Part 1 Where does it start? Early Chordates, Craniate and vertebrate origins

Phylum Chordata

Animal Kingdom Vertebrates over here

Phylum Chordata Notochord, dorsal hollow nerve cord, pharyngeal slits, Chordata (animals with notochord at some stage in life cycle) Craniata (euchordates with a cranium) = Vertebrata Gnathostomata (Craniata with jaws) Teleostomi (bony fishes + tetrapods) Tetrapoda (four-limbed vertebrates) Amniota (tetrapods with embryos having extraembryonic membranes) Reptilia Protochordata Agnatha Osteichthyes (bony fishes) Urochordata (tunicates) Petromyzontida (lampreys) Actinopterygii (ray-finned fishes) Sarcopterygii (lungfishes, coelacanths) Amphibia Mammalia (mammals) Lepidosauria (lizards, snakes) Testudines (turtles) Crocodilia Aves (birds) Cephalochordata (lancelets) Myxini (hagfishes) Chondrichthyes (sharks, rays, chimaeras) Slime glands, accessory hearts Suckerlike oral disc, long larval stage, 7 pairs of gills Heterocercal caudal fin, placoid scales, cartilaginous skeleton Hair, mammary glands Notochord, dorsal hollow nerve cord, pharyngeal slits, postanal tail, endostyle Neural crest Distinct head and tripartite brain, paired specialized sense organs, 1 pair semicircular canals, glomerular kidney, ectodermal placodes 2 pairs semicircular canals, vertebrae Jaws, 3 pairs semicircular canals, paired appendages, gill filaments lateral to gill support Lung or swimbladder derived from gut, bony endoskeleton Unique supportive elements in skeleton or girdles of appendages Paired limbs used for terrestrial locomotion Egg with extraembryonic membranes Skull with upper and lower temporal fenestra, Beta-keratin in epidermis Phylum Chordata

Pikaia – a very early (fossil) chordate

Phylum Chordata - Origins Phylum Echinodermata Phylum Chordata - Origins Phylum Hemichordata

Carpoids …..a link between non-chordates and chordates? Fossil echinoderms …..a link between non-chordates and chordates?

Deuterostomia Ambulacraria Chaetognatha Xenoturbellida Echinodermata Hemichordata Chordata Xenoturbella Enteropneusta Pterobranchia Hooded circlet of spines around mouth Loss of gill slits Pentaradiality Endoskeleton of stereom ossicles Buccal diverticulum Mesocoelomic ducts Postanal tail Notochord Endostyle or thyroid gland Coelom tripartite Axial complex Unique larval morphology Diffuse nervous system Unusual ciliary structure Mouth not derived from blastopore Enterocoely Gill slits in pharynx Radial determinate cleavage

5 traits define all chordates Chordata (animals with notochord at some stage in life cycle) Craniata (euchordates with a cranium) = Vertebrata Gnathostomata (Craniata with jaws) Teleostomi (bony fishes + tetrapods) Tetrapoda (four-limbed vertebrates) Amniota (tetrapods with embryos having extraembryonic membranes) Reptilia Protochordata Agnatha Osteichthyes (bony fishes) Urochordata (tunicates) Petromyzontida (lampreys) Actinopterygii (ray-finned fishes) Sarcopterygii (lungfishes, coelacanths) Amphibia Mammalia (mammals) Lepidosauria (lizards, snakes) Testudines (turtles) Crocodilia Aves (birds) Cephalochordata (lancelets) Myxini (hagfishes) Chondrichthyes (sharks, rays, chimaeras) Slime glands, accessory hearts Suckerlike oral disc, long larval stage, 7 pairs of gills Heterocercal caudal fin, placoid scales, cartilaginous skeleton Hair, mammary glands Notochord, dorsal hollow nerve cord, pharyngeal slits, postanal tail, endostyle Neural crest Distinct head and tripartite brain, paired specialized sense organs, 1 pair semicircular canals, glomerular kidney, ectodermal placodes 2 pairs semicircular canals, vertebrae Jaws, 3 pairs semicircular canals, paired appendages, gill filaments lateral to gill support Lung or swimbladder derived from gut, bony endoskeleton Unique supportive elements in skeleton or girdles of appendages Paired limbs used for terrestrial locomotion Egg with extraembryonic membranes Skull with upper and lower temporal fenestra, Beta-keratin in epidermis 5 traits define all chordates

