Ulf J. Borgen & Hans A. Nakrem 
Morphology, Phylogeny and Taxonomy of Osteolepiform Fish 

A discussion and description of prehistoric fish within an international series Material of six osteolepiform genera is described in Morphology, Phylogeny and Taxonomy of Osteolepiform Fish. This publication is Number 61 within the Fossils and Strata series. The international Fossils and Strata series features monographs in palaeontology and biostratigraphy with taxonomic descriptions. The series is owned by and published on behalf of The Lethaia Foundation in cooperation with the Scandinavian countries.

Inhaltsverzeichnis

Introduction 1

General taxonomy 2

‚Crossoptgerygii‘ and ‚Rhipidistia‘ 2

Osteolepiform subdivisions 3

Terminology 4

Cranial roof 4

Endocranium 13

Dermal bones in mouth roof 13

Lower jaw 14

Operculo-gular bones 15

Upper Palaeozoic fossil locality in the Oslo Region 16

Stratigraphy 16

Descriptions 18

Material, methods and repository 18

Genus Askerichthys n gen 20

Askerichthys heintzi n sp 20

Genus Megalichthys Agassiz, 1835 62

Megalichthys cf M hibberti Agassiz, 1835 62

Megalichthys pygmaeus Tranquair, 1879 97

Megalichthys syndentolaminaris n sp 99

Genus Latvius Jarvik, 1948 100

Latvius grewingki (Gross, 1933) 101

Latvius deckerti Jensen, 1966 114

Latvius sp Jensen, 1966 121

Latvius cf L niger Jensen, 1973 128

Genus Osteolepis Agassiz, 1835 130

Osteolepis macrolepidotus Agassiz, 1835 131

Genus Gyroptychius Mc Coy, 1848 131

Gyroptychius milleri (Jarvik, 1948) 131

Gyroptychius groenlandicus Jarvik, 1950a 141

Morphologic comparisons and discussions 160

Fronto-ethmoidal shield 160

General shape 160

Interpremaxilla 162

Composition of naso-rostro-premaxillary complex 162

Shape of upper mouth margin 165

Anterior palatal (premaxillary and rostral) teeth and palatal processes 166

Defi nitions and occurrences of morphotypes of anterior palatal teeth 166

Tooth replacement and evolutionary relationship between the anterior palatal dental morphotypes 167

Number of premaxillary teeth 169

Systematic significance of anterior palatal teeth 170

Anterior palatal processes 171

Postrostrals 172

Variation and trends in postrostral pattern 172

Taxonomic significance of postrostral pattern 176

Nasals 178

Number of nasal bones 178

Positions of the bones in the nasal series 178

Circumnarial dermal bones and supraorbitals 180

Variation in eusthenopterids 180

Reconstructing the circumnarial pattern in Osteolepis macrolepidotus 186

Reconstructing the pattern of supraorbitals in Osteolepis macrolepidotus 188

Circumnarial and supraorbital pattern in other Devonian osteolepiforms 189

Homologizations of circumnarial bones in Megalichthys hibberti, Ectosteorhachis, Askerichthys and Cladarosymblema 191

