Hemichordates and Invertebrate chordates 1 Protochordate taxa Phylum. Hemichordata Class. Enteropneusta Class. Pterobranchia Phylum. Chordata Subphylum. Urochordata Subphylum. Cephalochordata Subphylum. Vertebrata 2! Animal innovations (Symplesiomorphies) Pharyngeal gill slits Dorsal hollow nerve cord! Porifera Placozoa Cnidaria Ctenophora Platyhelminthes Gastrotricha Gnathostomulida Cycliophora Rotifera Annelida Mollusca Sipuncula Nemertea Bryozoa Brachiopoda Phoronida Arthropoda Onychophora Tardigrada Nematomorpha Nematoda Priapulida Kinorhyncha Loricifera Echinodermata Hemichordata Chordata Page 1
! Hemichordata (Autapomorphies) Stomochord proboscis complex Glomerulus! Porifera Placozoa Cnidaria Ctenophora Platyhelminthes Gastrotricha Gnathostomulida Cycliophora Rotifera Annelida Mollusca Sipuncula Nemertea Bryozoa Brachiopoda Phoronida Arthropoda Onychophora Tardigrada Nematomorpha Nematoda Priapulida Kinorhyncha Loricifera Echinodermata Hemichordata Chordata Hemichordate Proboscis (protocoel) Collar (mesocoel) Branchiogenital trunk (metacoel) Anus Gill slits Intestinal trunk (metacoel) Hepatic (metacoel) 5 Feeding Proboscis Rejected particles Gill pores Gut Collar Preoral ciliary organ Esophagus Food entering mouth 6 Page 2
Proboscis complex Mesocoel Heart vesicle Glomerulus Protocoel Mouth Stomocord 7 Acorn worm burrow 8 Locomotion 9 Page 3
Hemicordate Collar (mesocoel) Proboscis (protocoel) Trunk (metacoel) 10 Hemichordate Collar (mesocoel) Proboscis (protocoel) Branchiogenital trunk (metacoel) Anus Gill slits Intestinal trunk (metacoel) Hepatic trunk (metacoel) 11 Acorn worm burrow 12 Page 4
Pterobranchia 13 Pterobranchia Tentacles (mesocoel) Arms Anus Zooid Cephalic shield (protocoel) Mouth Collar Trunk (metacoel) Contractile Stalk (metacoel) 14 Pterobranchia Tentacles Arm Spine Cephalic shield Trunk Collar Stalk 15 Page 5
Chordates? 16! Chordata (Autapomorphies) Neurotube-notochord-mesoderm complex Pharyngeal slits and endostyle Post-anal tail and tadpole swimming Porifera Placozoa Cnidaria Ctenophora Platyhelminthes Gastrotricha Gnathostomulida Cycliophora Rotifera Annelida Mollusca Sipuncula Nemertea Bryozoa Brachiopoda Phoronida Arthropoda Onychophora Tardigrada Nematomorpha Nematoda Priapulida Kinorhyncha Loricifera Echinodermata Hemichordata! Chordata Chordate Phylogeny Cephalochordata Urochordata Vertebrata (Craniata)!! Chordata (autapomorphies) Neurotube-notochord-mesoderm complex Pharyngeal slits and endostyle Post-anal tail and tadpole swimming BIO2135 Animal Form & Function 18 Page 6
Pikaia: The chordate ancestor 19 Neurotube-notochord-mesoderm complex Neural crest Endoderm Ectoderm 20 Neurotube-notochord-mesoderm complex 21 Page 7
Fibrous sheath Elastic sheath 22 Dorsal hollow nerve chord 23 Origins of segmentation Ectoderm Nerve cord Somite (myomere) Archinephric duct Dorsal aorta Nephron Endoderm 24 Page 8
Pharyngeal gill slits and endostyle Endostyle 25 Segmentation and tadpole like swimming Post anal segments (Tail) 26 Chordate Phylogeny Cephalochordata Urochordata Vertebrata (Craniata)!! Cephalochordata (autapomorphies) Assymetric planktonic larval stage Extension of muscular notochord beyond neural tube Staggered myomeres and mouth a modified gill slit BIO2135 Animal Form & Function 27 Page 9
Cephalochordata 28 Cephalochordata Nerve cord Cecum Intestine Tail Mouth Endostyle Pharyngeal gill slits Atriopore Anus 29 Feeding Epibranchial groove Rostrum Vestibule Buccal cirri Wheel organ Mouth in velum Endostyle Gills 30 Page 10
Cross section (Cephalochordata) Neural tube Myomeres Atrium Gill Bars Pharynx region Endostyle Intestinal region 31 Chordate Phylogeny Cephalochordata Urochordata Vertebrata (Craniata)!! Symplesiomorphy Change in notochord from stack of coins to hollow elastic tube BIO2135 Animal Form & Function 32 Chordate Phylogeny Cephalochordata Urochordata Vertebrata (Craniata)!! Urochordata (autapomorphies) Tunicin cuticle Reversible heart beat Reduction of genome BIO2135 Animal Form & Function 33 Page 11
Urochordates Mouth Atrium Endostyle Pharyngeal gill slits Gonad Stomach 34 Urochordate larva Incurrent siphon Excurrent siphon and anus Dorsal tubular nerve cord Endostyle Pharyngeal gill slits Post anal segments (Tail) 35 Ascidian larva Pharyngeal basket Branchial siphon Ocellus Atrial siphon Endostyle Adhesive papillae Anus Tunic Heart Stomach Intestine 36 Page 12
Urochordate metamorphosis 37 Protochordate taxa Phylum. Hemichordata Class. Enteropneusta Class. Pterobranchia Phylum. Chordata Subphylum. Urochordata Subphylum. Cephalochordata Subphylum. Vertebrata 38 Cephalochordates 39 Page 13
Cephalochordata Nerve cord Cecum Intestine Tail Mouth Endostyle Pharyngeal gill slits Atriopore Anus 40 Feeding Epibranchial groove Rostrum Vestibule Buccal cirri Wheel organ Mouth in velum Endostyle Gills 41 Proboscis complex Mesocoel Heart vesicle Glomerulus Protocoel Mouth Stomocord 42 Page 14