5 traits define all chordates Protochordata Agnatha Urochordata (tunicates) Petromyzontida (lampreys) Cephalochordata (lancelets) Myxini (hagfishes) 5 traits define all chordates Suckerlike oral disc, long larval stage, 7 pairs of gills Slime glands, accessory hearts *notochord *dorsal hollow nerve cord *pharyngeal slits *postanal tail *endostyle Neural crest

Chordate Traits Endostyle 11 11

Adaptive significance Gill arches Vertebral Column Complex central Nervous system Fig. 23.1 12

Pikaia – a very early (fossil) chordate 13 13

Phylum Chordata Notochord, dorsal hollow nerve cord, pharyngeal slits, Chordata (animals with notochord at some stage in life cycle) Craniata (euchordates with a cranium) = Vertebrata Gnathostomata (Craniata with jaws) Teleostomi (bony fishes + tetrapods) Tetrapoda (four-limbed vertebrates) Amniota (tetrapods with embryos having extraembryonic membranes) Reptilia Protochordata Agnatha Osteichthyes (bony fishes) Urochordata (tunicates) Petromyzontida (lampreys) Actinopterygii (ray-finned fishes) Sarcopterygii (lungfishes, coelacanths) Amphibia Mammalia (mammals) Lepidosauria (lizards, snakes) Testudines (turtles) Crocodilia Aves (birds) Cephalochordata (lancelets) Myxini (hagfishes) Chondrichthyes (sharks, rays, chimaeras) Slime glands, accessory hearts Suckerlike oral disc, long larval stage, 7 pairs of gills Heterocercal caudal fin, placoid scales, cartilaginous skeleton Hair, mammary glands Notochord, dorsal hollow nerve cord, pharyngeal slits, postanal tail, endostyle Neural crest Distinct head and tripartite brain, paired specialized sense organs, 1 pair semicircular canals, glomerular kidney, ectodermal placodes 2 pairs semicircular canals, vertebrae Jaws, 3 pairs semicircular canals, paired appendages, gill filaments lateral to gill support Lung or swimbladder derived from gut, bony endoskeleton Unique supportive elements in skeleton or girdles of appendages Paired limbs used for terrestrial locomotion Egg with extraembryonic membranes Skull with upper and lower temporal fenestra, Beta-keratin in epidermis Phylum Chordata

Chordata (animals with notochord at some stage in life cycle) Craniata (euchordates with a cranium) = Vertebrata Gnathostomata (Craniata with jaws) Teleostomi (bony fishes + tetrapods) Tetrapoda (four-limbed vertebrates) Amniota (tetrapods with embryos having extraembryonic membranes) Reptilia Protochordata Agnatha Osteichthyes (bony fishes) Urochordata (tunicates) Petromyzontida (lampreys) Actinopterygii (ray-finned fishes) Sarcopterygii (lungfishes, coelacanths) Amphibia Mammalia (mammals) Lepidosauria (lizards, snakes) Testudines (turtles) Crocodilia Aves (birds) Cephalochordata (lancelets) Myxini (hagfishes) Chondrichthyes (sharks, rays, chimaeras) Slime glands, accessory hearts Suckerlike oral disc, long larval stage, 7 pairs of gills Heterocercal caudal fin, placoid scales, cartilaginous skeleton Hair, mammary glands Notochord, dorsal hollow nerve cord, pharyngeal slits, postanal tail, endostyle Neural crest Distinct head and tripartite brain, paired specialized sense organs, 1 pair semicircular canals, glomerular kidney, ectodermal placodes 2 pairs semicircular canals, vertebrae Jaws, 3 pairs semicircular canals, paired appendages, gill filaments lateral to gill support Lung or swimbladder derived from gut, bony endoskeleton Unique supportive elements in skeleton or girdles of appendages Paired limbs used for terrestrial locomotion Egg with extraembryonic membranes Skull with upper and lower temporal fenestra, Beta-keratin in epidermis “Protochordates”

