Biology and Evolution of the Mollusca, Volume 2

This volume provides individual treatments of the major molluscan taxa. Each chapter provides an overview of the evolution, phylogeny and classification of a group of molluscs, as well as more specific and detailed coverage of their biology (reproduction, feeding and digestion, excretion, respiration etc.), their long fossil record and aspects of their natural history. The book is illustrated with hundreds of colour figures. In both volumes, concepts are summarised in colour-coded illustrations.

Key selling features:

• Comprehensively reviews molluscan biology and evolutionary history



• Includes a description the anatomy and physiology of anatomical systems



• Up to date treatment with a comprehensive bibliography



• Reviews the phylogenetic history of the major molluscan lineages

Contents

About the Authors......................................................................................................................................................................xvii

Introduction to Volume Two.......................................................................................................................................................xix

Chapter 12 Molluscan Relationships.......................................................................................................................................... 1

12.1 The Hypothetical Ancestral Mollusc............................................................................................................. 1

12.2 Hypotheses of Phylogenetic Relationships of the Major Molluscan Groups................................................ 1

12.2.1 Aculifera – Conchifera, Testaria, and Serialia Hypotheses............................................................. 4

12.2.2 The Search for the Molluscan Sister Group..................................................................................... 6

12.3 Repetition of Organs..................................................................................................................................... 8

12.4 Ano-Pedal Flexure and a Change in Body Orientation................................................................................. 9

12.5 Reduction and Paedomorphosis.................................................................................................................... 9

Chapter 13 Early History and Extinct Groups.......................................................................................................................... 11

13.1 Introduction................................................................................................................................................. 11

13.1.1 The First Molluscs?........................................................................................................................ 12

13.1.2 Shell Morphology........................................................................................................................... 13

13.1.2.1 Beyond Shell Morphology............................................................................................ 14

13.1.2.2 Muscle Scars................................................................................................................. 16

13.1.3 Phylogenetics and Fossils............................................................................................................... 18

13.2 Originations, Extinctions, and Recoveries.................................................................................................. 18

13.3 The Molluscan Fossil Record...................................................................................................................... 20

13.3.1 Ediacaran........................................................................................................................................ 20

13.3.2 Cambrian........................................................................................................................................ 22

13.3.2.1 Biomineralisation.......................................................................................................... 24

13.3.2.2 Taxa............................................................................................................................... 25

13.3.3 Ordovician...................................................................................................................................... 51

13.3.3.1 Taxa............................................................................................................................... 52

13.3.4 Silurian........................................................................................................................................... 55

13.3.4.1 Taxa............................................................................................................................... 55

13.3.5 Devonian........................................................................................................................................ 59

13.3.5.1 Taxa............................................................................................................................... 59

13.3.6 Carboniferous................................................................................................................................. 61

13.3.6.1 Taxa............................................................................................................................... 62

13.3.7 Permian.......................................................................................................................................... 64

13.3.7.1 Extinction...................................................................................................................... 64

13.3.7.2 Taxa............................................................................................................................... 65

Chapter 14 Polyplacophora, Monoplacophora, and Aplacophorans......................................................................................... 67

14.1 Introduction................................................................................................................................................. 67

14.2 Polyplacophora (Chitons, Placophora, Loricata, Amphineura in Part)....................................................... 67

14.2.1 Introduction.................................................................................................................................... 67

14.2.2 Phylogeny and Classification.......................................................................................................... 67

14.2.2.1 Sister Group Relationships............................................................................................ 69

14.2.3 Morphology.................................................................................................................................... 69

14.2.3.1 Shell and Girdle............................................................................................................. 70

14.2.3.2 Head-Foot, Muscles, and Mantle.................................................................................. 70

14.2.3.3 Mantle Groove (Mantle Cavity).................................................................................... 72

14.2.3.4 Digestive System........................................................................................................... 72

14.2.3.5 Renopericardial System................................................................................................. 75

14.2.3.6 Reproductive System..................................................................................................... 76

14.2.3.7 Nervous System and Sense Organs............................................................................... 78

14.2.3.8 Chromosomes................................................................................................................ 82

14.2.4 Biology, Ecology, and Behaviour................................................................................................... 82

14.2.4.1 Habits and Habitats....................................................................................................... 82

14.2.4.2 Locomotion................................................................................................................... 82

