Topic 2: Phylogeny and Diversification of Mammals

Class Mammalia can be divided up into two subclasses

1) Protheria

2)Theria

Protheria

-first beats

-monotremes

Theria

all other mammals

Theria can be divided into two infraclasses

1) Metatheria

2) Eutheria

Metatheria

means changing beats

marsupial mammals

Eutheria

meaning true beasts

placental mammals

The cladistic scheme indicates that marsupual mammals are more closely related to

pplacental mammals than either is to the monortemes.

Subclass Prototheria

-order monotremata

-has two extant suborder: Platypoda, Tachyglossa

Platypoda, platypus

1- one family, ornithorhynchidae

2- one genus, ornithorhynchus

3- one species, ornithorhynchus anatinus

-is a semi-aquatic mammals with a stream-lined body and a duck-like bill

1) the bill is rich in electroreceptors which help it to locate food.

2) they are found in eastern Australia and Tasmania

Tachyglossa, the echidna or spiny anteaters

-one family, Tachyglossidae

-two genera, Tachyglossus and Zaglossus

-four species, one Tachyglossid, and three Zaglossids

Tachyglossus

is a the short beaked echidna

Zaglossus

long beaker echidnas

Echidna

are borrowing insectivores specializing in ants and termites

-covered in spines dorsally which serve a protective role

-found in Australia and New Guinea

Monotremes

posses the basic mammalian features

-are oviparous

• these eggs have leathery shells as seen in many reptile groups

• females do produce milk and care for their young

• mammary glands are simpler in their construction and lack nipples

-endotherms but maintain a much lower metabolish than is found in other mammals.

Monotremes average internal temperature

32C, 90F

Marsupials internal temperature

35C, 95F

Placentals internal temperature

37C, 99F

Subclass: Theria: Infraclass: Metatheria

-marsupial mammals

-geographical distribution is limited to Australasia and the Americas

-share more anatomical and physiological features in common with placental mammals than do monotremes

-gestation time is shorter in marsupials than in comparative placentals

• nourishment is provided during this short gestational period from within the uterus although marsupials have not developed a true placental

• after a short gestation, typically 4 to 5 weeks the offspring will crawl to its mother’s pouch

• if it makes it the offspring will latch on to a nipples in the pouch and complete its development

-there are 334 extanct species and 7 orders

Marsupium

anatomical term for the pouch

Metatheria Orders

1) Didelphimorphia

2)Paucituberculata

3)Microbiotheria

4)Dasyuromorphia

5)Peramelemorphia

6)Notoryctemorphia

7) Diprotodontia

Infraclass Meatheria, Order Didelphimorphia

-American Opossums

87 species

Infraclass Metatheria, order Paucituberculata

• commonly called shrew, or rat, oppossums

• 6 species

infraclass metatheria, order micorbiotheria

one extant species, Monito del monte

infraclass Metatheria, order Dasyuromorphia

a diverse order which includes the extinct Tasmanian wolf, numbat, and dasyures

70 species

infraclass Metatheria, order Peramelemorphia

-bandicoots

21 species

Infraclass metatheria, order Notoryctemorphia

-is a specialized order of burrowers called the marsupial moles

only 2 species

Infraclass metatheria, order Diprotodontia

-diverse order which includes koala, wombats, kangaroos, and most Australian possums

144 species

infraclass metatheria,superorder Australidelphia

• all the orders expect didelphiomorphas are part of this

• consists of all Australasian marsupials, and one American species

it appears that this superorder originated in South America, traveled to Australia by way of Antarctia and then underwent adaptive radiation

Subclass, Theria, Infraclass Eutheria (placentalia)

-are the most successful and widely distributed infraclass of mammals

-found on every continent

-are 20 orders and an estimated 5,077 species

-typically play a major role in the ecosystems that they inhabit and occupy a uniquely broad range of ecological niches

Eutherians unique features

-viviparous

-neonate is fully developed, or almost fully developed when it leaves the uterus

• developing young are kept in the womb until parturition and are supported by a placenta

• have a higher metabolism than do either monotremes or marsupials

• considered to be more intelligent and to be more complex socially/nehaviorally

Placenta

is a well vascularized, temporary structure of the uterus that provides nutrients and oxygen

infraclass eutheria, superorder Afrotheria

-composed of placental mammals that originated in Africa

7 Extant orders of superorder Afrotheria

1) Tubulidentata

2)Afrosocricida

3)Eulipotyphla

4)Macroscelidea

5)Hyracodiea

6)Proboscidea

7)Sirenia

Superorder Afrotheria order Tubulidentata

aardvark

superorder Afrotheria order Afrosoricid

tenreces and golden moles

superorder Afrotheria order Eulipotyphyla

shrews, moles, hedgehogs, gymnures and solenodons

What two orders of superorder Afrotheria were previously grouped in the order Insectivora

