34 vertebrates

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings

PowerPoint Lectures for Biology, Seventh Edition

Neil Campbell and Jane Reece

Lectures by Chris Romero

Chapter 34Chapter 34

Vertebrates


• Overview: Half a Billion Years of Backbones

• By the end of the Cambrian period, some 540 million years ago

– An astonishing variety of animals inhabited Earth’s oceans

• One of these types of animals

– Gave rise to vertebrates, one of the most successful groups of animals


• The animals called vertebrates

– Get their name from vertebrae, the series of bones that make up the backbone

Figure 34.1


• There are approximately 52,000 species of vertebrates

– Which include the largest organisms ever to live on the Earth


• Concept 34.1: Chordates have a notochord and a dorsal, hollow nerve cord

• Vertebrates are a subphylum of the phylum Chordata

• Chordates are bilaterian animals

– That belong to the clade of animals known as Deuterostomia

• Two groups of invertebrate deuterostomes, the urochordates and cephalochordates

– Are more closely related to vertebrates than to invertebrates


• A hypothetical phylogeny of chordatesChordates

CraniatesVertebrates

GnathostomesOsteichthyans

Lobe-finsTetrapods

Amniotes

Milk

Amniotic egg

Legs

Lobed fins

Lungs or lung derivatives

Jaws, mineralized skeleton

Vertebral column

Head

Brain

Notochord

Ancestral deuterostome

Ech

ino

de

rmat

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rou

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tes)

Uro

ch

ord

ata

(tu

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tes)

Ce

ph

alo

ch

ord

ata

(lan

cele

ts)

Myx

ini

(hag

fish

es)

Ce

ph

ala

spid

om

orp

hi

(lam

pre

ys)

Ch

on

dri

ch

thy

es(s

hark

s, r

ays

, ch

ima

era

s)

Ac

tin

op

tery

gii

(ray

-fin

ned

fish

es)

Ac

tin

isti

a(c

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can

ths)

Dip

no

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ungf

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Am

ph

ibia

(fro

gs,

sala

man

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Re

pti

lia

(tu

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nak

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croc

odi

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bird

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Mam

mal

ia(m

amm

als)

Figure 34.2


Derived Characters of Chordates

• All chordates share a set of derived characters

– Although some species possess some of these traits only during embryonic development

Musclesegments

Brain

Mouth

Anus

Dorsal,hollow

nerve cord

Notochord

Muscular,post-anal tail

Pharyngealslits or clefts

Figure 34.3


Notochord

• The notochord

– Is a longitudinal, flexible rod located between the digestive tube and the nerve cord

– Provides skeletal support throughout most of the length of a chordate

• In most vertebrates, a more complex, jointed skeleton develops

– And the adult retains only remnants of the embryonic notochord


Dorsal, Hollow Nerve Cord

• The nerve cord of a chordate embryo

– Develops from a plate of ectoderm that rolls into a tube dorsal to the notochord

– Develops into the central nervous system: the brain and the spinal cord


Pharyngeal Slits or Clefts

• In most chordates, grooves in the pharynx called pharyngeal clefts

– Develop into slits that open to the outside of the body

• These pharyngeal slits

– Function as suspension-feeding structures in many invertebrate chordates

– Are modified for gas exchange in aquatic vertebrates

– Develop into parts of the ear, head, and neck in terrestrial vertebrates


Muscular, Post-Anal Tail

• Chordates have a tail extending posterior to the anus

– Although in many species it is lost during embryonic development

• The chordate tail contains skeletal elements and muscles

– And it provides much of the propelling force in many aquatic species


Tunicates

• Tunicates, subphylum Urochordata

– Belong to the deepest-branching lineage of chordates

– Are marine suspension feeders commonly called sea squirts


Figure 34.4c

• Tunicates most resemble chordates during their larval stage

– Which may be as brief as a few minutes

Pharynx with slits

Notochord

Tail

Dorsal, hollownerve cord

AtriumStomach

Intestine

Excurrent siphon

Incurrentsiphon

Musclesegments

(c) A tunicate larva is a free-swimming butnonfeeding “tadpole” in which all fourchief characters of chordates are evident.