Supraorbito-tectal series of panderichthyids 196

Frontals and dermosphenotics 197

Shape and composition of frontals 197

Shape, positions and extension of dermosphenotic bones 199

Fenestrae 199

Position of nasal fenestra 199

Shape of nasal fenestra 200

Processus dermintermedius 201

Tubercles in nasal fenestra 202

Presence or absence of pineal openings 202

Position of pineal foramen 203

Shape of pineal openings 204

Size of pineal fenestra and presence of pineal plates 204

Sensory canals 204

Pitlines 205

Parietal shield 206

Relative lengths of fronto-ethmoidal and parietal shields 206

Shape of parietal shield 207

Proportions 207

Protruding posterior margin 209

Position of spiracular incision 212

Relative length of the spiracular incision 213

Parietals 214

Shape of parietals 214

Parietal structures 214

Intertemporals 215

Shape of interpemporal 215

Anterior intertemporal margin and process in post-Devonian taxa 216

Anterior intertemporal processes in Devonian forms 222

On the function of the intracranial joint 223

Lateral shelf of intertemporal 223

Ventral surface of intertemporal 224

Supratemporals 228

Shape 228

Ventral surface and lateral margin 228

Spiracular structures 231

Extension of the spiracular opening 231

Types of spiracular openings 232

Possible muscle insertions around the spiraculum 233

Extratemporal (= postspiraculars) 236

Sensory canals 236

Course of sensory canal 236

Position of canal openings 237

Pitlines 238

Extrascapulars238

Dermal palatal bones 239

Vomers 239

Review of taxa with known vomers 239

Transverse tusk positions on anterior vomers 243

Configuration of anterior vomers 244

Extensions and proportions of the posterior vomer 245

Dental lamina and teeth 245

Intervomerine Canals 246

Evolution of the vomers 247

Parasphenoid 248

Division of the parasphenoid 248

Paraspenoid dental plate 248

Buccohypophysial foramen 250

Pars anterior of parasphenoid 250

Parasphenoid shelves and processi ascendens 250

Foramina on the shelf 253

Acrochordal depressions, additional dermal bones and basicranial muscles 254

Occurrence of acrochordal depressions 254

Function of acrochordal depressions 255

Endocranium 258

Ethmosphenoid 258

Proportions of ethmosphenoid 258

Subethmoidal fossae 258

Nasobasal canal and palatonasal canal 261

Internal structures of nasal capsule 261

Postnasal wall 263

Orbitosphenoid wall of eusthenopterids 268

Comparing orbitosphenoid region of Ectosteorhachis foordi with other cyclolepidoids than eusthenopterids 271

