EEB267H1 Study Guide - Final Guide: Aromatase, Ape, Prototheria
20 Jul 2013
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Synapomorphies of amniota: amniotic egg (amnion, chorion and allantois) Extraembryonic membranes are laid down by the developing embryo. Yolk sac is laid down by the mother (older than the amniota) becomes connected to the embryo. Position is unclear, because there are many extant living lineages separating the living groups of amniotes and because they have such unique characteristics. Synapomorphies: no teeth (keratinous beak, shell (carapace and plastron) usually covered with skin or scutes, vertebrae and ribs are fused to the carapace (except for the neck and tail, scapula is within the ribcage (shoulder blade) Problems with breathing arise because the ribs are attached to the outside of the thoracic cavity and the lungs are attached to the inside of the thoracic cavity. Normal breathing all based on the fact that ribs can move. Testuidine breathing: immovable ribs: dorsal side of the thoracic cavity is fused to the ribs, ventral side of the thoracic cavity is attached to the visceral cavity.