• As an adult

– A tunicate draws in water through an incurrent siphon, filtering food particles

(a) An adult tunicate, or sea squirt, is a sessile animal (photo is approximately life-sized).

(b) In the adult, prominent pharyngeal slits function in suspension feeding, but other chordate characters are not obvious.

Tunic

Pharynxwith

numerousslits

Atrium

Excurrentsiphon

Incurrentsiphonto mouth

StomachEsophagus

IntestineAnus

Excurrent siphon

Figure 34.4a, b


Lancelets

• Lancelets, subphylum Cephalochordata

– Are named for their bladelike shape

Tentacle

Mouth

Pharyngeal slits

Atrium

Digestive tract

Atriopore

Segmentalmuscles

Anus

Notochord

Dorsal, hollownerve cord

Tail

2 cm

Figure 34.5


• Lancelets are marine suspension feeders

– That retain the characteristics of the chordate body plan as adults


Early Chordate Evolution

• The current life history of tunicates

– Probably does not reflect that of the ancestral chordate


• Gene expression in lancelets

– Holds clues to the evolution of the vertebrate formBF1

BF1Otx

Otx Hox3

Hox3

Forebrain

Midbrain

Hindbrain

Nerve cord of lancelet embryo

Brain of vertebrate embryo(shown straightened)

Figure 34.6


• Concept 34.2: Craniates are chordates that have a head

• The origin of a head

– Opened up a completely new way of feeding for chordates: active predation

• Craniates share some common characteristics

– A skull, brain, eyes, and other sensory organs


Derived Characters of Craniates

• One feature unique to craniates

– Is the neural crest, a collection of cells that appears near the dorsal margins of the closing neural tube in an embryo

Notochord

(a) The neural crest consists of bilateral bands of cells near the margins of the embryonic folds that form the neural tube.

(b) Neural crest cells migrate todistant sites in the embryo.

Migrating neuralcrest cells

Ectoderm

Ectoderm

Dorsal edgesof neural plate

Neuralcrest

Neuraltube

Figure 34.7a, b


• Neural crest cells

– Give rise to a variety of structures, including some of the bones and cartilage of the skull

(c) The cells give rise to some of the anatomical structuresunique to vertebrates, including some of the bones and cartilage of the skull.

Figure 34.7c


The Origin of Craniates

• Craniates evolved at least 530 million years ago

– During the Cambrian explosion


• The most primitive of the fossils

– Are those of the 3-cm-long Haikouella

Figure 34.8a

(a) Haikouella. Discovered in 1999 in southern China, Haikouella had eyes and a brain but lacked a skull, a derived trait of craniates.


• In other Cambrian rocks

– Paleontologists have found fossils of even more advanced chordates, such as Haikouichthys

Figure 34.8b

(b) Haikouichthys. Haikouichthys had a skull and thus is considered a true craniate.

5 mm


Hagfishes

• The least derived craniate lineage that still survives

– Is class Myxini, the hagfishes

Figure 34.9

Slime glands


• Hagfishes are jawless marine craniates

– That have a cartilaginous skull and axial rod of cartilage derived from the notochord

– That lack vertebrae


• Concept 34.3: Vertebrates are craniates that have a backbone

• During the Cambrian period

– A lineage of craniates evolved into vertebrates


Derived Characters of Vertebrates

• Vertebrates have

– Vertebrae enclosing a spinal cord

– An elaborate skull

– Fin rays, in aquatic forms


Lampreys

• Lampreys, class Cephalaspidomorphi

– Represent the oldest living lineage of vertebrates

– Have cartilaginous segments surrounding the notochord and arching partly over the nerve cord


