Grimoire for the Apprentice Wizard

Course Two: Nature 55

Cycles of Geological Time

(Each loop of the spiral averages 37 million years.)

Geological Ages Duration How long ago

CENOZOIC (“recent life”) 0-65 mya

Neogene 23 my...0-23 mya... Mammals; humans.

Recent (Holocene) 0-10,500 ya Humans come to

dominate Earth.

Pleistocene 01.5-2 mya Ice Age; giant

mammals.

Pliocene 2-5 mya More mammals.

Miocene 5-23 mya Mammals,

earliest hominids.

Paleogene 42 my 65-23 mya Giant mammals.

Oligocene 23-34 mya Oligocene ends with

widespread extinctions.

Eocene 34-55 mya Mammals, giant birds.

Paleocene 55-65 mya With dinosaurs gone,

Age of Mammals begins.

MESOZOIC (“middle life”) 65-290 mya Cretaceous ends with

extinction of 85% of all life.

Cretaceous 65-141 mya Hadrosaurs, carnosaurs,

ceratopsians, raptors.

(Upper Cretac.) 34 my 65-99 mya Plesiosaurs, giant

pterosaurs, hadrosaurs.

(Lower Cretac.) 42 my 99-141 mya Ichthyosaurs, pterosaurs.

Jurassic 141-202 mya Greatest diversity

of dinosaurs.

(Upper Jurassic) 39 my 141-180 mya Big dinosaurs: stegosaurs,

carnosaurs, sauropods.

(Lower Jurassic) 22 my 180-202 mya Feathered dinosaurs

and flying birds.

Triassic 48 my 202-250 mya Early small dinosaurs,

crocodiles, early mammals.

PALEOZOIC (“early life”) 250-544 mya Permian ends with mass

extinction of 95% of all life.

Permian 40 my 250-290 mya Reptiles, mammal-like reptiles.

Carboniferous 290-363 mya Amphibians, insects, spiders.

(Pennsylvanian) 24 my 290-314 mya Giant centipedes & dragonflies.

(Mississipian) 49 my 314-363 mya Onto the land: air-breathing

spiders, scorpions, insects.

Devonian 46 my 363-409 mya Sharks, bony fish. Ends with

extinction of 70% of all species.

Silurian 30 my 409-439 mya Jawless fish, sea scorpions.

Ordovician 439-510 mya Crinoids, snails, nautiloids, trilobites.

(Upper Ordovic.) 25 my 439-464 mya More nautiloids & trilobites.

(Lower Ordovic.) 46 my 464-510 mya Nautiloids, trilobites.

Cambrian 34 my 510-544 mya First multi-celled life: sponges, worms,

corals, jellyfish, trilobites. Weird

creatures of the Burgess Shale.

23

mya

65

mya

99

mya

141

mya

180

mya

202

mya

250

mya

290

mya

314

mya

363

mya

409

mya

439

mya

464

mya

510

mya

now

2. Nature.p65 55 1/14/2004, 3:32 PM