Evolution of the amniotes Evolution of the amniotes

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… anterior epipterygoid and posterior quadrate articular bone… articulates with quadrate fenestra ovalis… atlas/axis…

Ancestral anamniote condition gut wall posterior anterior YS body wall embryonic coelom

Initial stage of development developing amniotic folds

Later stage of development ch

Derived amniote condition Derived Amniote Condition

Evolution of the amniotes Diadectomorphs Seymouriamorphs amniotes reptilomorph ancestor

Seymouria…

Diadectomorphs

Evolution of the amniotes synapsids diadectomorphs Seymouria amniotes reptilomorph ancestor

Evolution of the amniotes anapsids diapsids synapsids diadectomorphs Seymouria amniotes reptilomorph ancestor

Diapsids

Diapsids

Diapsids

Diapsids

Diapsids

Diapsids

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…

3 snapper stories…

Loggerhead sea turtles Caretta caretta

green sea turtles

waves…