The Phanerozoic Eon Eras Periods comments Paleozoic 541-252 MYA Pangean supercontinent Cambrian Ordovician Silurian Devonian Carboniferous Permian ends with first great extinction Mesozoic 252-66.5 MYA (“Age of Reptiles”) Laurasia and Gondwana supercontinents separated by equatorial Tethys Sea Triassic Jurassic Cretaceous ends with second great extinction Cenozoic 66.5 MYA-present (“Age of Mammals”) modern continents Paleogene Neogene
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Eras Periods comments - New Mexico State Universitylithornis.nmsu.edu/~phoude/background.pdf · Eras Periods comments Paleozoic 541-252 MYA Pangean supercontinent Cambrian Ordovician
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The Phanerozoic Eon
Eras Periods comments
Paleozoic 541-252 MYA Pangean supercontinent
Cambrian
Ordovician
Silurian
Devonian
Carboniferous
Permian ends with first great extinction
Mesozoic 252-66.5 MYA (“Age of Reptiles”) Laurasia and Gondwana supercontinents
separated by equatorial Tethys Sea
Triassic
Jurassic
Cretaceous ends with second great extinction
Cenozoic 66.5 MYA-present (“Age of Mammals”) modern continents
Paleogene
Neogene
Era Periods comments
Mesozoic 252-66.5 MYA (“Age of Reptiles”) Laurasia and Gondwana supercontinents
separated by equatorial Tethys sea
hotter and arid
TriassicGymnosperms dominant
first mammal-like reptiles
first dinosaurs
Jurassicformation of Atlantic Ocean begins
development of continental seaways
first birds
CretaceousAngiosperms dominant
ends with second great extinction
Monophyly – the property of an inclusive group of organisms of shared common ancestry
a b c d e
a b c d e
a b c d e
Polyphyly – the property of being unrelated by descent
Paraphyly – the property of a group of organisms of shared common ancestry that does not include all of the evolutionary derivatives of that common ancestor
Monophyletic groups are the only onesintended to be classified taxonomically
a b c d e
a b c d eParaphyletic groups are undesirable in classification because those organisms most closely related (i.e., a and b) are not grouped together
-most likely to have been based on superficiallyconspicuous traits, therefore many examples discoveredwith the application of molecular data to large samples
“Apes” are a paraphyletic group
guenons gibbons orang gorilla chimps human
Evolution of Reptiles from Amphibians
inferred from fossil record
Anthracosaur Labyrinthodonts –tetrapod amphibians
Cotylosaurs (Anapsids ) – stem reptiles
Diapsids – Lepidosaurs (lizards, snakes)
and Archosaurs (“ruling reptiles” dinosaurs, crocodiles, birds)
Synapsids – mammal-like reptiles
Evolution of Archosaurs
or “ruling reptiles”
A) Tarbosaurus and B) Tyrannosaurus skulls1) left lateral, 2) dorsal