-
derived characters of chordates
- notochord
- pharyngeal slits/clefts
- dorsal, hollow nerve cord
- muscular, post-anal tail
-
cephalochordata
- lancelets
- most chordate features retained as adults
- cirri - filter water that enters the mouth
- underground as adults
- minimal nervous, circulatory systems
-
urochordata
- tunicates (sea squirts)
- larval stage retains chordate features; mainly a dispersal stage
- undergoes metamorphosis
- adult stage is sessile filter feeder with incurrent and excurrent siphons
- chordate features in adult stage are highly reduced or disappear altogether
-
derives features of craniates
- cephalization in the head
- sensory organs
- more adapted to predation
- neural crest cells
- closed circulatory system with blood and hemoglobin; 2 chambered heart
- kidneys and excretion
- higher metabolic rate
- extensive muscular system
-
myxini
- hagfishes
- craniate basal group
- cartilaginous skull
- axial rod of cartilage for support on dorsal side
- slime glands
-
derived characters of vertebrates
- craniates with a backbone
- vertebrae encase spinal cord
- elaborate skull
- fins
-
petromyzontida
- lampreys
- cartilage skeleton
- persistent notochord
- cartilaginous projections around nerve cord serve as rudimentary vertebrae
- parasites; tongue that digs into prey and sucks out fluid
-
conodonts
- transitional stage
- mineralization of some structures
- ossification of dental elements first
- still jawless
-
derived characters of gnathostomes
- vertebrates with jaws (may have been derived from bones that support pharyngeal clefts)
- lateral line system and enhanced sensory organs
- mineralized endoskeleton
- larger brain
- diverged into 3 groups: chondrichthyes, osteichthes, tetrapods
-
chondrichthyes
- sharks, rays, relatives
- cartilaginous skeleton
- some traces of bone in teeth, vertebrae, scales
- carnivorous
- spiral valve inside instestines
- acute senses; electrical fields and vibrations
- buoyancy with fatty livers
- must move constantly to aerate gills
- eggs can be shed, born live, or develop inside mother
-
osteichthes
- gnathostomes with ossified skeleton
- includes all bony fishes and tetrapods
- 2 biggest clades: actinopterygii & sarcopterygii
-
actinopterygii
- ray-finned fishes
- tuna, seahorse, clownfish, etc.
- fins supported by rays
- operculum (moves water across gills) and swim bladders
-
sarcopterygii
- lobe-finned fishes
- actinistia (coelacanth) and dipnoi (lungfish)
- bones in fins allots for management in shallow water
-
tetrapods
osteichthes with 4 limbs
-
Tiktaalik
- shows characters of both tetrapods and fish
- bone girdles
- neck
- ribs
- fin is similar to forearm bones
-
Acanthostega
- limbs with digits
- retained an amphibious lifestyle
-
Amphibia
- partial water/land lives
- metamorphosis
- respiratory system (either gills, lungs, or skin)
- closed circulatory system with chambered heart
- eggs and external fertilization
- 3 main groups are urodela, anura, apoda
-
urodela
- salamanders
- retained tails and legs
-
anura
- frogs
- lost tail
- retained powerful hind legs
-
-
derived characters of amniotes
- tetrapods with amniotic egg
- well-adapted to living on land
- impermeable skin (keratin)
- ribcage for ventilation of lungs
- limbs elevate body
-
amniotic egg
- develops outside of mother's body
- extraembryonic layers derived from zygote
- all surrounded by albumen
- amnion - protects embryo; closest in proximity to embryo
- allantois - takes wastes
- chorion - gas exchange (egg shell is typically impermeable)
- yolk sac - contains nutrients
-
Reptilia
- scales (keratin)
- lungs
- internal fertilzation
- closed circulatory system with 3-4 chambered heart
- shelled eggs (calcium, leathery)
- 2 main lineages are parareptiles and diapsids (lepidosaurs and archesaurs)
-
parareptiles
- earliest reptiles, extinct
- large, quadrupeda
- herbivores
-
diapsids
- includes all living and extinct reptiles except turtles
- two temporal fenestrae
- includes archesaurs and lepidosaurs
-
archesaurs
- distinguished by certain skull features
- teeth in sockets
- crocodilians: crocodiles and alligators
- dinosaurs
-
dinosaurs
- part of archesaur line
- endothermic dinosaurs evolved into birds
- erect posture
- higher metabolic rate
- ribcage support and expansion (because of erect posture)
-
lepidosaurs
tuataras and squamates (true lizards, snakes)
-
tuataras (distinguishing characters from lizards)
- found only around New Zealand
- dorsal spines
- ossified teeth; double row on upper jaw, single row on lower jaw
-
turtles
- contradicting evidence for classification
- asynapsid (no temporal fenestrae)
-
derived characters of birds
- wings and feathers
- light skeleton with spongy bone
- no teeth
- no urinary bladder, single ovary
- 4 chambered heart
- endothermic and high metabolic rate
- acute senses of sight, fine muscle control
-
"microraptor" and Archaeopteryx
contain both reptilian and bird features
-
derived characters of mammals
- from synapside lineage
- modified/reduced temporal fenestra
- mammary glands
- hair/fat as insulation
- larger brain and braincase
- endothermic
- variation in teeth due to different diets
- remodeled jaw
- 4 chambered heart
- 3 lineages: monotremes, marsupials, eutherians
-
monotremes
- lay eggs
- nurse through skin after born
-
marsupials
- short gestation period
- complete embryonic development nursing from nipple in pouch
-
eutherians
- complete gestation
- placented
- born through birth canal as mini-adult
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