous cuticle
f) cuticle molted
g) introvert with cuticular spines, teeth or scalids

7: a) collagenous cuticle
b) protonephridia lost
c) circular trunk muscles lost
d) non-ciliated sperm

8= NEMATODA: a) 6+6+4 sensillae and amphids
b) four nerve cords (dorsal, ventral, 2 lateral)
c) four moults (Nielsen 2012)

9= NEMATOMORPHA: a) gut rudimentary or absent in adults
b) no amphids
c) one ventral nerve cord
d) one moult (Nielsen 2012)

10: a) conspicuous introvert
b) rings of scalids on introvert
c) one ventral nerve cord
d) 2 rings of pharynx retractors penetrate brain

11= PRIAPULA: a) large body cavity with amoebocytes and erythrocytes
b) unique caudal appendage
c) unique loricate larva

12: a) mouth cone with cuticular ridges and spines
b) circular trunk muscles lost

13= KINORHYNCHA: a) segmented body (13 segments)

15= LORICIFERA: a) scalids with muscles
b) tri-radiate, myo-epithelial sucking pharynx

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