• Lampreys are jawless vertebrates

– Inhabiting various marine and freshwater habitats

Figure 34.10


Fossils of Early Vertebrates

• Conodonts were the first vertebrates

– With mineralized skeletal elements in their mouth and pharynx

Dorsal viewof head

DentalelementsFigure 34.11


• Armored, jawless vertebrates called ostracoderms

– Had defensive plates of bone on their skin

Pteraspis

Pharyngolepis

Figure 34.12


Origins of Bone and Teeth

• Mineralization

– Appears to have originated with vertebrate mouthparts

• The vertebrate endoskeleton

– Became fully mineralized much later


• Concept 34.4: Gnathostomes are vertebrates that have jaws

• Today, jawless vertebrates

– Are far outnumbered by those with jaws


Derived Characters of Gnathostomes

• Gnathostomes have jaws

– That evolved from skeletal supports of the pharyngeal slits

Mouth

Gill slits Cranium

Skeletal rods

Figure 34.13


• Other characters common to gnathostomes include

– Enhanced sensory systems, including the lateral line system

– An extensively mineralized endoskeleton

– Paired appendages


Fossil Gnathostomes

• The earliest gnathostomes in the fossil record

– Are an extinct lineage of armored vertebrates called placoderms

Figure 34.14a

(a) Coccosteus, a placoderm


• Another group of jawed vertebrates called acanthodians

– Radiated during the Devonian period

– Were closely related to the ancestors of osteichthyans

Figure 34.14b

(b) Climatius, an acanthodian


Chondrichthyans (Sharks, Rays, and Their Relatives)

• Members of class Chondrichthyes

– Have a skeleton that is composed primarily of cartilage

• The cartilaginous skeleton

– Evolved secondarily from an ancestral mineralized skeleton


• The largest and most diverse subclass of Chondrichthyes

– Includes the sharks and rays

Figure 34.15a, b

Pectoral fins Pelvic fins

(a) Blacktip reef shark (Carcharhinus melanopterus). Fast swimmers with acute senses, sharks have paired pectoral and pelvic fins.

(b) Southern stingray (Dasyatis americana). Most rays are flattened bottom-dwellers thatcrush molluscs and crustaceans for food. Some rays cruise in open water and scoop food into their gaping mouth.


• A second subclass

– Is composed of a few dozen species of ratfishes

Figure 34.15c

(c) Spotted ratfish (Hydrolagus colliei). Ratfishes, or chimaeras, typically live at depths greaterthan 80 m and feed on shrimps, molluscs, and sea urchins. Some species have a poisonous spine at the front of their dorsal fin.


• Most sharks

– Have a streamlined body and are swift swimmers

– Have acute senses


Ray-Finned Fishes and Lobe-Fins

• The vast majority of vertebrates

– Belong to a clade of gnathostomes called Osteichthyes


• Nearly all living osteichthyans

– Have a bony endoskeleton

• Aquatic osteichthyans

– Are the vertebrates we informally call fishes

– Control their buoyancy with an air sac known as a swim bladder


• Fishes breathe by drawing water over four or five pairs of gills

– Located in chambers covered by a protective bony flap called the operculum

Nostril Brain

Spinal cordSwim bladder

Dorsal fin Adipose fin(characteristic oftrout)

Caudal fin

Cut edge of operculum Gills

HeartLiver

KidneyStomach

Intestine

GonadAnus

Urinary bladder

Lateral line

Anal fin

Pelvic finFigure 34.16


Ray-Finned Fishes

• Class Actinopterygii, the ray-finned fishes

– Includes nearly all the familiar aquatic osteichthyans

(a) Yellowfin tuna (Thunnus albacares), a fast-swimming, schooling fish that is an important commercial fish worldwide

(b) Clownfish (Amphiprion ocellaris), a mutualistic symbiont of sea anemones

(c) Sea horse (Hippocampus ramulosus), unusual in the animal kingdom in that the male carries the young during their embryonic development

(d) Fine-spotted moray eel (Gymnothorax dovii), a predator that ambushes prey from crevices in its coral reef habitatFigure 34.17a–d


• The fins, supported mainly by long, flexible rays

– Are modified for maneuvering, defense, and other functions


Lobe-Fins

• The lobe-fins, class Sarcopterygii

– Have muscular and pectoral fins

– Include coelacanths, lungfishes, and tetrapods

Figure 34.18


• Concept 34.5: Tetrapods are gnathostomes that have limbs and feet

• One of the most significant events in vertebrate history

– Was when the fins of some lobe-fins evolved into the limbs and feet of tetrapods


