IV' Basal Groups of Gnathostomes

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IV. Basal Groups of Gnathostomes
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A. Placoderms, chondrichthyans teleostomes are
gnathostomes
1. Synapomorphies of gnathostomes
a. Three semicircular ducts in the inner ear
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b. Articulated gill arches, each primitively
consisting of five subunits
Fig. 7.3
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c. Jaws review evolution of vertebrate jaws and
jaw suspension
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B. Basic facts about Placoderms
1. Dominant Devonian fishes in diversity,
habitat, and body size 2. Heavily armored head,
less armored body 3. Often have cutting tooth
plates 4. Many have unusual neck joint between
plates of head and trunk 5. Monophyletic?
usually thought to be, but little is known 6.
Much uncertainty about higher systematic
relationships
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Coccosteus
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Coccosteus
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Dunkelosteus
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Dunkelosteus
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Bothriolepis
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Bothriolepis
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Cladoselache
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Heterodontiformes Bullhead Sharks 1 family, 1
genus, 8 species. a. Family Heterodontidae
Bullhead or Port Jackson Sharks 1 genus, 8
species. (1) small sharks (2) distinctive
teeth (3) leading fin spines on both dorsal
fins (4) oviparous (5) Heterodontus
portusjacksoni
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Heterodontus francisci
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Orectolobiformes Carpet Sharks 7 families, 14
genera, 31 species. a) small to gigantic b) two
dorsal fins, no spines c) oviparous d) Family
Orectolobidae Wobbegons 3 genera, 6
species. (1) Orectolobus Australian
Wobbegons e) Family Ginglymostomatidae Nurse
Sharks 3 genera, 3 species. (1) Ginglymostoma
cirratum Nurse Shark f) Family Rhincodontidae
Whale Sharks 1 species (1) Rhincodon typus
Whale shark 12m, possibly 18m
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Lamniformes Mackerel Sharks 7 families, 10
genera, 16 species. A. Family Odontaspidae
Sand Tiger Sharks 2 genera, 4 species 1)
Odontaspis taurus Sand Tiger B. Family
Megachasmidae Megamouth Shark 1 species 1)
Megachasma to 5.1m TL C. Family Alopiidae
Thresher Sharks 1 genus, 5 species 1) Alopias
distinctive sickle-shaped tail used to stun
prey D. Family Cetorhinidae Basking Shark 1
species 1) Cetorhinus maximus up to 15m
TL E. Family Lamnidae Mackerel Sharks 3
genera, 5 species 1) Carcharodon carcharias
White Shark 2) Isurus Makos two species in
our area 3) Lamna nasus Porbeagle
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Fig. 3.7
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Fig. 3.7
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Carchariniformes Ground Sharks 7 families, 47
genera, 208 species. A. Family Scyliorhinidae
Cat Sharks 15 genera, 96 species (1)
Scyliorhinus retifer Chain Dogfish B. Family
Triakidae Hound Sharks 9 genera, 39
species (1) Triakis maculata Leopard Sharks
California Coast (2) Mustelus canis Smooth
Dogfish to 1.5m TL C. Family Carcharhinidae
Requiem Sharks 13 genera, 58 species (1)
Carcharhinus Whaler Sharks C. leucas Bull
Shark C. mibatus Blacktip Shark (2)
Negaprion brevirostris Lemon Shark (3)
Rhizoprionodon terraenovae Atlantic
Sharpnose (4) Galeocerdo cuvieri Tiger
Shark (5) Prionace glauca Blue Shark (6)
Sphyrna Hammerhead Sharks S. zygaena
Smooth or Common Hammerhead S. tiburio
Bonnethead Shark to 1.5m TL
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Peter Forey and a 490 lb female bull shark
Photograph by David McClain, Aurora-Quanta, Inc.
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Carcharhinidae 20 Atlantic Sharpnose
Shark Rhizoprionodon terraenovae WEB 02-385 760
mm TL
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Hexanchiformes Frill Cow Sharks 2 families,
4 genera, 5 species. A. Family
Chlamydoselachidae Frill Shark 1 species (1)
Chlamydoselachus anguineus Frill Shark B.
Family Hexanchidae Cow Sharks 3 genera, 4
species (1) Hexanchus Sixgill Sharks San
Francisco Bay (2) Heptranchias Sevengill
Sharks
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Squaliformes Spiny Dogfish kin 4 families,
23 genera, 74 species. A. Family Dalatiidae
Sleeper Sharks 18 genera, 49 species (1)
Isistius cookie-cutter sharks B. Family
Squalidae Spiny Dogfishes 2 genera, 10
species (2) Squalus acanthias Spiny Dogfish
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Fig. 12.11
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Fig. 12.12
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Fig. 12.8
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Fig. 12.9
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Squatiniformes Angel Sharks 1 family, 1
genus, 12 species. A. Squatinidae (1) Squatina
distinct Atlantic and Pacific species S.
dumerili Atlantic Angel Shark
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Pristiophoriformes Saw Sharks 1 family, 2
genera, 5 species. A. Pristiophoridae
primarily tropical and Indo-Pacific (1) the two
genera differ in number of gill slits
Pristiophorus has 5 Pliotrema has 6.
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