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Evolution of the amniotes. Evolution of the amniotes. monophyletic the unifying synapomorphy… the terrestrial environment… truly terrestrial function of membranes? fertilization? development?. Evolution of the amniotes. Skeletal characteristics of early amniotes: palatoquadrate…
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Evolution of the amniotes • monophyletic • the unifying synapomorphy… • the terrestrial environment… • truly terrestrial • function of membranes? • fertilization? • development?
Evolution of the amniotes • Skeletal characteristics of early amniotes: • palatoquadrate… • anterior epipterygoid and posterior quadrate • articular bone… • articulates with quadrate • fenestra ovalis… • atlas/axis…
Ancestral anamniote condition gut wall posterior anterior YS embryonic coelom body wall
Initial stage of development developing amniotic folds
Derived amniote condition Derived Amniote Condition
Evolution of the amniotes Diadectomorphs Seymouriamorphs amniotes reptilomorph ancestor
Evolution of the amniotes synapsids diadectomorphs Seymouria amniotes reptilomorph ancestor
Evolution of the amniotes diapsids anapsids synapsids diadectomorphs Seymouria amniotes reptilomorph ancestor
Anapsids… The Turtles late Triassic… …fully formed 280 species morphologically homogeneous
carapace plastron bridges scutes reduced…
vertebral column and ribs… pectoral girdle and sternum… plastron hinged external and internal nostrils “beak”
ecologically diverse… habitat… trophic relations…
oviparous… burrows… eggs… temperature… predation…
Loggerhead sea turtles Caretta caretta