Derived Characters of Tetrapods

• Tetrapods have some specific adaptations

– Four limbs and feet with digits

– Ears for detecting airborne sounds


The Origin of Tetrapods

• In one lineage of lobe-fins

– The fins became progressively more limb-like while the rest of the body retained adaptations for aquatic life

Tetrapodlimbskeleton

Bonessupportinggills

Figure 34.19


• Extraordinary fossil discoveries over the past 20 years

– Have allowed paleontologists to reconstruct the origin of tetrapods

Figure 34.20Amniotes

Amphibians

GreerpetonHynerpeton

lchthyostega

Acanthostega

Metaxygnathus

Elginerpeton

Eusthenopteron

Panderichthys

Lungfishes

Coelacanths

Ray-finned fishes

Paleozoic

Silurian Devonian Carboniferous Permian To present

420 415 400 385 370 355 340 325 310 295 280 265

Millions of years ago


Amphibians

• Class Amphibia

– Is represented by about 4,800 species of organisms

• Most amphibians

– Have moist skin that complements the lungs in gas exchange


• Order Urodela

– Includes salamanders, which have tails

Figure 34.21a

(a) Order Urodela. Urodeles (salamanders) retain their tail as adults.


• Order Anura

– Includes frogs and toads, which lack tails

Figure 34.21b

(b) Order Anura. Anurans, such as this poison arrow frog, lack a tail as adults.


• Order Apoda

– Includes caecilians, which are legless and resemble worms

Figure 34.21c

(c) Order Apoda. Apodans, or caecilians, are legless, mainly burrowing amphibians.


• Amphibian means “two lives”

– A reference to the metamorphosis of an aquatic larva into a terrestrial adult

Figure 34.22a–c

(a) The male grasps the female, stimulating her to release eggs. The eggs are laid and fertilized in water. They have a jelly coat but lack a shell and would desiccate in air.

(b) The tadpole is an aquatic herbivore witha fishlike tail and internal gills.

(c) During metamorphosis, the gills and tail are resorbed, andwalking legs develop.


• Concept 34.6: Amniotes are tetrapods that have a terrestrially adapted egg

• Amniotes are a group of tetrapods

– Whose living members are the reptiles, including birds, and the mammals


• A phylogeny of amniotes

Figure 34.23

Synapsids

Ancestralamniote

Reptiles

Diapsids

Archosaurs

Saurischians

Lepidosaurs

Dinosaurs

Par

arep

tiles

Turt

les

Cro

codi

lians

Pte

rosa

urs

Orn

ithis

chia

ndi

nosa

urs

Sau

risch

ian

dino

saur

s ot

her

than

bird

s

Bir

ds

Ple

sios

aurs

Icht

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aurs

Tuat

ara

Squ

amat

esM

amm

als


Derived Characters of Amniotes

• Amniotes are named for the major derived character of the clade, the amniotic egg

– Which contains specialized membranes that protect the embryo


• The extraembryonic membranes

– Have various functions

Figure 34.24Shell

Albumen

Yolk (nutrients)

Amniotic cavitywith amniotic fluid

Embryo

Yolk sac. The yolk sac contains the yolk, a stockpile of nutrients. Blood vessels in the yolk sac membrane transport nutrients from the yolk into the embryo. Other nutrients are stored in the albumen (“egg white”).

Allantois. The allantois is a disposalsac for certain metabolic wastes pro-duced by the embryo. The membraneof the allantois also functions withthe chorion as a respiratory organ.

Amnion. The amnion protectsthe embryo in a fluid-filled cavity that cushions againstmechanical shock.

Chorion. The chorion and the membrane of the allantois exchange gases between the embryo and the air. Oxygen and carbon dioxide diffuse freely across the shell.