14.2.4.3 Feeding and Diet........................................................................................................... 82

14.2.4.4 Reproduction, Development, and Growth..................................................................... 83

14.2.4.5 Associations................................................................................................................... 84

14.2.4.6 Predators, Defence, and Behaviour............................................................................... 84

14.2.5 Diversity and Fossil History........................................................................................................... 84

14.3 The Monoplacophora (= Tryblidia, Neopilinida, Tergomya in part)........................................................... 84

14.3.1 Introduction.................................................................................................................................... 84

14.3.2 Phylogeny and Classification.......................................................................................................... 84

14.3.2.1 Sister Group Relationships............................................................................................ 85

14.3.3 Morphology.................................................................................................................................... 86

14.3.3.1 Shell and Protoconch..................................................................................................... 86

14.3.3.2 Head-Foot and Mantle................................................................................................... 87

14.3.3.3 Mantle Groove (Mantle Cavity).................................................................................... 88

14.3.3.4 Digestive System........................................................................................................... 89

14.3.3.5 Renopericardial and Reproductive Systems.................................................................. 90

14.3.3.6 Nervous System and Sense Organs............................................................................... 90

14.3.4 Biology, Ecology, and Behaviour................................................................................................... 91

14.3.4.1 Habits and Habitats....................................................................................................... 91

14.3.4.2 Feeding and Diet........................................................................................................... 92

14.3.4.3 Reproduction, Development, and Growth..................................................................... 92

14.3.4.4 Associations................................................................................................................... 92

14.3.4.5 Predation, Defence, and Other Behavioural Attributes................................................. 93

14.3.5 Diversity and Fossil History........................................................................................................... 93

14.4 Caudofoveata and Solenogastres: The Aplacophoran Groups.................................................................... 93

14.4.1 Introduction.................................................................................................................................... 93

14.4.2 Phylogeny and Classification.......................................................................................................... 94

14.4.3 Morphology.................................................................................................................................... 96

14.4.3.1 Head-Foot and Mantle................................................................................................... 96

14.4.3.2 Digestive System........................................................................................................... 97

14.4.3.3 Renopericardial and Reproductive Systems.................................................................. 97

14.4.3.4 Nervous System............................................................................................................. 97

14.4.3.5 Development.................................................................................................................. 98

14.4.3.6 Habits and Habitats....................................................................................................... 98

14.5 Caudofoveata (or Chaetodermomorpha, Scutopoda).................................................................................. 99

14.5.1 Introduction.................................................................................................................................... 99

14.5.2 Phylogeny and Classification.......................................................................................................... 99

14.5.2.1 Sister Group Relationships............................................................................................ 99

14.5.3 Morphology.................................................................................................................................... 99

14.5.3.1 Spicules......................................................................................................................... 99

14.5.3.2 Head-Foot and Mantle................................................................................................... 99

14.5.3.3 Mantle Cavity................................................................................................................ 99

14.5.3.4 Digestive System......................................................................................................... 100

14.5.3.5 Renopericardial and Reproductive Systems.................................................................101

14.5.3.6 Nervous System and Sense Organs..............................................................................101

14.5.4 Biology, Ecology, and Behaviour..................................................................................................101

14.5.4.1 Habits and Habitats......................................................................................................101

14.5.4.2 Feeding and Diet..........................................................................................................101

14.5.4.3 Reproduction, Development, and Growth................................................................... 102

14.5.4.4 Associations................................................................................................................. 102

14.5.5 Diversity and Fossil History......................................................................................................... 102

14.6 Solenogastres (or Neomeniomorpha)........................................................................................................ 102

14.6.1 Introduction.................................................................................................................................. 102

14.6.2 Phylogeny and Classification........................................................................................................ 102

14.6.2.1 Sister Group Relationships.......................................................................................... 102

14.6.3 Morphology.................................................................................................................................. 102

14.6.3.1 Spicules....................................................................................................................... 102

14.6.3.2 Body............................................................................................................................ 102

14.6.3.3 Mantle Cavity.............................................................................................................. 103

14.6.3.4 Digestive System......................................................................................................... 103

14.6.3.5 Renopericardial and Reproductive Systems................................................................ 104

14.6.3.6 Nervous System and Sense Organs............................................................................. 105

14.6.4 Biology and Ecology.................................................................................................................... 105

