phylum Chordata
• around AT LEAST since Cambrian
– 2 cm long, no appendages or eyes
• for 200 my restricted to ocean,
~360 mya evolved appendages,
moved to land
• ~60,000 (?) extant species
– 5500 spp. mammals (and 1/5th of those = bats)
• although numbers not impressive,
size is:
– land = 90,000 lbs, ocean = 220,000 lbs
phylum Chordata
debated… so
going to follow
your frosh
textbook…
• subphylum Urochordata - sea squirts, tunicates
• subphylum Cephalochordata - lancets, amphioxus
• subphylum Craniata
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class Myxini - hagfish
class Cephalaspidomorphi - lamprey
class Chodrichthyes - sharks, rays, mantas
class Osteichthyes - bony fish
class Amphibia - amphibians
class Reptilia - lizards, turtles, snakes
class Aves - birds
class Mammalia (Prototheria, Theria, Eutheria)
Gnathostomes
Vertebrates
• notochord
What makes a chordate?
– present in all embryos, not all adults
– flexible rod, between digestive tube and (maybe) nerve
cord - support, purpose = muscle attachment
• dorsal hollow nerve cord
– develops from ectoderm
– in some develops into central nervous sys.
• pharyngeal gill slits or pouches
– embryos develop pouches, which develop into slits in some
(humans becomes ear, thymus, etc.)
• post-anal tail
– chordate tail extends past anus
– all embryos have, lost in many adults (locomotion)
hemichordates
• closest chordate outgroup
– deuterostome, no wat vasc sys
• studies focus on development
– embryogenesis homologs
• <200 spp.
• Camb-Carbon fossils
– extinct graptolites (sawblades)
subphylum Urochordata
• tunicates (“tunic”), sea squirts
– ~3000 spp., all marine, filter feeders
– solitary or colonial
• have all 4 as larvae
– adults retain only gill slits
• larval stage = dispersal
– short (few minutes?)
• adult stage = sessile
subphylum Cephalochordata
• lancelets, amphioxus
– ‘both pointed’
• brain but no head
• have all 4 as larvae AND adults
• ~25 marine spp, fish like, reduced
nervous system
• locally common, food resource
– naturally Jamaica (Discovery Bay),
Asia commercial harvest
subphylum Craniata
• chordates with a head
– have all 4 as larvae and adults, 9 classes
– hagfish, lampreys & 7 classes of gnathostomes
e.g., BF1 and Otx cause
swelling of dorsal nerve
cord tip in lancelets
same genes regulate fore,
mid, and hind brain in
craniates
class Myxini
• hagfish, agnathans, slime eel
– ~30 spp., all marine
• cold oceans, both hemispheres
• skull of cartilage, no jaws or
vertebrae
• dead/dying fish, mostly annelids
• slow metabolism – months w/o
eating
• most ~1’ long, some 2-3’
• spontaneously change sex
class Cephalaspidomorphi
• lamprey, have vertebrae of cartilage
– some highly reduced
• blood suckers
– mouth best way to tell apart
• ~30 spp., marine and freshwater
– cold water only
amphioxus:
• notocord
• epidermis
• myomeres
• digestive
• reproductive?
lamprey external:
• eyes
• buccal funnel/mouth/teeth
• nostril
• gills
• fins
• cloaca
lamprey internal:
• heart and ostia
• brain
• pineal gland
• liver
• olfactory sac
• cranial cartilage
• eye
• notocord
• nervous tissue
• myomeres
• ovary
• intestine
• gills
• kidney? (up by liver)