Extraembryonic membranes


• Amniotes also have other terrestrial adaptations

– Such as relatively impermeable skin and the ability to use the rib cage to ventilate the lungs


Early Amniotes

• Early amniotes

– Appeared in the Carboniferous period

– Included large herbivores and predators


Reptiles

• The reptile clade includes

– The tuatara, lizards, snakes, turtles, crocodilians, birds, and the extinct dinosaurs


• Reptiles

– Have scales that create a waterproof barrier

– Lay shelled eggs on land

Figure 34.25


• Most reptiles are ectothermic

– Absorbing external heat as the main source of body heat

• Birds are endothermic

– Capable of keeping the body warm through metabolism


The Origin and Evolutionary Radiation of Reptiles

• The oldest reptilian fossils

– Date to about 300 million years ago

• The first major group of reptiles to emerge

– Were the parareptiles, which were mostly large, stocky herbivores


• As parareptiles were dwindling

– The diapsids were diversifying

• The diapsids are composed of two main lineages

– The lepidosaurs and the archosaurs


• The dinosaurs

– Diversified into a vast range of shapes and sizes

– Included the long-necked giants called the theropods


Figure 34.26

• Traditionally, dinosaurs were considered slow, sluggish creatures

– But fossil discoveries and research have led to the conclusion that dinosaurs were agile and fast moving

• Paleontologists have also discovered signs of parental care among dinosaurs


Lepidosaurs

• One surviving lineage of lepidosaurs

– Is represented by two species of lizard-like reptiles called tuatara

Figure 34.27a (a) Tuatara (Sphenodon punctatus)


Figure 34.27b(b) Australian thorny devil lizard (Moloch horridus)

• The other major living lineage of lepidosaurs

– Are the squamates, the lizards and snakes

• Lizards

– Are the most numerous and diverse reptiles, apart from birds


• Snakes are legless lepidosaurs

– That evolved from lizards

Figure 34.27c

(c) Wagler’s pit viper (Tropidolaemus wagleri), a snake


Turtles

• Turtles

– Are the most distinctive group of reptiles alive today

• Some turtles have adapted to deserts

– And others live entirely in ponds and rivers


• All turtles have a boxlike shell

– Made of upper and lower shields that are fused to the vertebrae, clavicles, and ribs

Figure 34.27d (d) Eastern box turtle (Terrapene carolina carolina)


Alligators and Crocodiles

• Crocodilians

– Belong to an archosaur lineage that dates back to the late Triassic

Figure 34.27e (e) American alligator (Alligator mississipiensis)


Birds

• Birds are archosaurs

– But almost every feature of their reptilian anatomy has undergone modification in their adaptation to flight


Derived Characters of Birds

• Many of the characters of birds

– Are adaptations that facilitate flight


• A bird’s most obvious adaptations for flight

– Are its wings and feathers

Figure 34.28a–c

(a) wing

(b) Bone structure

Finger 1

(c) Feather structure

Shaft

BarbBarbule

Hook

Vane

Shaft

ForearmWrist

Palm

Finger 3

Finger 2


The Origin of Birds

• Birds probably descended from theropods

– A group of small, carnivorous dinosaurs


• By 150 million years ago

– Feathered theropods had evolved into birds

• Archaeopteryx

– Remains the oldest bird known

Figure 34.29

Toothed beak

Airfoil wing with contour feathers

Long tail with many vertebrae

Wing claw


Living Birds

• The ratites, order Struthioniformes

– Are all flightless

Figure 34.30a

(a) Emu. This ratite lives in Australia.


• The demands of flight

– Have rendered the general body form of many flying birds similar to one another

Figure 34.30b–d

(b) Mallards. Like many bird species, the mallard exhibits pronounced color differences between the sexes.

(c) Laysan albatrosses. Like most birds, Laysan albatrosses have specific mating behaviors, such as this courtship ritual.

(d) Barn swallows. The barn swallow is a member of the order Passeriformes. Species in this order are called perching birds because the toes of their feet can lock around a branch or wire, enabling the bird to rest in place for long periods.