14.6.4.1 Habits and Habitats..................................................................................................... 105

14.6.4.2 Feeding and Diet......................................................................................................... 105

14.6.4.3 Reproduction, Development, and Growth................................................................... 105

14.6.4.4 Associations................................................................................................................. 107

14.6.5 Diversity and Fossil History......................................................................................................... 107

Chapter 15 The Bivalvia......................................................................................................................................................... 109

15.1 Introduction............................................................................................................................................... 109

15.2 Classification............................................................................................................................................. 109

15.3 Morphology................................................................................................................................................112

15.3.1 The Shell.......................................................................................................................................113

15.3.1.1 Orientation....................................................................................................................113

15.3.1.2 Sculpture.......................................................................................................................113

15.3.1.3 Shell Structure..............................................................................................................113

15.3.1.4 Periostracum.................................................................................................................115

15.3.1.5 Ligament.......................................................................................................................117

15.3.1.6 Hinge............................................................................................................................119

15.3.1.7 Pallial Line and Sinus.................................................................................................. 120

15.3.1.8 Shell Reduction, Accessory Shell Plates, and Secondary Shells................................. 120

15.3.2 Muscles and Their Scars.............................................................................................................. 124

15.3.3 The Foot....................................................................................................................................... 124

15.3.4 The Byssus – Structure and Function.......................................................................................... 125

15.3.5 Mantle and Siphons...................................................................................................................... 127

15.3.6 Mantle Cavity............................................................................................................................... 132

15.3.6.1 The Ctenidia – Their Structure and Ciliation.............................................................. 132

15.3.6.2 The Labial Palps.......................................................................................................... 139

15.3.6.3 Other Features of the Mantle Cavity............................................................................141

15.3.7 Digestive System...........................................................................................................................141

15.3.8 Renopericardial System................................................................................................................143

15.3.9 Reproductive System.....................................................................................................................143

15.3.10 Nervous System and Sense Organs.............................................................................................. 145

15.4 Biology and Ecology................................................................................................................................. 145

15.4.1 Habits and Habitats...................................................................................................................... 145

15.4.1.1 Locomotion................................................................................................................. 145

15.4.1.2 Attachment.................................................................................................................. 146

15.4.1.3 Secondary Soft-Bottom Dwellers.................................................................................147

15.4.1.4 Burrowers and Borers.................................................................................................. 149

15.4.2 Feeding......................................................................................................................................... 151

15.4.3 Life History and Growth.............................................................................................................. 152

15.4.4 Associations................................................................................................................................. 156

15.4.4.1 Bacterial and Algal Symbionts.................................................................................... 156

15.4.5 Relationships with Other Animals............................................................................................... 158

15.4.5.1 Predators of Bivalves................................................................................................... 159

15.5 Economic Values....................................................................................................................................... 159

15.6 Diversity and Fossil History...................................................................................................................... 159

15.6.1 The First Bivalves......................................................................................................................... 159

15.6.2 The Evolutionary Radiation of Bivalves...................................................................................... 159

15.6.2.1 Freshwater Bivalves.....................................................................................................161

15.6.3 Patterns of Bivalve Diversity.........................................................................................................161

15.7 The Protobranch Bivalves......................................................................................................................... 162

15.7.1 Phylogeny and Classification........................................................................................................ 162

15.7.2 Biology and Ecology.................................................................................................................... 163

15.7.3 Diversity and Fossil History......................................................................................................... 164

15.8 The Autobranch Bivalves.......................................................................................................................... 164

15.8.1 Pteriomorphia............................................................................................................................... 164

15.8.1.1 Phylogeny and Classification...................................................................................... 164

15.8.1.2 Biology and Ecology................................................................................................... 165

15.8.1.3 Diversity and Fossil History........................................................................................ 167

15.8.2 Heteroconchia............................................................................................................................... 167

15.8.3 Palaeoheterodonta........................................................................................................................ 168

15.8.3.1 Trigoniida.................................................................................................................... 168

15.8.3.2 Unionida...................................................................................................................... 168

15.8.4 Heterodonta...................................................................................................................................170

15.8.4.1 Archiheterodonta......................................................................................................... 172

15.8.5 Euheterodonta.............................................................................................................................. 172

15.8.5.1 Phylogeny and Classification.......................................................................................173

