slides for a lecture on the evolution of mammals since the extinction of the dinosaurs, Slides of Biology

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Permian Period

(299 -251 Ma)

Invertebrate marine life rich and diverse  insects evolve; dragonflies & beetles appear Amphibians decline, but reptiles undergo spectacular evolutionary radiation

• Mammal-like reptiles diversify Mass Extinction

http://www.karencarr.com/Images/Gallery/2004_ga

llery_Permian_riverside.jpg

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Triassic Period (251-200 Ma)

• Early dinosaurs evolve.
• Marine reptiles evolve
• Ferns, cycads, ginkgoes, and conifers flourish.
• First mammals ~210 Ma
• Mass extinction ~225 Ma, loss in some groups as much as 75%.

Ceolophysis dinosaurs in

a conifer forest

http://www.pbs.org/wgbh/nova/link/hist_08.html

Jurassic Period (200-146 Ma)

• Reptiles adapt to life in the sea, in the air, and on land
• Dinosaurs dominant reptile on land
• Archaeopteryx , first bird, appears.
• first frogs, toads, and salamanders
• Mammals still small, shrew-like (but!)
• Plant forms dominated by cycads, conifers and gingkoes

http://www.pbs.org/wgbh/nova/link/hist_09.html

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COVER Artist's reconstruction of Castorocauda lutrasimilis diving into water. Castorocauda is an omnivorous mammal from the Middle Jurassic (~164 million years ago) and is the earliest known semi-aquatic animal in the mammalian lineage. See page 1123. Image: Mark A. Klingler, Carnegie Museum of Natural History

Castorocauda lutrasimilis

Semiaquatic mammal

from middle Jurassic of

China

~164 ma

Order: Doconodont

500800 g (~1 lb) largest

mammal of the Jurassic

Multituberculates

(extinct prototherians)

Late Jurassic-Mid. Miocene

(ca. 150 m.y.)

Diverse, found on all continents

Outcompeted to extinction?

(rodents, early primates...)

Cretaceous Period (146 to 65.5 Ma)

• global climate generally warm; poles free of ice.
• dinosaurs dominant vertebrate life form; range on every continent.
• great diversity of invertebrates
• Ammonites, gastropods, corals, sea urchins flourish
• angiosperms arise ~130 Ma and begin to diversify
• Mass extinction

http://www.pbs.org/wgbh/nova/link/hist_10.html

History of the Earth (~ starting dates in millions of years shown parenthetically) Based on ICS 2004

Eras Periods Epochs Aquatic Life Terrestrial Life

Holocene

(.0115) Humans^ in^ NA

Pleistocene

Homo habilis evolves; large forms of mammals

Quaternary

Pliocene (5.3) arctic ice cap forms

Miocene (23) Widespread grasslands

Oligocene

Adaptive radiation of birds

Eocene (55.8)

Cenozoic

“Age of

Mammals” Tertiary

Glacial Cycles (~20) Continent drift

continues Paleocene

All modern groups present Adaptive radiation of mammals; herbaceous angiosperms

Cretaceous

Still attached: NA & N Europe; Australia & Antarctica; shallow seas recede and transgress Modern bony fishes; extinction of ammonites, plesiosaurs, etc. At end, extinction of dinosaurs; rise of woody angiosperms, snakes

Jurassic

At end: Africa & SA begin to drift apart; at end, NA & SA separate; global transgression of shallow seas Plesiosaurs, ichthyosaurs abundant Dinosaurs dominant; 1 st mammals, lizards and angiosperms appear at beginning; insects abundant

Mesozoic

“Age of

Reptiles”

Triassic

Pangaea splits into Laurasia and Gondwana 1 st^ plesiosaurs; ammonites abundant; rise of bony fishes Adaptive radiation of reptiles; therapsids, turtles, crocodiles, 1 st dinosaurs at beginning

Permian

Periodic glaciation; arid climate; at end formation of Pangaea Extinction of trilobites Reptiles abundant; cycads, conifers, ginkgos

Pennsylvanian

Ammonites, bony fishes 1 st (^) reptiles

Mississippian

Warm humid climate; Pennsylvanian and Mississippian together make up the “Carboniferous” or “Age of Amphibians” Adaptive radiation of sharks Forests of lycopsids, seed ferns; amphibitans abundant; land snails

Devonian

“Age of Fishes”

Extensive inland seas Cartilaginous & bony fish; ammonites, nautiloids Ferns, lycopsids, 1 st gymnosperms, 1 st^ insects, first amphibians

Silurian

Mild climate; inland seas; Australian near equator Nautiloids & other molluscs; 1 st jawed fish at end

Ordovician

Mild climate/glaciation; inland seas; most landmasses located in southern or equatorial latitudes Trilobites abundant; 1srt jawless vertebrates 1 st^ fungi and bryophytes; 1 st^ millipedes?

Paleozoic

Cambrian

At beginning, periodic glaciation (leading to lowering of sea level); Gondwana crustaceans, molluscs, echinoderms, sponges, annelids, etc. Lichens, mosses, perhaps some vascular plants? Proterozoic Eon ( 2500 ) Neo^ ,^ M EResoA^ S,^ Paleo^ O snoldewstba^ eukall earrtyoh?ti Stcs^ ro~2m,a^0001 tolit^ e,s^800 dive^ Mra,sif^ Syex,; V^ eMndietaanzoans fauna, Archean Eon ( 4600 ) Neo Meso ERAS Paleo Eo Earth formed; Earliest prokaryotic life at around 3,800 Ma; Stromatolites formed

Most Cretaceous mammals were

terrestrial and ecologically

generalized and occupied a

narrow range of the size spectrum

Mammals were the vermin

of the Mesozoic

“Age of Mammals” “Age of Dinosaurs” K/T boundary K/T boundary

• about 67% of all mammals went extinct at K-T impact
• Paleocene - an immense evolutionary radiation unmatched in mammalian history
• origination rates 5x> than background Alroy 1996, 1998 and unpublished

K/TK/T boundary boundary

Most/all eutherian orders originated & diversify AFTER K/T (traditionally, fossils supported this)