• Foot structure in bird feet

– Shows considerable variation

Figure 34.31

Grasping bird (such as a woodpecker)

Perching bird (such as a cardinal)

Raptor(such as a bald eagle)

Swimming bird(such as a duck)


• Concept 34.7: Mammals are amniotes that have hair and produce milk

• Mammals, class Mammalia

– Are represented by more than 5,000 species


Derived Characters of Mammals

• Mammary glands, which produce milk

– Are a distinctively mammalian character

• Hair is another mammalian characteristic

• Mammals generally have a larger brain

– Than other vertebrates of equivalent size


Early Evolution of Mammals

• Mammals evolved from synapsids

– In the late Triassic period


• The jaw was remodeled during the evolution of mammals from nonmammalian synapsids

– And two of the bones that formerly made of the jaw joint were incorporated into the mammalian middle ear

Sound Sound

Jaw joint Jaw joint Key

DentaryAngularSquamosal

ArticularQuadrate

Dimetrodon Morganucodon

Dimetrodon Morganucodon

Eardrum

Eardrum Middle ear Middle earStapes Inner ear

Inner ear

Stapes

Incus (evolvedfrom quadrate)

Malleus (evolvedfrom articular)

(b) During the evolutionary remodeling of the mammalian skull, the quadrate and articular bones became incorporated into the middle ear as two of the three bones that transmit sound from the eardrum to the inner ear. The steps in this evolutionary remodeling are evident in a succession of fossils.

(a) The lower jaw of Dimetrodon is composed of several fused bones; two small bones, the quadrate and articular, form part of the jaw joint. In Morganucodon, the lower jaw is reduced to a single bone, the dentary, and the location of the jaw joint has shifted.

Figure 34.32a, b


• Living lineages of mammals originated in the Jurassic

– But did not undergo a significant adaptive radiation until after the Cretaceous


Monotremes

• Monotremes

– Are a small group of egg-laying mammals consisting of echidnas and the platypus

Figure 34.33


Marsupials

• Marsupials

– Include opossums, kangaroos, and koalas


• A marsupial is born very early in its development

– And completes its embryonic development while nursing within a maternal pouch called a marsupium

Figure 34.34a

(a) A young brushtail possum. The young of marsupials are born very early in their development. They finish their growth while nursing from a nipple (in their mother’s pouch in most species).


• In some species of marsupials, such as the bandicoot

– The marsupium opens to the rear of the mother’s body as opposed to the front, as in other marsupials

Figure 34.34b

(b) Long-nosed bandicoot. Most bandicoots are diggers and burrowers that eat mainly insects but also some small vertebrates andplant material. Their rear-opening pouch helps protect the young from dirt as the mother digs. Other marsupials, such as kangaroos, have a pouch that opens to the front.


• In Australia, convergent evolution

– Has resulted in a diversity of marsupials that resemble eutherians in other parts of the world

Figure 34.35

Marsupial mammals Eutherian mammals

Plantigale

Marsupial mole

Sugar glider

Wombat

Tasmanian devil

Kangaroo

Deer mouse

Mole

Woodchuck

Flying squirrel

Wolverine

Patagonian cavy


Eutherians (Placental Mammals)

• Compared to marsupials

– Eutherians have a longer period of pregnancy

• Young eutherians

– Complete their embryonic development within a uterus, joined to the mother by the placenta


• Phylogenetic relationships of mammals

Figure 34.36

Ancestral mammal

Monotremes Marsupials Eutherians

Monotremata Marsupialia Xenarthra

Proboscidea SireniaTubulidentata Hyracoidea Afrosoricida (golden moles and tenrecs)Macroscelidea (elephant shrews)

RodentiaLagomorphaPrimatesDermoptera (flying lemurs)Scandentia (tree shrews)

CarnivoraCetartiodactylaPerissodactylaChiropteraEulipotyphlaPholidota (pangolins)

Possible phylogenetic tree of mammals. All 20 extant orders of mammals are listed at the top of the tree. Boldfaced orders are explored on the facing page.

This diverse clade includes terrestrial and marine mammals as well as bats,the only flying mammals. A growingbody of evidence, including Eocene fossils of whales with feet,supports putting whales inthe same order (Cetartiodactyla) as pigs, cows, and hippos.

This is the largest eutherian clade. It includes the rodents, which make up the largest mammalian order by far, with about 1,770 species. Humansbelong to the order Primates.

All members of this clade, which underwent an adaptive radiation in South America, belong to the order Xenarthra. One species, the nine-banded armadillo, is found in the southern United States.