15.8.5.2 Biology and Ecology....................................................................................................174

15.8.5.3 Diversity and Fossil History.........................................................................................175

15.8.5.4 The Rudists...................................................................................................................175

15.8.6 Anomalodesmata (= Poromyata)...................................................................................................178

Chapter 16 The Scaphopoda................................................................................................................................................... 183

16.1 Introduction............................................................................................................................................... 183

16.2 Phylogeny and Classification.................................................................................................................... 183

16.2.1 Sister Group Relationships.......................................................................................................... 183

16.3 Morphology............................................................................................................................................... 184

16.3.1 Shell............................................................................................................................................. 184

16.3.2 Head-Foot, Captacula, and Mantle.............................................................................................. 185

16.3.3 Mantle Cavity.............................................................................................................................. 186

16.3.4 Digestive System......................................................................................................................... 188

16.3.5 Renopericardial System............................................................................................................... 189

16.3.6 Reproductive System................................................................................................................... 189

16.3.7 Nervous System and Sense Organs............................................................................................. 189

16.4 Biology and Ecology................................................................................................................................. 190

16.4.1 Habits and Habitats...................................................................................................................... 190

16.4.2 Locomotion.................................................................................................................................. 190

16.4.3 Feeding and Diet.......................................................................................................................... 190

16.4.4 Reproduction, Development, and Growth................................................................................... 192

16.4.5 Associations................................................................................................................................. 192

16.4.6 Predation, Defence, and Other Behavioural Attributes............................................................... 193

16.5 Diversity and Fossil History...................................................................................................................... 193

16.5.1 The Major Groups of Scaphopods............................................................................................... 193

16.6 Human Uses.............................................................................................................................................. 193

Chapter 17 The Cephalopoda................................................................................................................................................. 195

17.1 Introduction............................................................................................................................................... 195

17.2 Phylogeny and Classification....................................................................................................................200

17.3 Morphology............................................................................................................................................... 202

17.3.1 Shell.............................................................................................................................................. 202

17.3.2 Head, Arms, and Funnel.............................................................................................................. 205

17.3.2.1 Embryological Evidence for the Derivation of Head Structures................................. 208

17.3.3 Epidermis (Skin)........................................................................................................................... 208

17.3.4 Head and Funnel Retractor Muscles............................................................................................ 209

17.3.4.1 Muscular Attachments, Shell Growth and the Addition of Septa.................................210

17.3.5 The Fossil Record of Soft Tissues................................................................................................ 212

17.3.6 Mantle Wall.................................................................................................................................. 213

17.3.7 Mantle Cavity................................................................................................................................214

17.4 Biology and Ecology..................................................................................................................................218

17.4.1 Habits and Habitats.......................................................................................................................218

17.4.1.1 The Habits and Habitats of Extinct Ectocochleate Cephalopods.................................218

17.4.2 Locomotion and Buoyancy.......................................................................................................... 220

17.4.2.1 Locomotion................................................................................................................. 220

17.4.2.2 Buoyancy..................................................................................................................... 222

17.4.2.3 The Shell as a Buoyancy Device................................................................................. 222

17.4.2.4 Other Buoyancy Strategies.......................................................................................... 227

17.4.3 The Ink Sac and Inking................................................................................................................ 228

17.4.4 Colour Changes – Chromatophores and Other Special Skin Structures..................................... 228

17.4.4.1 Chromatophores.......................................................................................................... 229

17.4.4.2 Structural Reflectors (Iridophores, Silvery Reflectors, and Leucophores).................. 229

17.4.5 Luminescent Organs.................................................................................................................... 231

17.5 Digestive System....................................................................................................................................... 233

17.5.1 The Jaws....................................................................................................................................... 233

17.5.2 The Radula................................................................................................................................... 233

17.5.3 Feeding......................................................................................................................................... 233

17.6 Renopericardial System............................................................................................................................. 236

17.7 Courtship, Reproduction, Development, and Growth............................................................................... 239

17.7.1 Reproductive System.................................................................................................................... 239

17.7.1.1 Sexual Characters and Sexual Dimorphism................................................................ 242

17.7.2 Courtship and Mating.................................................................................................................. 243

17.7.3 Life History..................................................................................................................................244

17.7.3.1 Spawn and Parental Care............................................................................................. 245

17.7.3.2 Development................................................................................................................ 245