Craniates Craniata (euchordates with a cranium) Chordata (animals with notochord at some stage in life cycle) Craniata (euchordates with a cranium) Gnathostomata (Craniata with jaws) Teleostomi (bony fishes + tetrapods) Tetrapoda (four-limbed vertebrates) Amniota (tetrapods with embryos having extraembryonic membranes) Reptilia Protochordata Agnatha Osteichthyes (bony fishes) Urochordata (tunicates) Petromyzontida (lampreys) Actinopterygii (ray-finned fishes) Sarcopterygii (lungfishes, coelacanths) Amphibia Mammalia (mammals) Lepidosauria (lizards, snakes) Testudines (turtles) Crocodilia Aves (birds) Cephalochordata (lancelets) Myxini (hagfishes) Chondrichthyes (sharks, rays, chimaeras) Slime glands, accessory hearts Suckerlike oral disc, long larval stage, 7 pairs of gills Heterocercal caudal fin, placoid scales, cartilaginous skeleton Hair, mammary glands Notochord, dorsal hollow nerve cord, pharyngeal slits, postanal tail, endostyle Neural crest Distinct head and tripartite brain, paired specialized sense organs, 1 pair semicircular canals, glomerular kidney, ectodermal placodes 2 pairs semicircular canals, vertebrae Jaws, 3 pairs semicircular canals, paired appendages, gill filaments lateral to gill support Lung or swimbladder derived from gut, bony endoskeleton Unique supportive elements in skeleton or girdles of appendages Paired limbs used for terrestrial locomotion Egg with extraembryonic membranes Skull with upper and lower temporal fenestra, Beta-keratin in epidermis Craniates

Vertebrates 2 pairs semicircular canals, vertebrae Chordata (animals with notochord at some stage in life cycle) Craniata (euchordates with a cranium) = Vertebrata Gnathostomata (Craniata with jaws) Teleostomi (bony fishes + tetrapods) Tetrapoda (four-limbed vertebrates) Amniota (tetrapods with embryos having extraembryonic membranes) Reptilia Protochordata Agnatha Osteichthyes (bony fishes) Urochordata (tunicates) Petromyzontida (lampreys) Actinopterygii (ray-finned fishes) Sarcopterygii (lungfishes, coelacanths) Amphibia Mammalia (mammals) Lepidosauria (lizards, snakes) Testudines (turtles) Crocodilia Aves (birds) Cephalochordata (lancelets) Myxini (hagfishes) Chondrichthyes (sharks, rays, chimaeras) Slime glands, accessory hearts Suckerlike oral disc, long larval stage, 7 pairs of gills Heterocercal caudal fin, placoid scales, cartilaginous skeleton Hair, mammary glands Notochord, dorsal hollow nerve cord, pharyngeal slits, postanal tail, endostyle Neural crest Distinct head and tripartite brain, paired specialized sense organs, 1 pair semicircular canals, glomerular kidney, ectodermal placodes 2 pairs semicircular canals, vertebrae Jaws, 3 pairs semicircular canals, paired appendages, gill filaments lateral to gill support Lung or swimbladder derived from gut, bony endoskeleton Unique supportive elements in skeleton or girdles of appendages Paired limbs used for terrestrial locomotion Egg with extraembryonic membranes Skull with upper and lower temporal fenestra, Beta-keratin in epidermis Vertebrates

“Fishes” Chordata (animals with notochord at some stage in life cycle) Craniata (euchordates with a cranium) = Vertebrata Gnathostomata (Craniata with jaws) Teleostomi (bony fishes + tetrapods) Tetrapoda (four-limbed vertebrates) Amniota (tetrapods with embryos having extraembryonic membranes) Reptilia Protochordata Agnatha Osteichthyes (bony fishes) Urochordata (tunicates) Petromyzontida (lampreys) Actinopterygii (ray-finned fishes) Sarcopterygii (lungfishes, coelacanths) Amphibia Mammalia (mammals) Lepidosauria (lizards, snakes) Testudines (turtles) Crocodilia Aves (birds) Cephalochordata (lancelets) Myxini (hagfishes) Chondrichthyes (sharks, rays, chimaeras) Slime glands, accessory hearts Suckerlike oral disc, long larval stage, 7 pairs of gills Heterocercal caudal fin, placoid scales, cartilaginous skeleton Hair, mammary glands Notochord, dorsal hollow nerve cord, pharyngeal slits, postanal tail, endostyle Neural crest Distinct head and tripartite brain, paired specialized sense organs, 1 pair semicircular canals, glomerular kidney, ectodermal placodes 2 pairs semicircular canals, vertebrae Jaws, 3 pairs semicircular canals, paired appendages, gill filaments lateral to gill support Lung or swimbladder derived from gut, bony endoskeleton Unique supportive elements in skeleton or girdles of appendages Paired limbs used for terrestrial locomotion Egg with extraembryonic membranes Skull with upper and lower temporal fenestra, Beta-keratin in epidermis “Fishes”