This clade of eutherians evolved in Africa when the continent was isolated from other landmasses. It includesEarth’s largest living land animal (the African elephant), as well as species that weighless than 10 g.


• The major eutherian orders

Figure 34.36

ORDERSAND EXAMPLES

MAIN CHARACTERISTICS

Monotremata Platypuses, echidnas

Proboscidea Elephants

SireniaManatees,dugongs

CetartiodactylaArtiodactylsSheep, pigs cattle, deer,giraffes

Lagomorpha Rabbits, hares, picas

Carnivora Dogs, wolves,bears, cats, weasels, otters,seals, walruses

Xenarthra Sloths, anteaters,armadillos

CetaceansWhales,dolphins,porpoises

Echidna

African elephant

Manatee

Tamandua

Jackrabbit

Coyote

Bighorn sheep

Pacific white-sided porpoise

Lay eggs; nonipples; young suck milk fromfur of mother

Long, musculartrunk; thick, loose skin; upper incisors elongated as tusks

Aquatic; finlikeforelimbs and no hind limbs; herbivorous

Reduced teeth orno teeth; herbivorous(sloths) or carnivorous (anteaters, armadillos)

Chisel-like incisors; hind legs longer than forelegs and adapted for running and jumping

Sharp, pointed canineteeth and molars for shearing; carnivorous

Hooves with an even number of toes on each foot; herbivorous

Aquatic; streamlinedbody; paddle-like forelimbs and no hind limbs; thicklayer of insulating blubber; carnivorous

Diet consists mainly of insects and other small invertebrates

Adapted for flight; broad skinfold that extends from elongated fingers to body and legs; carnivorous or herbivorous

Hooves with an odd number of toeson each foot; herbivorous

Opposable thumbs; forward-facing eyes; well-developed cerebral cortex; omnivorous

Chisel-like, continuously growing incisors worn down by gnawing;herbivorous

Short legs; stumpy tail; herbivorous; complex, multichamberedstomach

Teeth consisting of many thin tubes cemented together; eats ants and termites

Embryo completes development in pouch on mother

ORDERSAND EXAMPLES

MAIN CHARACTERISTICS

MarsupialiaKangaroos,opossums,koalas

TubulidentataAardvark

HyracoideaHyraxes

ChiropteraBats

PrimatesLemurs,monkeys,apes,humans

PerissodactylaHorses,zebras, tapirs,rhinoceroses

RodentiaSquirrels,beavers, rats, porcupines,mice

Eulipotyphla“Core insecti-vores”: some moles, some shrews Star-nosed

mole

Frog-eating bat

Indian rhinoceros

Golden lion tamarin

Red squirrel

Rock hyrax

Aardvark

Koala


Primates

• The mammalian order Primates include

– Lemurs, tarsiers, monkeys, and apes

• Humans are members of the ape group


Derived Characters of Primates

• Most primates

– Have hands and feet adapted for grasping

• Primates also have

– A large brain and short jaws

– Forward-looking eyes close together on the face, providing depth perception

– Well-developed parental care and complex social behavior

– A fully opposable thumb


Living Primates

• There are three main groups of living primates

– The lemurs of Madagascar and the lorises and pottos of tropical Africa and southern Asia

Figure 34.37


– The tarsiers of Southeast Asia

– The anthropoids, which include monkeys and hominids worldwide


• The oldest known anthropoid fossils, about 45 million years old

– Indicate that tarsiers are more closely related to anthropoids

Figure 34.3860

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• The fossil record indicates that monkeys

– First appeared in the New World (South America) during the Oligocene

• The first monkeys

– Evolved in the Old World (Africa and Asia)


• New World and Old World monkeys

– Underwent separate adaptive radiations during their many millions of years of separation

Figure 34.39a, b

(a) New World monkeys, such as spider monkeys (shown here), squirrel monkeys, and capuchins, have a prehensile tail and nostrils that open to the sides.

(b) Old World monkeys lack a prehensile tail, and their nostrils open downward. This group includes macaques (shown here), mandrills, baboons, and rhesus monkeys.