17.7.4 The Nervous System, Sense Organs, and Behaviour................................................................... 247

17.7.5 The Endocrine System................................................................................................................. 249

17.7.6 Learning and Intelligence............................................................................................................ 249

17.7.7 Behaviour..................................................................................................................................... 249

17.7.8 Symbiotic Relationships............................................................................................................... 250

17.7.9 Predators....................................................................................................................................... 251

17.8 Economic Values....................................................................................................................................... 251

17.9 The Origin of Cephalopods....................................................................................................................... 251

17.10 Diversity and Fossil History...................................................................................................................... 256

17.10.1 The Ordovician Radiation and Beyond........................................................................................ 256

17.11 The Major Groups of Cephalopoda........................................................................................................... 258

17.11.1 The Nautiliforms.......................................................................................................................... 258

17.11.1.1 Ellesmeroceratia and Plectronoceratia...................................................................... 259

17.11.1.2 Orthoceratia............................................................................................................... 260

17.11.1.3 Discosorida................................................................................................................ 261

17.11.1.4 Endoceratia................................................................................................................ 261

17.11.1.5 Actinoceratia.............................................................................................................. 261

17.11.1.6 Nautilia...................................................................................................................... 262

17.12 Bactrita and Ammonitia (= Ammonoidea)................................................................................................ 262

17.12.1 Bactrita (= Bactritoidea)............................................................................................................... 262

17.12.2 Ammonitia (Ammonites)............................................................................................................. 264

17.12.2.1 The Embryonic Shell (Ammonitella)........................................................................ 267

17.12.2.2 Ammonite Sutural Patterns........................................................................................ 267

17.12.2.3 Life Habits................................................................................................................. 268

17.12.2.4 Aptychus and Jaws.................................................................................................... 269

17.12.2.5 Phylogeny, Classification, Diversity, and Fossil History of Ammonites................... 271

17.12.2.6 The Major Groups of Ammonites............................................................................. 272

17.13 Coleoida.................................................................................................................................................. 273

17.13.1 Phylogeny, Classification, Diversity, and Fossil History............................................................ 275

17.13.1.1 Belemnitidia (The Belemnites)................................................................................ 279

17.13.1.2 Decabrachia............................................................................................................. 279

17.13.1.3 Squid – A Grade Not a Clade – The Myopsida, Oegopsida, Bathyteuthoidea

(‘Teuthida’) �......................................................................................................... 284

17.13.1.4 Octobrachia (= Octopodiformes)............................................................................. 285

17.13.1.5 Giant Squid and Octopuses...................................................................................... 287

Chapter 18 Gastropoda I – Introduction and the Stem Groups.............................................................................................. 289

18.1 Introduction to the Gastropoda.................................................................................................................. 289

18.1.1 Phylogeny and Classification........................................................................................................ 289

18.1.2 Morphology.................................................................................................................................. 290

18.1.2.1 Shell, Operculum and External Body.......................................................................... 293

18.1.2.2 Shell Muscles.............................................................................................................. 294

18.1.2.3 Operculum................................................................................................................... 294

18.1.2.4 Head-Foot.................................................................................................................... 294

18.1.2.5 Mantle Cavity and Its Organs...................................................................................... 296

18.1.2.6 Digestive System......................................................................................................... 296

18.1.2.7 Renopericardial System............................................................................................... 297

18.1.2.8 Reproductive System...................................................................................................300

18.1.2.9 Nervous System and Sense Organs.............................................................................300

18.1.3 Biology, Ecology, and Behaviour.................................................................................................300

18.1.3.1 Habits and Habitats.....................................................................................................300

18.1.3.2 Locomotion and Behaviour......................................................................................... 301

18.1.3.3 Life History................................................................................................................. 301

18.1.3.4 Feeding........................................................................................................................ 301

18.1.3.5 Associations................................................................................................................. 302

18.1.4 Economic Values.......................................................................................................................... 303

18.1.5 Diversity and Fossil History......................................................................................................... 303

18.2 The Initial Radiation – Eogastropods and Orthogastropods ............................................................ 303

18.2.1 Hypothetical Reconstructions...................................................................................................... 303

18.2.1.1 A Hypothetical Ancestral Gastropod........................................................................... 307

18.2.1.2 Eogastropoda............................................................................................................... 308

