EARTH 307: Lecture 18 Amphibians

Class Amphibia

• tetrapods with double respiration, through lungs and skin (therefore attached to aquatic mode of life because skin must be kept wet)

• able to move inland, for long distances but require aquatic environments for reproduction

• repro is similar to that of fishes, lay huge number of unprotected eggs in aquatic conditions, in terrestrial environments, the eggs would be dry out

• lung respiration is not active because amphibians did not evolve a chest bone

• Uppermost Devonian - Holocene

• rhipidistian anestors

Subclass Ichthyostegalia

• Uppermost Devonian - lower carboniferous

• most primitive amphibians

• acanthostega, ichthyostega are some of the uppermost devonian representatives

• pederpes from lower carboniferous present limbs with 5 toes, reduction from six or seven seen in older acanthostega, ichthyostega

Subclass temnospondyli

• temnospondyls are dominant amphibians in pennsylvanian - permian

  • surivived the great dying

  • existed until the lower cretaceous

• evolved into large sizes, 2m or more

• larger ones were crocodile-like with large skulls covered with plates

• from Ichthyostegalia ancestors

What were some characteristics of the late paleozoic temnospondyli?

• smaller ones started to evolve a body similar to modern amphibians

• ex. cacops of lower permian resembles frog (60cm)

Subclass Lissamphibia

• temnospondyli ancestors

• includes modern amphibians (frogs, newts, salamanders)

• rare is fs, especially in Mesozoic

• lower Triassic - holocene

Subclass anthracosauria

• amphibians from which reptiles evolved from

• predators, crocodile like with length of 4m

• Pennslyvanian - Permian, possible early triassic

• from Ichthyostegalia ancestors

• transition between two is gradual

• semi aquatic but could move inland over certain distances

• first discovered in scotland

1. Eusthenopteron

• marine

• upper devonian

• last FISH in the lineage towards amphibians

2. Tiktaalik

• 1.5 m in length

• boundary between fishes and amphibians

• limbs started to change long with body shape

• move in land

• semi-aquatic

• upper devonian

3. Acanthostega

• upper devonian

• semi-aquatic

• most primitive of land tetrapods

• well-developed limbs

• could move in land over short distances

• ribs identitical to those with fish ancestors

• body began to compress dorsally

• fed on small insects and worms

4. Pederpes

• lower mississippian

• oldest amphibian which is terrestrial

• number of toes reduced to 5 per limb in contrast to acanthostega which had 6-8