• The other group of anthropoids, the hominoids

– Consists of primates informally called apes

Figure 34.40a–e

(a) Gibbons, such as this Muller's gibbon, are found only in southeastern Asia. Their very long arms and fingers are adaptations for brachiation.

(b) Orangutans are shy, solitary apes that live in the rain forests of Sumatra and Borneo. They spend most of their time in trees; note the foot adapted for grasping and the opposable thumb.

(c) Gorillas are the largest apes: some males are almost 2 m tall and weigh about 200 kg. Found only in Africa, these herbivores usually live in groups of up to about 20 individuals.

(d) Chimpanzees live in tropical Africa. They feed and sleep in trees but also spend a great deal of time on the ground. Chimpanzees are intelligent, communicative, and social.

(e) Bonobos are closely related to chimpanzees but are smaller. They survive today only in the African nation of Congo.


• Hominoids

– Diverged from Old World monkeys about 20–25 million years ago


• Concept 34.8: Humans are bipedal hominoids with a large brain

• Homo sapiens is about 160,000 years old

– Which is very young considering that life has existed on Earth for at least 3.5 billion years


Derived Characters of Hominids

• A number of characters distinguish humans from other hominoids

– Upright posture and bipedal locomotion

– Larger brains

– Language capabilities

– Symbolic thought

– The manufacture and use of complex tools

– Shortened jaw


The Earliest Humans

• The study of human origins

– Is known as paleoanthropology


• Paleoanthropologists have discovered fossils of approximately 20 species of extinct hominoids

– That are more closely related to humans than to chimpanzees


• These species are known as hominids

Figure 34.41

Homosapiens

Homoneanderthalensis

Homoergaster

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Homohabilis

Homorudolfensis

Paranthropusrobustus

Paranthropusboisei

Australopithecusgarhi

Australopithecusafricanus

Australopithecusafarensis

Kenyanthropusplatyops

Australopithecusanamensis

Ardipithecusramidus

Orrorin tugenensis

Sahelanthropustchadensis

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• Hominids originated in Africa

– Approximately 6–7 million years ago

• Early hominids

– Had a small brain, but probably walked upright, exhibiting mosaic evolution


• Two common misconceptions of early hominids include

– Thinking of them as chimpanzees

– Imagining human evolution as a ladder leading directly to Homo sapiens


Australopiths

• Australopiths are a paraphyletic assemblage of hominids

– That lived between 4 and 2 million years ago


• Some species walked fully erect

– And had human-like hands and teeth

Figure 34.42a–c

(a) Lucy, a 3.24-million-year-old skeleton, represents the hominid species Australopithecus afarensis.

(b) The Laetoli footprints, more than 3.5 million years old, confirm that upright posture evolved quite early in hominid history.

(c) An artist’s reconstruction of what A. afarensis may have looked like.


Bipedalism

• Hominids began to walk long distances on two legs

– About 1.9 million years ago


Tool Use

• The oldest evidence of tool use—cut marks on animal bones

– Is 2.5 million years old


Early Homo

• The earliest fossils that paleoanthropologists place in our genus Homo

– Are those of the species Homo habilis, ranging in age from about 2.4 to 1.6 million years

• Stone tools have been found with H. habilis

– Giving this species its name, which means “handy man”


• Homo ergaster

– Was the first fully bipedal, large-brained hominid

– Existed between 1.9 and 1.6 million years

Figure 34.43


• Homo erectus

– Originated in Africa approximately 1.8 million years ago

– Was the first hominid to leave Africa


Neanderthals

• Neanderthals, Homo neanderthalensis

– Lived in Europe and the Near East from 200,000 to 30,000 years ago

– Were large, thick-browed hominids

– Became extinct a few thousand years after the arrival of Homo sapiens in Europe


Homo sapiens

• Homo sapiens

– Appeared in Africa at least 160,000 years ago

Figure 34.44


• The oldest fossils of Homo sapiens outside Africa

– Date back about 50,000 years ago


• The rapid expansion of our species

– May have been preceded by changes to the brain that made symbolic thought and other cognitive innovations possible

Figure 34.45

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