Key Terms
Defining features
No jaws, no paired lateral fins, no bone in scales, no internal ossification
Cannot survive far from water
Eggs have no shell, dehydrate quickly in dry environments; reproduction tied to aquatic environments.
Key innovation
Amniotic egg with four extraembryonic membranes - freed reproduction from water dependence.
Anapsids
No temporal fenestrae (openings behind eye) Synapsids: one temporal fenestra - gave rise to mammals Diapsids: two tempor
Pterosaurs
NOT dinosaurs; wings formed by skin membrane attached to elongated fourth finger; hollow bones; flew/soared ~230-65 MYA
Enantiornithes
Dominant bird group during Cretaceous; retained teeth; went extinct at end of Cretaceous
Ornithurae
Clade with short fused tail (pygostyle); survived Cretaceous; gave rise to modern birds
Hair
Made of keratin; insulation; sensory (vibrissae/whiskers); social signaling; camouflage
Brain
Corpus callosum links two cerebral hemispheres (eutherians only); highly folded cerebral cortex in many species; divided
Circulatory
Four-chambered heart; enucleated red blood cells (unique to mammals; birds and other vertebrates have nucleated RBCs); s
Kidneys
Loop of Henle allows highly concentrated urine; no renal portal system (present in all other vertebrates except jawless
Synapsids
Single temporal fenestra; gave rise to mammals; only living synapsids are mammals Therapsids: advanced synapsids; cynodo
MYA
Oldest known primate-like fossils (proto-primates; squirrel-like) ~55 MYA: first true primates (Eocene; resembled modern
New World monkeys (Platyrrhini)
Broad noses; all arboreal; many have prehensile tails Old World monkeys (Catarrhini): narrow downward- pointing noses; a
Key hominin features distinguishing humans
Bipedalism, increased brain size, fully opposable thumb