A debate among Nussbaum, Wilkinson, Laurin, and Reisz ended with the conclusion that the ancestral member of this group of organisms lacked EER; a central issue in this debate was the classification of caecilians.  
A debate among Nussbaum, Wilkinson, Laurin, and Reisz ended with the conclusion that the ancestral member of this group of organisms lacked EER; a central issue in this debate was the classification of caecilians.  Early members of this group of organisms could be distinguished from their ancestors by the presence of eleventh and twelfth cranial nerves and the astralagus bone in the ankle, and the Joggins fossils indicate that this group of organisms diverged into the synapsids and sauropsids. Another synapomorphy of this clade contains several sacs, including the allantois, the chorion, and its namesake sac, and its development permitted vertebrates to expand further inland.  For 10 points, name this clade that encompasses most living terrestrial animals and which is named for a structure which, in humans, is a fluid-filled membrane surrounding the fetus.
A debate among Nussbaum, Wilkinson, Laurin, and Reisz ended with the conclusion that the ancestral member of this group of organisms lacked EER; a central issue in this debate was the classification of caecilians.  
amniotes [accept word forms like amniotic, amniota, etc.]