The parade of the Craniates Part 1
Dec 17, 2015
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