“Fishes”: 6 distinct lineages Chordata (animals with notochord at some stage in life cycle) Craniata (euchordates with a cranium) = Vertebrata Gnathostomata (Craniata with jaws) Teleostomi (bony fishes + tetrapods) Tetrapoda (four-limbed vertebrates) Amniota (tetrapods with embryos having extraembryonic membranes) Reptilia Protochordata Agnatha Osteichthyes (bony fishes) Urochordata (tunicates) Petromyzontida (lampreys) Actinopterygii (ray-finned fishes) Sarcopterygii (lungfishes, coelacanths) Amphibia Mammalia (mammals) Lepidosauria (lizards, snakes) Testudines (turtles) Crocodilia Aves (birds) Cephalochordata (lancelets) Myxini (hagfishes) Chondrichthyes (sharks, rays, chimaeras) Slime glands, accessory hearts Suckerlike oral disc, long larval stage, 7 pairs of gills Heterocercal caudal fin, placoid scales, cartilaginous skeleton Hair, mammary glands Notochord, dorsal hollow nerve cord, pharyngeal slits, postanal tail, endostyle Neural crest Distinct head and tripartite brain, paired specialized sense organs, 1 pair semicircular canals, glomerular kidney, ectodermal placodes 2 pairs semicircular canals, vertebrae Jaws, 3 pairs semicircular canals, paired appendages, gill filaments lateral to gill support Lung or swimbladder derived from gut, bony endoskeleton Unique supportive elements in skeleton or girdles of appendages Paired limbs used for terrestrial locomotion Egg with extraembryonic membranes Skull with upper and lower temporal fenestra, Beta-keratin in epidermis “Fishes”: 6 distinct lineages

Tetrapods Paired limbs used for terrestrial locomotion Chordata (animals with notochord at some stage in life cycle) Craniata (euchordates with a cranium) = Vertebrata Gnathostomata (Craniata with jaws) Tetrapods Teleostomi (bony fishes + tetrapods) Tetrapoda (four-limbed vertebrates) Amniota (tetrapods with embryos having extraembryonic membranes) Protochordata Agnatha Osteichthyes (bony fishes) Reptilia Actinopterygii (ray-finned fishes) Urochordata (tunicates) Petromyzontida (lampreys) Mammalia (mammals) Lepidosauria (lizards, snakes) Testudines (turtles) Aves (birds) Sarcopterygii (lungfishes, coelacanths) Amphibia Crocodilia Cephalochordata (lancelets) Myxini (hagfishes) Chondrichthyes (sharks, rays, chimaeras) Hair, mammary glands Skull with upper and lower temporal fenestra, Beta-keratin in epidermis Suckerlike oral disc, long larval stage, 7 pairs of gills Egg with extraembryonic membranes Heterocercal caudal fin, placoid scales, cartilaginous skeleton Paired limbs used for terrestrial locomotion Slime glands, accessory hearts Unique supportive elements in skeleton or girdles of appendages Lung or swimbladder derived from gut, bony endoskeleton Jaws, 3 pairs semicircular canals, paired appendages, gill filaments lateral to gill support 2 pairs semicircular canals, vertebrae Distinct head and tripartite brain, paired specialized sense organs, 1 pair semicircular canals, glomerular kidney, ectodermal placodes Neural crest Notochord, dorsal hollow nerve cord, pharyngeal slits, postanal tail, endostyle

