Osteichthyes Osteichth ancestor Acanthodians Actinistia - Coelacanth Actinopterygii Sarcopterygii Osteichth ancestor

Latimeria chalumnae

need africa-indian ocean map here

Osteichthyes Actinistia - Coelacanth Dipnoi - lungfishes Sarcopterygian ancestor

Dipnoi

Osteichthyes Actinistia - Coelacanth Dipnoi - lungfishes Osteolepiformes Sarcopterygian ancestor

I am often nervous when I fly…

Evolution of tetrapods Ichthyostega Eusthenopteron “50 things…” Osteolepiform ancestor

Evolution of tetrapods Eusthenopteron bones of dermal skull roof bones of appendicular skel labyrinthodont teeth palatine fangs Osteolepiform ancestor

Ichthyostega

Evolution of tetrapods Ichthyostega Eusthenopteron Osteolepiform ancestor

appendicular skeleton… labyrinthodont teeth palatine fangs terete Eusthenopteron: dermal skull roof… appendicular skeleton… labyrinthodont teeth palatine fangs terete large, predatory, freshwater well-developed median fins occipital condyles, notochord vertebral centra (PC and IC) ribs… bones of dermal skull roof similar in shape and pattern to early tetrapods no occipital condyles notochord remains and extends into braincase vertebral centra: a dorsal and posterior pleurocentrum and a ventral and anterior intercentrum laterally or dorsally directed ribs associated with pleurocentrum bones of appendicular skeleton similar in arrangement to early tetrapods (“labyrinthodont amphibians”)

Evolution of tetrapods a fish!!!! Panderichthyes Eusthenopteron dorsoventrally flattened dorsal orbits reduced median fins frontal bones (!) Osteolepiform ancestor

Evolution of tetrapods Tiktaalik Panderichthyes Eusthenopteron head… pectoral girdle… pectoral fin… dorsoventrally flattened head disassociation of pectoral girdle from head skeleton bones of pectoral fin articulate and have postures similar to those of early tetrapods shorter, thicker digits on pectoral appendage; fewer lepidotrichia Osteolepiform ancestor

Evolution of tetrapods Acanthostega Tiktaalik Panderichthyes zygapophyses iliac crest… ribs… Eusthenopteron Osteolepiform ancestor

Acanthostega

Ichthyostega

Evolution of tetrapods Ichthyostega Ichthyostega Acanthostega Tiktaalik olecranon process Panderichthyes Eusthenopteron Osteolepiform ancestor

Evolution of tetrapods Tulerpeton Ichthyostega Acanthostega Tiktaalik reduction of digit # Panderichthyes Eusthenopteron Osteolepiform ancestor

Evolution of tetrapods “crown tetrapods” Tulerpeton Ichthyostega Acanthostega Tiktaalik occipital condyles notochord… Panderichthyes Eusthenopteron notochord excluded from braincase Osteolepiform ancestor

50 things… Tournasian… the tournasian gap - 10 my or so Devonian was the age of fishes, but early evolution of tetrapods occurred during the later part of the Devonian by the Tournasian (early carboniferous) early tetrapods were well established few fossils from early carboniferous… Tournasian…

Lepospondyls: an unresolved polychotomy… Batrachomorphs intercentra cheekbones firmly attached toes 4/5 Reptilomorphs pleurocentra cheekbones loosely attached toes 5/6 crown tetrapods

Problems posed by the terrestrial environment

problems posed by the terrestrial environment H20 in terrestrial environment… O2 in the terrestrial environment… these affect… water balance (organisms are…) gas exchange – mechanism, rate internal transport mechanisms metabolic rate… % of o2 in air - 20.95; in water at sea level and 0oC - 14.16 mg/l or 14.16 ppm – presence of lots of oxygen allows higher metabolic rate

problems posed by the terrestrial environment specific heat capacity? water = 1.0 air = 0.24 thermoregulation difficult… necessary… thermoregulation difficult in the aquatic environment - high heat capacity of water thermoregulation is necessary in the terrestrial environment - great temperature fluctuation

problems posed by the terrestrial environment density… viscosity… better support different locomotion patterns buoyancy: (go swimming in the ocean…) viscosity: dictates/allows changes in locomotion

problems posed by the terrestrial environment Reproduction… fertilization (deposition/transport of gametes) development dispersal