The parade of the Craniates

Part 1

Major synapomorphies of the Craniates

1. Developmental• Neural crest• Neurogenic placodes

2. Nervous System• Above• Braincase (skeletal)• Complex sense

organs• Cranial nerves• Tripartite brain

3. Endocrine system is complex

4. Gut• Muscularization• Regionalization• Differentiated organs

5. Cardiovascular• Gills• Heart• Hemoglobin

Craniate phylogenyand diversity of living species

Fig. 3.1

Agnathans

• Jawless

• Include:– Ostracoderms– Hagfishes and lampreys

Ostracoderms

• Extinct

• “Armored” – bony dermis

• Middle Ordovician (maybe Cambrian)

• Most lacked paired fins

• Length 2-3cm to 2-2.5m

• Heterocercal tail

• Ostracoderms

Hagfish and Lampreys

• Hagfish– Marine– Scavengers

• Lamprey– Anadromous– Buccal funnel– Parasitic– Historically conservative anatomy (Carboniferous)

Gnathostomes

• Paleozoic– Placoderms– Chondrichthyans– Teleostomes

• Acanthoidians• Ostichthyans

Ost

raco

derm

s

jaws

Placoderms

• Devonian (~400mya)

• Paired p. and p. fins

• Jointed, bony shields

Chondrichthyes• Cartilaginous skeleton• Bones in scales and teeth

– Elasmobranchs (sharks, skates, rays,sawfishes)

• Naked gill slits (cf. bony fish operculum)• spiracle• Heterocercal tail morphology

– Holocephalans (Chimaeras (ratfish))• Scales reduced to absent• Upper jaw continuous with braincase• Fleshy operculum• Bony plates instead of teeth

Squaliformes - sharks

• Lateral gill slits

Rajiformes – skates, rays, sawfishes

• Ventral gill slits

Holocephalans

• Upper jaw connected to braincase

Acanthodians and Osteichthyans

• Acanthodians– Extinct– Hollow spines in paired fins– Bony armor

Osteichthyans

• The extant bony fish– Bony skeleton– Airsac– Paired appendages (fins)

– Actinopterygii – ray-finned fishes• Basal actinopterygians (sturgeons, paddlefishes, Polypterus)• Neopterygians (gars, bowfins, teleost fishes)

– Sarcopterygii – lobe-finned fishes• Actinistians – coelacanths• Rhipidistians – lungfishes

Basal Actinopterygians

Neopterygii

Ganoid scale

Neopterygians

Teleosts (23,000 species)

Bowfin

Gar

Sarcopterygians

Tetrapods

Coelocanths (Actinistians)

Lungfishes (Rhipidistians)

The parade of the craniates

Part 2

Tetrapoda