Chordata (animals with notochord at some stage in life cycle) Craniata (euchordates with a cranium) = Vertebrata Gnathostomata (Craniata with jaws) Teleostomi (bony fishes + tetrapods) Tetrapoda (four-limbed vertebrates) Amniota (tetrapods with embryos having extraembryonic membranes) Reptilia Protochordata Agnatha Osteichthyes (bony fishes) Urochordata (tunicates) Petromyzontida (lampreys) Actinopterygii (ray-finned fishes) Sarcopterygii (lungfishes, coelacanths) Amphibia Mammalia (mammals) Lepidosauria (lizards, snakes) Testudines (turtles) Crocodilia Aves (birds) Cephalochordata (lancelets) Myxini (hagfishes) Chondrichthyes (sharks, rays, chimaeras) Slime glands, accessory hearts Suckerlike oral disc, long larval stage, 7 pairs of gills Heterocercal caudal fin, placoid scales, cartilaginous skeleton Hair, mammary glands Notochord, dorsal hollow nerve cord, pharyngeal slits, postanal tail, endostyle Neural crest Distinct head and tripartite brain, paired specialized sense organs, 1 pair semicircular canals, glomerular kidney, ectodermal placodes 2 pairs semicircular canals, vertebrae Jaws, 3 pairs semicircular canals, paired appendages, gill filaments lateral to gill support Lung or swimbladder derived from gut, bony endoskeleton Unique supportive elements in skeleton or girdles of appendages Paired limbs used for terrestrial locomotion Egg with extraembryonic membranes Skull with upper and lower temporal fenestra, Beta-keratin in epidermis Amphibians

Amniota (tetrapods with embryos having extraembryonic membranes) Chordata (animals with notochord at some stage in life cycle) Craniata (euchordates with a cranium) = Vertebrata Gnathostomata (Craniata with jaws) Teleostomi (bony fishes + tetrapods) Tetrapoda (four-limbed vertebrates) Amniota (tetrapods with embryos having extraembryonic membranes) Protochordata Agnatha Osteichthyes (bony fishes) Amniotes Reptilia Actinopterygii (ray-finned fishes) Urochordata (tunicates) Petromyzontida (lampreys) Mammalia (mammals) Lepidosauria (lizards, snakes) Testudines (turtles) Aves (birds) Sarcopterygii (lungfishes, coelacanths) Amphibia Crocodilia Cephalochordata (lancelets) Myxini (hagfishes) Chondrichthyes (sharks, rays, chimaeras) Hair, mammary glands Skull with upper and lower temporal fenestra, Beta-keratin in epidermis Suckerlike oral disc, long larval stage, 7 pairs of gills Egg with extraembryonic membranes Heterocercal caudal fin, placoid scales, cartilaginous skeleton Paired limbs used for terrestrial locomotion Slime glands, accessory hearts Unique supportive elements in skeleton or girdles of appendages Lung or swimbladder derived from gut, bony endoskeleton Jaws, 3 pairs semicircular canals, paired appendages, gill filaments lateral to gill support 2 pairs semicircular canals, vertebrae Distinct head and tripartite brain, paired specialized sense organs, 1 pair semicircular canals, glomerular kidney, ectodermal placodes Neural crest Notochord, dorsal hollow nerve cord, pharyngeal slits, postanal tail, endostyle

Chordata (animals with notochord at some stage in life cycle) Craniata (euchordates with a cranium) = Vertebrata Gnathostomata (Craniata with jaws) Teleostomi (bony fishes + tetrapods) Tetrapoda (four-limbed vertebrates) Amniota (tetrapods with embryos having extraembryonic membranes) Reptilia Protochordata Agnatha Osteichthyes (bony fishes) Urochordata (tunicates) Petromyzontida (lampreys) Actinopterygii (ray-finned fishes) Sarcopterygii (lungfishes, coelacanths) Amphibia Mammalia (mammals) Lepidosauria (lizards, snakes) Testudines (turtles) Crocodilia Aves (birds) Cephalochordata (lancelets) Myxini (hagfishes) Chondrichthyes (sharks, rays, chimaeras) Slime glands, accessory hearts Suckerlike oral disc, long larval stage, 7 pairs of gills Heterocercal caudal fin, placoid scales, cartilaginous skeleton Hair, mammary glands Notochord, dorsal hollow nerve cord, pharyngeal slits, postanal tail, endostyle Neural crest Distinct head and tripartite brain, paired specialized sense organs, 1 pair semicircular canals, glomerular kidney, ectodermal placodes 2 pairs semicircular canals, vertebrae Jaws, 3 pairs semicircular canals, paired appendages, gill filaments lateral to gill support Lung or swimbladder derived from gut, bony endoskeleton Unique supportive elements in skeleton or girdles of appendages Paired limbs used for terrestrial locomotion Egg with extraembryonic membranes Skull with upper and lower temporal fenestra, Beta-keratin in epidermis Mammals (Synapsida)

