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Important groups among tetrapods
- baphetidae=eucritta and megalocephalus
Dotted lines hypothesizing where groups split on a cladogram for which there is no fossil evidence.
- -lower carboniferous of w. Virginia
- -long bodied, 40 vertebrae, broad tail, short limbs
- -lateral lines indicate aquatic lifestyle
- Eucritta that fed on arthropods and lived in the midland valley of Scotland.
- megalocephalus, early Carboniferous, lateral line canals, adductor muscles are reconstructed to close the jaws, marginal and palatial teeth, first evidence of depressor mandibulae muscle
Why did vertebrates move to land?
They were probably trying to stay in the water! Lungfishes and other "walking catfishes" today, can survive out of water long enough to leave a drying pond in search of a better water source.
We're a group in the Linnaean classification scheme but were polyphyletic. No longer describes a single related group but reflects the complex enamel of teeth of several amphibian lineages.
Eusthenopteron and pandericthyes (Devonian)
- balenerpeton (Carboniferous)
- proximal limbs similar to other tetrapods but more fingers and toes.
- more obviously a swimmer with weak front arms
- 8 toes
- more robust possibly could have lifted itself
- six toes, ? Fingers
- Animals with more than five fingers or toes.
- five is not set in stone.
Allow for repetition of body parts or elements.
- Period when the continents were joining and most areas of amphibian evolution were tropical
- coal forests developing at this time
- large fauna identified from scotland including Balenerpeton and Eucritta
- Lower Carboniferous (Scotland)
- otic notch probably really a spiracle (gill opening to get more oxygen for the brain like in sharks)
- itsy bitty forelimbs
- Main amphibian group
- abundant in Triassic lived into cretaceous
- broad skulls adapted for sucking in prey underwater
- breathed using buccal pumping by broad mouths and short straight ribs
- example of extant amphibian suction feeding
- 40 families, 170 genera
- Upper Carboniferous of nova scotia
- broad mid palatial open space (= interptertyoid vacuity)
- narrow process anterior from braincase running across vacuity
- paired, broad flat anterior vomers
- stout arms and legs-strong hip/shoulder girdles
- slender stapes
- terrestrial habits
- Succeeded rhinesuchids world wide
- triassic only
- flattened skulls
- small limbs
- reduced ossification
- Skulls may be a meter long
- largest among the temnospondyls
- 0.5-1 meter long
- broad skulls with lateral line groves
- Erupts and edops
- 1-2 meters long
- a top preditor
- Ex. Cacops, most terrestrial amphibians
- probably fully terrestrial
Pineal/parietal "eye" opening
lower triassic, long thin snouts-marine
- lower permain, long snouted.
- possibly gave rise to trematosaurus-gharial-like fish eaters
- Upper carboniferous
- first with small enough stapes for impedance matching ear which amplifies force of sounds transmitted through air to match to fluid-filled inner ear - force magnified proportional to area of tympanum and stapes footplate
- Upper Permian-lower Triassic
- south africa
- medium to large
- evolved from eryopoids
Small, poorly ossified external gills
Describes vertebral anatomy but is not A Unified group
- no supratemporal bone
- no stapedial foramen
- cylindrical vertebrae of pleurocentra only
- neural arches and centra fuse indistinguishably early in ontogeny
- no atlantal intercentrum
- largest group of lepospondyls
- both aquatic and terrestrial; mainly terrestrial
- carboniferous and Permian
- ex: panthylus and pelodosotus
- Entirely aquatic
- newt like with long laterally compressed tails
- relatively small, paired limbs
- early species have cranial kinesis (lost in diplocaulis)
- funky shaped head may have been used to support a longer lateral line system.
- appear cloaest to labyrinthodonts
- Lower permian
- no cranial kinesics and dorsoventrally flattened skulls
- palatal fused to braincase
- palatal vacuities
- dorsoventral undulation
- N. Africa, N. America and Europe
- Most snakelike and specialized
- Up to 230 vertebrae- lack limbs and limb girdles
- Mid Jurassic-Miocene of europe
- salamander like and confused with them
- triangular fused trontals
- cervical vertebrae reduced to two fused
- (some of the first animals that had differentiated teeth, some of the earliest known herbivores)
- jointed skull that allowed flexion during jaw opening
- short neck, large vertebrae, flat sided tail-aquatic
- ex: empedias
- Early permian
- 600 mm long
- active terrestrial animal
- midwestern united states and Germany
- ex: Kotlassia-russian, broad skulls; piscivorous, terrestrial and aquatic forms both, Permian
- Heavy, massive limb girdles, short limbs, heavy vertebrae and ribs
- late Carboniferous and early Permina
- Herbivore-short, blunt teeth for chopping
- Modern amphibians-4000 species-4 clades
- albanerpetontids-extinct-basal outgroup for amphibia
- anurans-salientia (frogs and toads)
- urodeles (newts and salamanders)
- Gymniophonians (limbless caecilians)
- All have bicuspid pedicellate teeth
- arose from temnospondyls
- frogs and salamders=sister group (Batrachia)
- Most components of vertebrae evolved separately and fused in different patterns among different vertebrate groups.
- vertebral structure varies in accordance with need to resist forces.
- differential directional forces depend on movements and postures of individual species.
Evolution of differences in pectoral girdles
- Pectoral girdles evolved to simpler forms, loss of bones and fusions.
- reorientation for different limb functions
- pelvic girdles mirror this
- Basic organization of manus and pes
- early ability to identify bones of limbs
- homologous to those of later tetrapods
Locomotion changes on land
- Locomotion in early transition onto land used lateral undulation
- limbs strengthen to push animal forward
- Balance must be maintained once body is lifted from ground
- Limb reorientation for quadrupedal walking in early tetrapods
- Rotation of limbs, especially distal elements, for increased efficiency with limb reoriented to be placed under main axis of body
How does locomotion change
- from later undulation alone to later undulation with movement of individual limbs in a specific sequence
- tripod of support must be maintained within center of gravity for balance
difficulties in ID of species
- In many cases, interpretation and identification of elements has been difficult.
- Often animals are initially described as one species, and later changed to be included in different groups.
- Different growth stages may affect species identification.
- Lower Carboniferous of W. Virginia
- long bodied, 40 vertebrae, broad tail, short limbs
- lateral lines indicates aquatic lifestyle
Mammals are pleural centrum dominant
Legs under body vs sprawled locomotion with limbs to the outside