-Afrosoricida

-Eulipotyphyla

Superorder Afrotheria, order Macroseclidea

elephant shrews

Superorder Afrotheria, order Hyracodiea

the hyraxs

Superorder Afrotheria, order Proboscidea

elephants

Superorder Afrotheria, order Sirenia

manatees and dugongs

Superorder Xenartha

-represented by anteaters, sloths and armadillos

-evolved in South America

-some migrated into North America when a land bridge (central america) was established later

Two extant orders of Xenartha

1) Cingulata

2)Pilosa

superorder Xenartha, order cingulata

armadillos

superorder xenartha, order pilosa

sloths and anteaters

Superorder Euarchontoglires

-super primates

-superorder is the result of research confirming the evolutionary relationship of two previous superorders, the Euarchonta (primates and allies) and Glires (rodents and allies)

5 extant orders of Euarchontoglires

1) Rodentia

2)Lagomorpha

3)Dermoptera

4)Scandentia

5)Primates

Superorder Euarchontoglires , order Rodentia

rodents (most species rich order)

superorder Euarchontoglires, order lagamorpha

rabbits and hares

super order Euarchontoglires , order dermoptera

culogos, a group of gliding mammals native to southeast asia

superorder Euarchontoglires order scandentia

the three shews

superorder Euarchontoglires, order primates

apes and monkeys

Superorder Laurasiatheria

-large superorder that originated on the Northern supercontinent Laurasia

What superorder originated on Laurasia

Euarchontoglires and Laurasiatheria and are considered to be sistergroups, being more closely related to each other than to either of the two superorders

super order Laurasiatheria 5 extant orders

1) Chiroptera

2)Pholidota

3)Carnivora

4)Cetatriodactlya

5) Per

Superorder Laurasiatheria order chiroptera

bats

second most species rich order

Superorder Laurasiatheria, order Pholidota

the pangolins

superorder Laurasiatheria, order carnivora

cats, dogs, weasel, and bears

What orders do some classification schemes place into the clade Ferae?

Pholidota and Carnivora

Superorder Laurasiatheria order Cettriodactyla

a new order consisting of two previously separates orders

Artiodactyla

Cetacea

Superorder Laurasiatheria order Cettriodactyla- Artiodactyla

the even-toed ungulates such as pigs, goats, antelopes and deer

Superorder Laurasiatheria order Cettriodactyla- Ceteacea

-whales and dolphins

-genetics and fossial evidence indicates that they evolved from an artiodactyl forebearer

• many mammalogists feel that there are enough differences that they should still be considered to be two separate but closely related orders

Superorder Laurasiatheria order Perissodactyla

the odd-toes ungulates such as horses and rhinoceri

What orders do some classification schemes place the two orders into the clase Euungulata?

Cetatriodactyla and Perissodactyla

Timing of Mammalian Radiation

Mammals evolved from a group of retiles called synapsids

Synapsid repitles were distinguished by the fact that their skulls only had

one pair of temporal fossae

temporal fossae

openings on the temporal region of the skull for muscle attachment

Synapsid repitles diverged from other reptiles in the

Carboniferous period

Pelycosaurs

a synapsid group that evolved.

-diverged from other synapsid reptiles around 308 m.y.a

around 275 m.y.a in earyl Permian, the pelycoaurs gave rise to the clade called the therapsids

the therapsid reptiles gave rise to the

Grown group of mammals

Grown group

is a phylogenetic term for a collection of species consisting of the living representative of the group their ancestors, and their common ancestor

Grown group for Mammalia

is all of the descendants from the common ancestor for marsupial and therian lineages

Stem groups

all of the other lineages that diverged before the common ancestor are called this

Eon

Phanerozoic

Era

Paleozocic, Mesozoic, Cenozoic

Paleozoic Periods

Cambrian

Ordovician

silurian

Devonian

Carboniferous

Permian

Periods of Mesozoic

-Triassic

-Jurassic

-Cretaceous

Cenozoic Period

Palgeogene

Neogene

Divergence of the Monotremes

-fossils are rare and the earliest have been identified are from the Cretaceous

-Molecular evidence from various studies indicate that monotremes diverged from therapsids in the Triassic

Best available evidence indicates that Therian mammals diverged from Monotremes

sometime in the Jurassic Period

Origin of the Crown Group Metatherian

-oldest crown group marsupial fossils are from the late Cretaceous

around 65-79 m.y.a

• this would date their origin to close to the Creataceous-Tertiary (KT) boundanry, the period of the great dinosaur extinction event

using molecular data also the range of the potential time period of the origination of the marsupial crown group to 65-84 m.y.a

Diversification of Placental Mammals

-there is some controversy to as when the 20 orders and 4 superorders of placental mammals originated

1) originally it was assumed that the 20 orders became established shortly after the KT boundary around 55 m.y.a

2) however, newly discovered fossila and molecular anaylsis has pushed the hypothertical period for that event up to 90 m.y.a

Although the extinction of the dinosaurs was believed to be a driving factor, since it opened up a number of new niches, some suggest

that the evolution of Angiosperm plants may also have played a role

• this would support the idea for an earlier origination for at least some of the 20 orders