Section III: Beyond Segmentation
Segmental Traits in Non-Segmented Bilaterians
Bruno C. Vellutini
CONTENTS
- 9.1 Background...................................................................................................206
- 9.2 What Is Segmental?......................................................................................207
- 9.3 Xenacoelomorpha.........................................................................................208
- 9.4 Deuterostomia...............................................................................................209
- 9.4.1 Hemichordata (Acorn Worms)..........................................................209
- 9.4.2 Echinodermata (Sea Urchins, Sea Stars, and Others)......................212
- 9.4.3 Cephalochordata (Lancelets or Amphioxi)......................................213
- 9.4.4 Tunicata (Sea Squirts and Salps)......................................................213
- 9.5 Ecdysozoa.....................................................................................................214
- 9.5.1 Nematoda (Round Worms)...............................................................214
- 9.5.2 Nematomorpha (Horsehair Worms).................................................216
- 9.5.3 Priapulida (Penis Worms).................................................................216
- 9.5.4 Kinorhyncha (Mud Dragons)............................................................217
- 9.5.5 Loricifera (Girdle Wearers)..............................................................218
- 9.5.6 Tardigrada (Water Bears).................................................................218
- 9.5.7 Onychophora (Velvet Worms)...........................................................219
- 9.6 Spiralia..........................................................................................................221
- 9.6.1 Chaetognatha (Arrow Worms)..........................................................221
- 9.6.2 Rotifera (Wheel Worms)...................................................................221
- 9.6.3 Micrognathozoa (Jaw Animals)........................................................223
- 9.6.4 Gastrotricha (Hairybacks)................................................................224
- 9.6.5 Platyhelminthes (Flatworms)............................................................224
- 9.6.6 Nemertea (Ribbon Worms)...............................................................226
- 9.6.7 Mollusca (Snails and Squids)............................................................227
- 9.6.8 Brachiopoda (Lamp Shells)..............................................................231
- 9.6.9 Phoronida (Horseshoe Worms).........................................................232
- 9.6.10 Bryozoa (Moss Animals)..................................................................232
- 9.7 Discussion.....................................................................................................232
Acknowledgments..................................................................................................236
References..............................................................................................................236
