|
|
|
|
|
|
|
|
|
|
|
|
The period
since the Cambrian
|
|
explosion is
known as the
|
|
|
Phanerozoic
and is divided
|
|
into three
eras: the Paleozoic,
|
|
the Cenozoic, and the
|
|
Mesozoic. These eras are
|
|
further
subdivided based on
|
|
|
discontinuities
in the fossil
|
|
|
record (i.e.
extinctions). In
|
|
|
class today,
we will examine
|
|
|
the most
recent mass
|
|
|
extinction
event, which marks
|
|
|
the boundary
between the
|
|
|
Mesozoic and
Cenozoic
|
|
|
periods.
|
|