The Diversity of Cartilaginous and other Fishes

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The Diversity of Cartilaginous (and other) Fishes

• P. R. Last

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Presentation themes

• Classification of cartilaginous fishes
• Diversity of major groups
• Taxonomic impediments
• Levels of faunal resolution within groups
• Overview of other fish groups
• Perspectives on the biogeographic framework
• Practical challenges for the Barcode project

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Cartilaginous fishes (Chondrichthyes)?
Sharks (Selachians) Rays (Batoids)
Elasmobranchii

• Holocephali Chimaeras

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Diversity of chondrichthyans

• Sharks 490 105 4.7
• Rays 624 73 8.5
• Chimaeras 48 6 8.0
• Total 1162 184 7.1

Species
Genera
Spp/Genus
Based Compagno, Last, McEachran, Seret,
unpubl 2003
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What is the real magnitude of the task?

• Sharks 490 170 105
• Rays 624 200 73
• Chimaeras 48 20 6
• Total 1162 390 184

Species
Genera
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Specific difficulties associated with
elasmobranch taxonomy?

• THEY ARE BIG!
• types lost or never assigned
• no locality data
• condition of types (old, skins only, fragmented,
  broken)
• types often not transportable
• storage of other large specimens (series!)
• reluctance of museums to send material
• hence, mostly poorly represented in collections
• collections scattered
• nomenclatural issues

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MAJOR SHARK SUBGROUPS
280 117 20 9 6 15 34 9
N 490
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ORDER CARCHARHINIFORMES. GROUND SHARKS.
156 48 4 6 1 8 49 8
N 280
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ORDER SQUALIFORMES. DOGFISHES.
50 19 16 19 6 5 2
N 117
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Apristurus

• ca 45 spp
• Mixed widespread restricted spp
• Species complexes
• Several genera!
• Partitioned by depth
• Need intraregional evaluations

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Centrophorus

• 14 spp
• Possibly the most taxonomically confused shark
  genus
• uyato granulosus complexes
• Material shortage/shrinkage!
• Species vary -
• vertebral counts
• head fin morphology
• dorsal-fin colour
• CO1 looks promising

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Cephaloscyllium

• 18 spp
• Diverse - on upper slopes
• Mainly narrow-ranging endemics
• Many spp undescribed

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Squalus

• 16 spp
• Confused - similar to Centrophorus
• Regional speciation
• mitsukurii complex
• megalops HF group
• Value of juvenile coloration
• Benefits of intraregional studies (Australian
  experience)

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S. cf mitsukurii var E
S. cf mitsukurii var WA

• Australian Squalus phenogram
• (dogfish group)

S. sp. E
S. sp. F
S. sp. D
S. sp. C (HF grp)
-----------0.01 distance
S. sp. B (HF grp)
S. acanthias
S. megalops
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Etmopterus

• 40 spp
• Considered widespread!
• Partitioned on mid-slope
• Species complexes
• lucifer group
• granulosus group
• We may get surprises!

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Sleepers!

• Galeus gracilis and
• G. sp. nov.

Squatina (20 spp)
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MAJOR BATOID SUBGROUPS
292 74 195 44 7 1 6 3 2
N 624
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SUBORDER RAJOIDEI. SKATES.
174 95 23
N 292
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Dipturus

• 52 spp
• Most widely distributed genus
• Many endemic some very restricted
• Stenobathic - important biomic indicators
• Not monophyletic - several supraspecific taxa!

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Notoraja

• 20 spp
• Species complexes in IWP
• Morphologically similar
• Some new genera
• Further collecting needed

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Bathyraja

• 50 spp
• Mainly antitropical
• Spp morphologically variable
• Other supraspecific taxa?
• Few wide-ranging
• (ie B. richardsoni)?

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Anacanthobatis

• 24 spp
• Poorly known and taxonomically confused
• Lumping and splitting
• Lots of names in some regions (certainly
  synonyms)
• .... but several new spp!

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Monotypic families(Hexatrygon and Plesiobatis)

• Tropical deepwater species
• Both assumed widespread
• Morphological work inconclusive
• Molecular studies needed

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Lampreys hagfishes (Agnatha)

• Class Myxini
• Order Myxiniformes
• Myxinidae (hagfishes) 28 spp?
• Class Cephalaspidomorphi
• Order Petromyzontiformes
• Petromyzontidae (lampreys) 14 spp?

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Coelacanths Lungfishes (Sarcopterygii )

• Order Coelacanthiformes
• Latimeriidae (coelacanths) 2 spp
• Order Ceratodontiformes
• Ceratodontidae (Australian lungfishes) 1 sp
• Order Lepidosireniformes
• Lepidosirenidae (South American lungfishes) 1 sp
• Protopteridae (African lungfishes) 4 spp

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Biogeographic considerations

• Are elasmobranch faunas of similar size and
  composition across oceans?
• Does spatial structure vary within and between
  regions?
• What are the respective levels of micro-endemism?

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Comparison of regional faunas
Philippines
Gulf of Mexico
NW Australia
N 164
N 94
N 178
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Intraregional comparison - within the
Australasian region
INDO
INDO
NC
NW
NE
NC
Last Seret, 1999
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Intaregional structure - often complex
Ind
E
Pac
INDO
Ind
NC
E
E
E
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The task some practical challenges

• Securing material of deepwater, elusive and rare
  species
• Infill of faunal survey gaps - often speciose
  with high levels of micro-endemism
• These surveys often costly, particularly from
  deepwater
• Storage of large voucher specimens (images alone
  often inadequate)
• Protocols for linking types/names to OTUs
  identified
• QA - maintaining data quality assurance!