Diapsida (“reptiles” + birds) Chordata (animals with notochord at some stage in life cycle) Craniata (euchordates with a cranium) = Vertebrata Gnathostomata (Craniata with jaws) Teleostomi (bony fishes + tetrapods) Tetrapoda (four-limbed vertebrates) Amniota (tetrapods with embryos having extraembryonic membranes) Reptilia Protochordata Agnatha Osteichthyes (bony fishes) Urochordata (tunicates) Petromyzontida (lampreys) Actinopterygii (ray-finned fishes) Sarcopterygii (lungfishes, coelacanths) Amphibia Mammalia (mammals) Lepidosauria (lizards, snakes) Testudines (turtles) Crocodilia Aves (birds) Cephalochordata (lancelets) Myxini (hagfishes) Chondrichthyes (sharks, rays, chimaeras) Slime glands, accessory hearts Suckerlike oral disc, long larval stage, 7 pairs of gills Heterocercal caudal fin, placoid scales, cartilaginous skeleton Hair, mammary glands Notochord, dorsal hollow nerve cord, pharyngeal slits, postanal tail, endostyle Neural crest Distinct head and tripartite brain, paired specialized sense organs, 1 pair semicircular canals, glomerular kidney, ectodermal placodes 2 pairs semicircular canals, vertebrae Jaws, 3 pairs semicircular canals, paired appendages, gill filaments lateral to gill support Lung or swimbladder derived from gut, bony endoskeleton Unique supportive elements in skeleton or girdles of appendages Paired limbs used for terrestrial locomotion Egg with extraembryonic membranes Skull with upper and lower temporal fenestra, Beta-keratin n epidermis Diapsida (“reptiles” + birds)

Chordata (animals with notochord at some stage in life cycle) Craniata (euchordates with a cranium) = Vertebrata Gnathostomata (Craniata with jaws) Teleostomi (bony fishes + tetrapods) Tetrapoda (four-limbed vertebrates) Amniota (tetrapods with embryos having extraembryonic membranes) Reptilia Protochordata Agnatha Osteichthyes (bony fishes) Urochordata (tunicates) Petromyzontida (lampreys) Actinopterygii (ray-finned fishes) Sarcopterygii (lungfishes, coelacanths) Amphibia Mammalia (mammals) Lepidosauria (lizards, snakes) Testudines (turtles) Crocodilia Aves (birds) Cephalochordata (lancelets) Myxini (hagfishes) Chondrichthyes (sharks, rays, chimaeras) Slime glands, accessory hearts Suckerlike oral disc, long larval stage, 7 pairs of gills Heterocercal caudal fin, placoid scales, cartilaginous skeleton Hair, mammary glands Notochord, dorsal hollow nerve cord, pharyngeal slits, postanal tail, endostyle Neural crest Distinct head and tripartite brain, paired specialized sense organs, 1 pair semicircular canals, glomerular kidney, ectodermal placodes 2 pairs semicircular canals, vertebrae Jaws, 3 pairs semicircular canals, paired appendages, gill filaments lateral to gill support Lung or swimbladder derived from gut, bony endoskeleton Unique supportive elements in skeleton or girdles of appendages Paired limbs used for terrestrial locomotion Egg with extraembryonic membranes Skull with upper and lower temporal fenestra, Beta-keratin in epidermis

