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Class Myxini Order Myxiniformes Family Myxinidae (Hagfishes)

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Class Myxini Order Myxiniformes Family Myxinidae (Hagfishes) Class Myxini Order Myxiniformes Family Myxinidae (hagfishes) • Lacks jaws • Mouth not disk-like • barbels present • Unpaired fins as continuous fin-fold • Branchial skeleton not well developed • Eyes degenerate • 70-200 slime glands • Isoosmotic, simple kidneys, stenohayline, marine • Four rudimentary hearts • No true stomach • Unpaired gonads Class Petromyzontida Order Petromyzontiformes Family Petromyzontidae Class Myxini Order Myxiniformes Family Myxinidae (hagfishes) (Northern Lampreys) • Knot-tying behavior • 8 genera, 34 species • Scavengers • Dorsal fins continuous in • Rely heavily on cutaneous respiration adults • Global, deep sea distribution • Oral disc • Commercial interest – eelskin • 7 pairs of gill openings • Single nostril • Pineal body opening • No bone • No scales • No paired fins • No jaws 1 Class Petromyzontida Order Petromyzontiformes Family Petromyzontidae Class Petromyzontida Order Petromyzontiformes Family Petromyzontidae (Northern Lampreys) (Northern Lampreys) • Anadramous and freshwater • Ammocoete • Parasitic forms: – Non-parasitic forms often • Non-parasitic: freshwater – Parasitic forms often anadramous • Life history Class Conodonta, Conodonts Class Pteraspidiomorphi • Extinct, late Triassic • Extinct • First “teeth” • One of the earliest known vertebrates • No jaws • Dermal skeleton • Cranium and teeth • No jaws • Small, thought to be of paedomorphic origin • Little known, an extinct monophyletic lineage. 2 Class Anapsid Class Cephalaspidomorphi, osteostraci • Extinct, Silurian period • Extinct, early Silurian • 6-15 external branchial openings • No jaws • Reduced or lost anal fin • 10 pairs external gill openings • Short paired fins • Dorsal eyes • Series of large dorsal scutes • Pectoral fins (homology to • Hypocercal tail gnathostome pectoral fins not • No jaws known) • No massive head shield • Dorsal scutes reduced or lost Gnathostomata Class Placodermi • Monophyletic (including tetrapods) – Jaws derived from modified gill arches • Extinct – Three semicircular canals in inner ear • Jaws, no teeth – Paired fins (usually) • Head and trunk shield – Gill openings through slits (in fishes) • Braincase without nasal capsules – Dermal exoskeleton absent (usually) • Jaw muscle not external to mandibular arch • Head and shoulder with dermal plates 3 Class Chodrichthyes – cartilagenous fishes • Dermal skeleton • Endoskeleton mostly cartilage • Jaws – Upper jaw – – Lower jaw – – teeth • No lung or swim bladder • Urea retention • Spiral valve • Pectoral fins with keratin based spine • Paired nares • Spiracle • Reproduction – Internal fertilization – – gestation period – No parental care – Large egg cases, no larval stage Class Chondrichthyes, subclass Elasmobranchii, Order Carcharhiniformes, Class Chondrichthyes, subclass Elasmobranchii, Order Lamniformes, ground sharks mackerel sharks • Seven families, 10 genera, 15 species • Eight families, 49 genera, 270+ species • 2 dorsal fins • 2 dorsal fins, no spines • Five gill slits • Five gill slits, last 1-3 over pectoral fin • No nictitating membrane • No gill rakers • No barbels • Nictitating membrane • Spriacle behind eye • May have barbels or labial furrows • Examples • Spriacle usually absent • Mouth extends beyond eye • Oviparaous, ovoviviparous or viviparous • Examples 4 Class Chondrichthyes, subclass Elasmobranchii, Order Rajiformes, skates Class Chondrichthyes, subclass Elasmobranchii, Order Myliobatiformes, stingrays • Three families, >25 genera, >275 species • 33 genera, 178 species • Snout pointed • 4-5 pairs of gill slits • Pectoral disc usually rhomboid • Caudal fin and single dorsal fin reduced or • Thorns along midline of back absent • Caudal fin moderately well developed, • Sting from modified dermal denticle without barb, may have two dorsal fins sheathed in venomous tissue • Some electrogenic organs in tails • Males with enlarged spines near eyes • Pectoral disc rounded, oval or triangular • Oviparous • No thorns along midline • Ovoviviparous Class Chondrichthyes, subclass Elasmobranchii, Order Myliobatiformes, Class Chondrichthyes, subclass Holocephali, Family Chimeridae stingrays • 3 families, 6 genera, 33 species • Taxononomy recently revised, skates and rays were previously • Global distribution, marine only grouped together • 1 external gill opening, 4 covered by soft • Freshwater or marine operculum • two dorsal fins, first with venomous spine • teeth • large pectoral fins with fleshy base • elongate tail • Oviparous, • Upper jaw fused to cranium 5 Class Acanthodi – “spiny sharks” • Extinct, Silurian, Devonian • Earliest jawed fishes in the fossil record • Evolution: Acanthodii • Probably active mid-water and Teleostomi Sarcopterygii Dipnoi surface feeders Coelocanthomorpha • Freshwater and Marine Euteleostomi Actinopterygii Sarcopterygii Actinopterygii Euteleostomi 6.
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