Post on 22-Aug-2020
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
Nanotyrannosaurus skull
Left posterior femur and left lateral pelvis
Saurischian (Antrodemus) Ornithischian (Thescelosaurus)
(Hogervorst, Bouma, and de Vos 2009 Acta orthopaedica 80:1-39)
Digitigrade
Deltopectoral crest
AntitrochanterPosture
metatarsals
tarsals
intertarsaljoint