Notochord, dorsal hollow nerve cord, pharyngeal slits, Chordata (animals with notochord at some stage in life cycle) Craniata (euchordates with a cranium) = Vertebrata Gnathostomata (Craniata with jaws) Teleostomi (bony fishes + tetrapods) Tetrapoda (four-limbed vertebrates) Amniota (tetrapods with embryos having extraembryonic membranes) Reptilia Protochordata Agnatha Osteichthyes (bony fishes) Urochordata (tunicates) Petromyzontida (lampreys) Actinopterygii (ray-finned fishes) Sarcopterygii (lungfishes, coelacanths) Amphibia Mammalia (mammals) Lepidosauria (lizards, snakes) Testudines (turtles) Crocodilia Aves (birds) Cephalochordata (lancelets) Myxini (hagfishes) Chondrichthyes (sharks, rays, chimaeras) Slime glands, accessory hearts Suckerlike oral disc, long larval stage, 7 pairs of gills Heterocercal caudal fin, placoid scales, cartilaginous skeleton Hair, mammary glands Notochord, dorsal hollow nerve cord, pharyngeal slits, postanal tail, endostyle Neural crest Distinct head and tripartite brain, paired specialized sense organs, 1 pair semicircular canals, glomerular kidney, ectodermal placodes 2 pairs semicircular canals, vertebrae Jaws, 3 pairs semicircular canals, paired appendages, gill filaments lateral to gill support Lung or swimbladder derived from gut, bony endoskeleton Unique supportive elements in skeleton or girdles of appendages Paired limbs used for terrestrial locomotion Egg with extraembryonic membranes Skull with upper and lower temporal fenestra, Beta-keratin in epidermis

“Protochordates” Not craniates – but the same phylum

Subphylum Cephalochordata lancetes, amphioxus

notochord nerve cord perforated pharynx endostyle post-anal tail

Subphylum Craniata 31

Subphylum Craniata

Chordata (animals with notochord at some stage in life cycle) Craniata (euchordates with a cranium) = Vertebrata Vertebrata Gnathostomata (Craniata with jaws) Teleostomi (bony fishes + tetrapods) Protochordata Agnatha Osteichthyes (bony fishes) Craniata Actinopterygii (ray-finned fishes) Urochordata (tunicates) Petromyzontida (lampreys) Mammalia (mammals) Sarcopterygii (lungfishes, coelacanths) Amphibia Cephalochordata (lancelets) Myxini (hagfishes) Chondrichthyes (sharks, rays, chimaeras) Hair, mammary glands Suckerlike oral disc, long larval stage, 7 pairs of gills Heterocercal caudal fin, placoid scales, cartilaginous skeleton Paired limbs used for terrestrial locomotion Slime glands, accessory hearts Unique supportive elements in skeleton or girdles of appendages Lung or swimbladder derived from gut, bony endoskeleton Jaws, 3 pairs semicircular canals, paired appendages, gill filaments lateral to gill support 2 pairs semicircular canals, vertebrae Distinct head and tripartite brain, paired specialized sense organs, 1 pair semicircular canals, glomerular kidney, ectodermal placodes Neural crest Notochord, dorsal hollow nerve cord, pharyngeal slits, postanal tail, endostyle

Vertebrata Craniata

Craniate innovations Cranium 35

Craniate innovations Tripartite brain Forebrain Midbrain Hindbrain

Complex Cranial Sense organs Craniate innovations Complex Cranial Sense organs Olfaction Vision Hearing (otic)

Inner ear with at least one semicircular canal Craniate innovations Inner ear with at least one semicircular canal

neural crest cells ectodermal placodes Unique embryonic tissues Craniate innovations ? Unique embryonic tissues neural crest cells ectodermal placodes 39

Acraniate Chordate Craniate

Very early craniates (probably) †Myllokunmingia † Haikouichthys †others

Very early craniates (probably) †Myllokunmingia † Haikouichthys †others

Relationships under debate †Myllokunmingia † Haikouichthys

Most primitive (living) craniate Hagfishes

Vertebrata Craniata

Vertebrata Vertebrates

Vertebrate innovations Vertebrae

Vertebrate innovations Inner ear with at least two semicircular canals

All sorts of new physiology Vertebrate innovations All sorts of new physiology

Most primitive living vertebrate Lampreys

Vertebrata Vertebrates Craniates

Craniates Vertebrates