Phylogeny & Diversification of Mammals

Phylogeny

study of the history, diversification, and relationships among taxa

• based on fossil evidence & molecular genetics

• often a conflict (morphological vs. molecular)

• usually depicted as “trees”

Morphology

form & structure of an organism

Homologous Trait

trait shared bc of a shared COMMON ANCESTOR

• humorous bone

Convergent Evolution

independent development of similar features

Molecular Traits

• use DNA and RNA

• compare amino acid sequences

Phylogenetic Trees

first shared derived characteristic

Monophyletic

includes all descendants from a common ancestor

Paraphyletic

does not include descendants from a common ancestor

Polyphyletic

a group of individuals considered together that do not have a common ancestor

George Gaylord Simpson

classification should reflect phylogeny & shared adaptations

“trash can” families/orders

Order Insectivora » Soricomorpha » Eulipotyphla

Cetartiodactyla

cetaceans » whales closely related to hippos

Astragalus Bone

unique tarsus thought only to occur in artiodactyls

Amniota

shelled egg

Synapsids

“mammal-like” reptiles

• branched from reptile lineage in Paleozoic era

• cotylosaurs - stem reptiles

• hole in the head ; temporal fenestra

Paleozoic Era

• invertebrates

• flourish

Mesozoic Era

• ‘age of dinosaurs’

• first ‘true’ mammals

• 2nd major radiation of insects

• radiation of angiosperms (flowering plants)

• 3 periods

• ends with mass extinction

Cretaceous Period

• separation of marsupial & placental lineages

• angiosperm radiation & 2nd insect radiation

• 140

Jurassic Period

• 200

• archaic mammals appear

Triassic Period

• ~250

• first true mammals appear

Cenozoic

“age of mammals”

• a lot more species become extinct

• headed towards another mass extinction

Last slide know*

carboniferous » paleogene

basically up to KPg kinda