18.2.1.3 Orthogastropoda...........................................................................................................310

18.3 The Lower Groups of Gastropods..............................................................................................................312

18.4 Patellogastropoda (= Docoglossa, Cyclobranchia, Eogastropoda in Part).................................................312

18.4.1 Introduction...................................................................................................................................312

18.4.2 Phylogeny and Classification.........................................................................................................312

18.4.2.1 Sister Group Relationships...........................................................................................313

18.4.2.2 Outline of Classification...............................................................................................313

18.4.3 Morphology...................................................................................................................................313

18.4.3.1 Shell and Protoconch....................................................................................................313

18.4.3.2 Head-Foot, Mantle, and Operculum.............................................................................315

18.4.3.3 Mantle Cavity...............................................................................................................315

18.4.3.4 Digestive System..........................................................................................................317

18.4.3.5 Reproductive System................................................................................................... 320

18.4.3.6 Renopericardial System............................................................................................... 320

18.4.3.7 Nervous System and Sense Organs............................................................................. 321

18.4.4 Biology, Ecology, and Behaviour................................................................................................. 322

18.4.4.1 Habits and Habitats..................................................................................................... 322

18.4.4.2 Locomotion and Behaviour......................................................................................... 322

18.4.4.3 Life History................................................................................................................. 322

18.4.4.4 Feeding and Diet......................................................................................................... 322

18.4.4.5 Associations................................................................................................................. 323

18.4.5 Diversity and Fossil History......................................................................................................... 323

18.5 Vetigastropoda........................................................................................................................................... 324

18.5.1 Introduction.................................................................................................................................. 324

18.5.2 Phylogeny and Classification........................................................................................................ 324

18.5.2.1 Outline of Classification.............................................................................................. 326

18.5.2.2 Deep-Sea Enigmas; The Neomphaloidean and Cocculinoidean Taxa........................ 332

18.5.3 Morphology.................................................................................................................................. 333

18.5.3.1 Shell and Protoconch................................................................................................... 333

18.5.3.2 Head-Foot, Mantle, Operculum, and Locomotion...................................................... 337

18.5.3.3 Mantle Cavity.............................................................................................................. 338

18.5.3.4 Digestive System......................................................................................................... 338

18.5.3.5 Reproductive System................................................................................................... 343

18.5.3.6 Renopericardial System............................................................................................... 344

18.5.3.7 Nervous System and Sense Organs............................................................................. 344

18.5.4 Biology, Ecology, and Behaviour................................................................................................. 345

18.5.4.1 Habits and Habitats..................................................................................................... 345

18.5.4.2 Feeding and Diet......................................................................................................... 345

18.5.4.3 Life History................................................................................................................. 346

18.5.4.4 Associations................................................................................................................. 346

18.5.4.5 Behaviour.................................................................................................................... 346

18.5.5 Diversity and Fossil History......................................................................................................... 346

18.6 Neritimorpha (= Neritopsina).................................................................................................................... 347

18.6.1 Introduction.................................................................................................................................. 347

18.6.2 Phylogeny and Classification........................................................................................................ 347

18.6.2.1 Sister Group Relationships.......................................................................................... 349

18.6.2.2 Outline of Classification.............................................................................................. 349

18.6.3 Morphology.................................................................................................................................. 350

18.6.3.1 Shell and Protoconch................................................................................................... 350

18.6.3.2 Head-Foot, Mantle, Operculum, and Locomotion.......................................................351

18.6.3.3 Mantle Cavity.............................................................................................................. 353

18.6.3.4 Digestive System......................................................................................................... 354

18.6.3.5 Renopericardial System............................................................................................... 355

18.6.3.6 Reproductive System................................................................................................... 355

18.6.3.7 Nervous System and Sense Organs............................................................................. 360

18.6.4 Biology and Ecology.................................................................................................................... 360

18.6.4.1 Habits and Habitats..................................................................................................... 360

18.6.4.2 Feeding and Diet......................................................................................................... 361

18.6.4.3 Life History................................................................................................................. 361

18.6.4.4 Associations................................................................................................................. 362

18.6.4.5 Behaviour.................................................................................................................... 362

18.6.5 Diversity and Fossil History......................................................................................................... 363

Chapter 19 Gastropoda II – The Caenogastropoda................................................................................................................ 365

19.1 Introduction............................................................................................................................................... 365

