Part 5 – Living on Land From fish to (terrestrial) tetrapod

“fishes”tetrapods The Transition

Challenges of terrestrial living

“Fishes” Tetrapods

The players …..

Aquatic tetrapods

† Shallow water, freshwater aquatic tetrapod (lobe-finned fish)

Aquatic tetrapods

Icthyostega Internal choanae

Aquatic / terrestrial tetrapods

† Primitive aquatic tetrapods

† Primitive terrestrial tetrapods (on the way to amphibians)

Terrestrial tetrapods

2 terrestrial tetrapod groups

Amniotes (reptile/bird, mammal) (Lepospondyli) 1.

† Primitive amniotes (pre- reptile/bird, mammal) (Lepospondyli – husk vertebrae ) 1.

Temnospondyli 2. Amphibians + (many) extinct things

Temnospondyli 2. † Proto-Amphibians (split vertebrae)

2 terrestrial tetrapod groups

Tetrapods † aquatic tetrapods † semi-terrestrial tetrapods † Lepospondyli Amniotes † Temnospondyli Amphibians Terrestrial tetrapods

lobe-fin fish †early tetrapods Lepospondyli Amnoita Temnospondyli Class Amphibia † various dead ends aquatic terrestrial fish tetrapod

Some time scale 6 billion years

Cenozoic Mesozoic Paleozoic 600 million years

Paleozoic Fish Events

Paleozoic Tetrapod events (early)

Paleozoic Tetrapod events (late)

Paleozoic Earth

Ordovician terrestrial habitats

Devonian terrestrial habitats

Carboniferous terrestrial habitats

Carboniferous millipede tracks

Meganeura Carboniferous dragonfly 75 cm wingspan

Permian – cooler and drier

Permian Volcanism

Devonian – First tetrapods Panderichthys Tiktaalik Acanthostega Ichthyostega

Carboniferous – tetrapods diversify and move onto land Pederpes Loxomma Amphibamus Tuditanus

Permian – it all almost ends

Living on land

Pre-adaptations Lungs Limbs

Internal choanae Pre-adaptations

Support and Movement

Fish primitive (terrestrial) tetrapod Terrestrial tetrapods Vertebral innovations

Vertebral Column fishes, pre-terrestrial tetrapods

Vertebral Column terrestrial tetrapods

Terrestrial tetrapods zygapophyses

Early Tetrapods Terrestrial Aquatic

Limb Girdles

Fishes opercular bones present pectoral girdle skull connected *

Panderichthys Lobe-finned Fish Tiktaalik Basal tetrapod = “fish-o-pod” Opercular bones lost

Vantastega Skull / girdle connection lost

Tetrapods have necks

“fish” tetrapod “fish” tetrapod

Pelvic girdle “Fishes” No connection to vertebral column

Lobefin fish Primitive tetrapod no connection connection Pelvic girdle

Eryops Pectoral Pelvic

Eryops

Pre-amphibians Temnospondyli

living amphibian pelvic girdle

Appendicular Skeleton lobe-fin fish aquatic tetrapod

Appendicular Skeleton early terrestrial tetrapod later terrestrial tetrapod

“fish” tetrapod “fish” tetrapod

How many digits?

Physiology and soft anatomy

Switching from gill breathing (with lungs) to lung breathing

“Fish” – gills with lungs Tetrapod – lungs with gills

Gill breathing – with lungs

Lung breathing

lobe-fin fish †early tetrapods Lepospondyli Amnoita Temnospondyli Lissamphibia = Class Amphibia (s.s.) † various dead ends aquatic terrestrial fish tetrapod