Orbitosphenoid in Osteolepidoidei and other forms 273

Systematic significance of orbitosphenoid structure 277

Posterior end of orbitosphenoid 277

Otico-occipital 278

Cheek plate 280

Maxilla 280

Shape 280

Ventral margin and tooth distribution on maxilla 282

Postorbital and squamosal 283

Lachrymal 285

Jugal 285

Shape 285

Contact with the orbit 285

Quadratojugal 287

Lower jaw (= mandible) 287

Shape 287

Proportions 287

Anterior notch 288

Antero-dorsal bulb 288

Dorsal margin 288

Positions of dental margin and glenoid notch 290

Retroarticular process 292

External structures 292

Dentary/Infradentary suture 292

Inter-infradentary sutures 294

Dorsal cosmine notch, cosmine corners and postero-dorsal bone margin 295

Horizontal pitline 298

Vertical pitline of infradentary 2 300

Sensory canal 300

Canal course 301

Configuration of canals 301

Dentary 302

Dentary teeth 302

Dentary shelf and dental fossa 307

Coronoids 307

Number of coronoid bones and tusks 307

Replacement of coronoid tusks 312

Relative size of coronoid tusks 313

Relative positions of coronoid tusks 315

Coronoid dental ridge 317

Intercoronoid fossae 321

Anterior mandibular fossa 322

Prearticular 322

Presence of a pars anterior of the prearticular 322

Anteriad extension and configuration of pars anterior of the prearticular 323

Course of the pars anterior of the prearticular 329

Anterior extension of prearticular dental plate 330

Shape of dental plate 331

Prearticular dental plate configuration and teeth 332

Postero-ventral depression 332

Posterior part of prearticular 333

Parasymphyseal dental plate and adsymphysial fossa 333

Occurrence of Parasymphyseal dental plate 333

Shape of Parasymphyseal dental plate 334

Relations of Parasymphyseal dental plate to other bones 334

Adsymphysial fossa 338

Infradentaries 341

Infradentary surfaces 341

Posterior extension of infradentaries 341

Meckelian bone 342

Pars mentomandibularis 342

Ventral exposures 342

Pars articularis 342

Foramina 343

Sensory canal foramina 343

Foramina for nerves and vessels 344

Sensory canal pore patterns 350

Distribution patterns of sensory pores 350

Pore distribution as an age indicator 350

Evolution of pore dispersion 353

Taxonomic significance of pore number and distribution 355

Size and types of sensory pits 357

Operculo-gular complex 357

Median gular 357

Principal gulars 360

Submandibulars 362

Opercular and subopercular 365

Shoulder girdle 367

Scapulocoracoid 367

Dermal shoulder girdle 368

Fins 369

Caudal fin 369

Position of fins 370

Scales, body proportions and vertebrae 370

Scales 370

Scale distribution 370

Scale morphology 371

Body proportions 371

Vertebrae 371

Phylogeny and taxonomy of osteolepiforms 372

Taxonomic concepts and principles 372

Characters 372

Quantitative characters 372

Primitive and derived characters, convergence, parallelism and homoplasy 372

Sufficient, necessary, indicative, single and combined characters 375

Diagnoses 376

A phylogenetic model 377

A systematic model 381

Order Osteolepiformes Berg, 1937 381

Suborder Osteolepidoidei Moy-Thomas & Miles, 1971 382

Family Thursiidae n fam 383

Genus Thursius Traquair, 1888 384

Family Osteolepididae Cope, 1889 388

Subfamily Glyptopominae Goodrich, 1909 389

Genus Glyptopomus Agassiz, 1844 390

Genus Megistolepis Obruchev, 1955 392

Genus Shirolepis Vorobyeva, 1977a 393

Genus Greiserolepis Vorobyeva, 1977a 394

Subfamily Osteolepidinae n subfam 396

Genus Osteolepis Agassiz, 1835 396

Genus Latvius Jarvik, 1948 397

Genus Gogonasus Long, 1985b 400

Genus Geptolepis Vorobyeva & Lebedev, 1986a 403

Genus Peregrina Vorobyeva & Lebedev, 1986b 404

Family Megalichthyidae Hay, 1902 406

Subfamily Ectosteorhachinae n subfam 412

Genus Ectosteorhachis Cope, 1880 412

Subfamily Megalichthyinae n subfam or Cope, 1940 415

Genus Cladarosymblema Fox, Cambell, Barwick & Long, 1995 415

Genus Megalichthys Agassiz, 1835 415

Subfamily Askerichthyinae n subfam 419

Genus Askerichthys n gen 419

Suborder Cyclolepidoidei n suborder 420

Superfamily Eopodoidea n superfam 420

Family Gyroptychiidae Berg, 1958 Berg 1940 422

Genus Gyroptychius Mc Coy, 1848 422

Family Panderichthyidae Vorobyeva & Lyarskaya, 1968 429

Subfamily Panderichthyinae n subfam 432

Genus Panderichthys Gross, 1941 432

Genus Livoniana Ahlberg, Lukseviès & Lebedev, 2000 435

Subfamily Elpistosteginae n subfam 435

Genus Elpistostege Westoll, 1938 436

Genus Tiktaalik Daeschler, Shubin & Jenkins, 2006 436

Family Chrysolepididae n fam 438

Genus Chrysolepis Lebelev, 1983 438

Family Eusthenopteridae Berg, 1955 440

Genus Tristichopterus Egerton, 1861 445

Genus Eusthenopteron Whiteaves, 1881 447

Genus Eusthenodon Jarvik, 1952 448

Genus Platycephalichthys Vorobyeva, 1959 449

Genus Jarvikina Vorobyeva, 1977a 452

Genus Marsdenichthys Long, 1985a 453

Genus Spodichthys Jarvik, 1985 455

Genus Notorhizodon Young, Long, & Ritchie, 1992 456

Genus Mandageria Johanson & Ahlberg, 1997 457

Genus Cabonnichthys Ahlberg & Johanson, 1997 458

Genus Heddleichthys Snitting, 2008b 460

Genus Langlieria Clément, Snitting & Ahlberg, 2008 462

Superfamily Parapodoidea n superfam 463

Family Medoevididae n fam 463

Genus Medoevia Lebedev, 1995 463

Family Canowindridae Young, Long & Ritchie, 1992 464

Genus Canowindra Th omson, 1973 465

Genus Beelarongia Long, 1987 466

Genus Koharalepis Young, Long & Ritchie, 1992 467

Superfamily Rhizodontoidea n superfam 468

Osteolepiformes subord indet 468

Family Lamprotolepididae Vorobyeva, 1977a 468

Genus Lamprotolepis Vorobyeva, 1977a 468

Osteolepiformes subord & fam indet 470

Genus Litoptychius Denison, 1951 470

Genus Lohsania Thomson & Vaughn, 1968 471

Genus Sterropterygion Thomson, 1972 472

Genus Megapomus Vorobyeva, 1977a 472

Genus Thysanolepis Vorobyeva, 1977a 474

Genus Viluichthys Vorobyeva, 1977a 475

Genus Mahalalepis Young, Long & Ritchie, 1992 476

Genus Platyethmoidea Young, Long & Ritchie, 1992 478

Genus Vorobjevaia Young, Long & Ritchie, 1992 479

Genus Sengoerichthys Janvier, Clément & Cloutier, 2007 480

Genus Criptolepis Worobjeva, 1975c 481

Acknowledgements 481

References 482

Tables 491

Appendix Abbreviations used in illustrations and tables 506

Über den Autor

Ulf J. Borgen is the editor of Morphology, Phylogeny and Taxonomy of Osteolepiform Fish, published by Wiley.

Hans A. Nakrem is the editor of Morphology, Phylogeny and Taxonomy of Osteolepiform Fish, published by Wiley.