19.2 Phylogeny and Classification.................................................................................................................... 365

19.2.1 Sister Group Relationships........................................................................................................... 365

19.2.2 Outline of Classification............................................................................................................... 365

19.3 Morphology............................................................................................................................................... 366

19.3.1 Shell and Protoconch.................................................................................................................... 377

19.3.2 Head-Foot, Mantle, and Operculum............................................................................................ 379

19.3.2.1 Head Structures........................................................................................................... 379

19.3.2.2 The Foot...................................................................................................................... 379

19.3.2.3 The Operculum............................................................................................................ 380

19.3.2.4 Mantle Edge................................................................................................................ 380

19.3.3 Mantle Cavity............................................................................................................................... 380

19.3.4 Digestive System.......................................................................................................................... 381

19.3.5 Renopericardial System............................................................................................................... 394

19.3.6 Reproductive System.................................................................................................................... 394

19.3.6.1 The Female System..................................................................................................... 395

19.3.6.2 The Male System......................................................................................................... 396

19.3.7 Nervous System and Sense Organs..............................................................................................400

19.4 Biology, Ecology, and Behaviour.............................................................................................................. 403

19.4.1 Habits and Habitats...................................................................................................................... 403

19.4.2 Locomotion.................................................................................................................................. 403

19.4.3 Feeding and Diet..........................................................................................................................404

19.4.4 Life History and Growth.............................................................................................................. 405

19.4.4.1 Spawn, Development, and Larvae............................................................................... 405

19.4.5 Associations..................................................................................................................................410

19.4.5.1 The Evolution of Parasitism in Eulimidae....................................................................410

19.4.6 Predators and Defence..................................................................................................................412

19.4.7 Other Behavioural Attributes........................................................................................................412

19.5 Economic and Ecological Values...............................................................................................................412

19.6 Diversity and Fossil History.......................................................................................................................413

19.7 Major Groups within Caenogastropoda.....................................................................................................414

19.7.1 The Architaenioglossans...............................................................................................................414

19.7.1.1 Campanilida.................................................................................................................415

19.7.2 Sorbeoconcha................................................................................................................................415

19.7.2.1 Cerithiimorpha.............................................................................................................415

19.7.2.2 Hypsogastropoda..........................................................................................................416

Chapter 20 Gastropoda III – The Heterobranchia...................................................................................................................419

20.1 Introduction................................................................................................................................................419

20.2 Phylogeny and Classification.....................................................................................................................419

20.2.1 Sister Group Relationships........................................................................................................... 421

20.2.2 Chromosome Numbers................................................................................................................. 422

20.3 Morphology............................................................................................................................................... 429

20.3.1 Shell and Operculum.................................................................................................................... 435

20.3.1.1 Shell Structure............................................................................................................. 439

20.3.1.2 Larval or Embryonic Shell.......................................................................................... 439

20.3.1.3 Shell Reduction and Loss............................................................................................ 439

20.3.1.4 Shell Variation.............................................................................................................440

20.3.1.5 Operculum...................................................................................................................440

20.3.2 External Body Morphology.......................................................................................................... 441

20.3.2.1 Head Tentacles............................................................................................................ 441

20.3.2.2 Cephalic (Head) Shield............................................................................................... 442

20.3.2.3 Epithelial Modifications.............................................................................................. 442

20.3.2.4 Oral Veil.......................................................................................................................444

20.3.2.5 The Foot, Pedal Glands, and Parapodia.......................................................................444

20.3.2.6 The Mantle.................................................................................................................. 445

20.3.3 Mantle Cavity and Associated Structures.................................................................................... 447

20.3.3.1 Heterobranch Gills...................................................................................................... 450

20.3.3.2 Opposed Ciliary Ridges (Raphes) and Mantle Tentacles............................................ 451

20.3.3.3 The Hypobranchial Gland........................................................................................... 451

20.3.3.4 The Pigmented Mantle Organ (PMO)......................................................................... 452

20.3.3.5 Other Glands Associated with the Mantle Cavity....................................................... 452

20.3.4 Digestive System.......................................................................................................................... 452

20.3.5 The Renopericardial System........................................................................................................ 472

20.3.6 Nervous System and Sense Organs.............................................................................................. 474

20.3.6.1 Sense Organs............................................................................................................... 477

