Early Mammal Evolution

Cenozoic era

Age of mammals, they undergo big radiation and become dominant land animal. includes tertiary period where modern genera appear, and quaternary period (pleistocene and holocene) when modern species appeared.

Synapsids

Mammal like reptiles from the Paleozoic Era. Had 1 temporal opening where the postorbital and squamosal articulated above the hole. The earliest pre mammal branch from other reptiles.

Anapsids

No temporal openings (primitive condition), led to turtles.

Euryapsids

One temporal opening and post orbital and squamosal articulate below the hole. Extinct marine reptiles.

Mesozoic Era

Separated from the Paleozoic era by the late permian mass extinction. Contained the Triassic(therapsids and 1st true mammals), Jurrasic (archaic mammals appear), and cretaceous (1st marsupials and placentals)

Cynodonta

The most successful group of theridonts that developed into modern mammals by getting smaller, increasing the size of the temporal opening, formation of the zygomatic arch from temporal bar, evolving a single dentary bone as well as more complex dentition, secondary palate, 2 occipital condyles, legs under body, loss of lumbar ribs.

Diapsids

Two temporal openings. Led to lizards, snakes, and birds.

Tribosphenic molars

A different type of heterodonty in early therians that allowed teeth to occlude and form grinding and shearing surfaces.

Theridonts

A diverse group of carnivorous therapsids

Therapsids

A group of synapsids that had erect or sprawled hindlimbs vs. just sprawled hind limbs.

Early prototherians

Had clear signs of simple heterodonty with multituburculate teeth, had tricont molars (3cusps in row).