20.3.7 Reproductive System.................................................................................................................... 479

20.3.7.1 Terminology................................................................................................................ 479

20.3.7.2 The Ovotestis and Gametes......................................................................................... 481

20.3.7.3 The Reproductive System of ‘Lower Heterobranchs’................................................. 482

20.3.7.4 Some Small Euthyneurans Previously Thought to Be Lower Heterobranchs............. 485

20.3.7.5 Euthyneuran Reproductive Systems............................................................................ 486

20.4 Biology, Ecology, and Behaviour.............................................................................................................. 503

20.4.1 Habits and Habitats...................................................................................................................... 503

20.4.2 Locomotion.................................................................................................................................. 503

20.4.3 Food and Feeding......................................................................................................................... 504

20.4.3.1 Herbivory..................................................................................................................... 505

20.4.3.2 Fungivory.................................................................................................................... 505

20.4.3.3 Active Carnivory.......................................................................................................... 505

20.4.3.4 Parasitism.................................................................................................................... 507

20.4.3.5 Suspension Feeding..................................................................................................... 507

20.4.3.6 Coprophagy................................................................................................................. 507

20.4.4 Reproduction, Development, and Growth.................................................................................... 507

20.4.4.1 Self-Fertilisation.......................................................................................................... 508

20.4.4.2 Hypodermic Insemination........................................................................................... 508

20.4.4.3 Aphally........................................................................................................................ 508

20.4.4.4 Asexual Reproduction................................................................................................. 509

20.4.4.5 Life Cycles.................................................................................................................. 509

20.4.4.6 Reproductive Behaviour.............................................................................................. 509

20.4.4.7 Development................................................................................................................ 509

20.4.4.8 Spawn...........................................................................................................................510

20.4.4.9 Larvae and Larval Shells..............................................................................................514

20.4.5 Behaviour..................................................................................................................................... 515

20.4.6 Predation and Defence................................................................................................................. 515

20.4.6.1 The Shell as a Means of Defence................................................................................ 515

20.4.6.2 Mucus...........................................................................................................................516

20.4.6.3 Defence without a Shell...............................................................................................516

20.4.6.4 Use of Nematocysts......................................................................................................517

20.4.6.5 Aposematic (Warning) Colouration and Batesian and Müllerian Mimicry.................518

20.4.6.6 Autotomy......................................................................................................................519

20.4.6.7 Predators of Heterobranchs..........................................................................................519

20.4.7 Associations................................................................................................................................. 520

20.4.8 Economic and Ecological Values................................................................................................. 520

20.5 Diversity and Fossil History...................................................................................................................... 520

20.5.1 Major Groups within the Heterobranchia.................................................................................... 521

20.5.1.1 ‘Lower Heterobranchs’................................................................................................ 521

20.5.1.2 Euthyneura.................................................................................................................. 521

Chapter 21 Molluscan Research – Present and Future Directions......................................................................................... 527

21.1 Molluscan Research Publications.............................................................................................................. 527

21.1.1 Provision of Basic Information.................................................................................................... 527

21.1.1.1 Use of Museum Collections........................................................................................ 529

21.1.1.2 Research Workshops................................................................................................... 529

21.1.1.3 DNA Barcoding........................................................................................................... 529

21.1.1.4 Genetics....................................................................................................................... 529

21.2 Palaeobiology............................................................................................................................................ 530

21.3 Taphonomy.................................................................................................................................................531

21.4 Systematics................................................................................................................................................ 532

21.5 Systematic, Phylogenetic, and Evolutionary Studies................................................................................ 532

21.5.1 Different Datasets......................................................................................................................... 532

21.5.1.1 Molecular Datasets...................................................................................................... 533

21.6 Biogeography............................................................................................................................................ 535

21.7 Discovery................................................................................................................................................... 535

21.8 The Future................................................................................................................................................. 535

21.8.1 Text Mining.................................................................................................................................. 536

21.8.2 New Technology........................................................................................................................... 536

21.8.3 Phylogenetic and Evolutionary Research..................................................................................... 536

21.8.4 Biodiversity.................................................................................................................................. 538

21.8.5 Citizen Science............................................................................................................................. 540

Appendix

Higher Classification of the Extant Classes of Mollusca..................................................................................... 543

References................................................................................................................................................................................. 725

Index...........................................................................................................................................................................................817