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

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

Living Birds

• The ratites, order Struthioniformes

– Are all flightless

• The demands of flight

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

• Foot structure in bird feet

– Shows considerable variation

Mammals

• Developed from latest Late Triassic synapsids

– remained mouse-sized

– did not compete with dinosaurs in their niches

• developed mammary glands

• endothermic and homothermic--required high food intake

• jaw muscles and teeth well adapted for catching prey

• soft palate to separate breathing from eating passages

Mammals

– mid-Cretaceous divergence into two groups

• placentals (young carried in uterus until ready for birth)

• marsupials (pouched mammals)

– young crawl to pouch to finish development

» oppossum, kangaroo, koala, etc.

• Mammals are amniotes that have hair and produce milk

• Mammals, class Mammalia

– Are represented by more than 5,000 species

• .  The earliest mammals evolved from reptiles about 220 million years ago.  Therapsids gave rise to mammals.  

.  Major groups of mammals:

•

• a.  Monotremes – lay eggs and produce milk, but have no nipples.

• - Platypus, echidna            

• b.  Marsupials – born early in embryonic development; climb to mother’s pouch and attach to a nipple.

• - Opossum, kangaroo 

•

• c.  Eutherians – long pregnancy with embryonic attachment to mother in uterus via placenta

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

• Living lineages of mammals originated in the Jurassic

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

• Mammals

• Mammals appeared in the Triassic period, as part of a lineage of small, nocturnal therapsids. The feature distinguishing them was the transformation of the the quadrate and articular bones to the incus and malleus.

• -Mammalian characteristics acquired before transition to true mammals:

• -Endothermy? (as indicated by turbinate bones)

• -Mammalian gait (limbs tucked under body)

• -Mammalian characteristics that could have appeared before the transition to mammals:

• -Hair (as insulation for endothermy, and for sensation by touch at night)

•

• -Lactation (signs of lips in some pre-mammalian therapsids; supply of high-energy food for endothermic young)

• -Increase in size of cerebral cortex (associated with olfaction in nocturnal animals)

• -Appearing after the transition:

• -Viviparity

While mammals persisted throughout the Mesozic era (the “Age of Reptiles”), they were not the dominant large land animals. Some of the major lineages of mammals appeared during this time.

• -Monotremes are egg-laying mammals, but they produce milk – in a slit. Young lap milk.

• -Marsupials are viviparous, but young are born poorly-developed, and depend on lacatation for nourishment as they develop. The young suck milk.

• Our lucky stars.

• Strong evidence for a large extraterrestrial impact on earth 65 million years ago, marking the end of the Cretaceous period.

• -Probably the cause of mass extinctions at this time, including the dinosaurs (except birds)

• -This may have allowed the diversification of mammals as the predominant large land animals.

Monotremes and Marsupials

Monotremes

• Monotremes

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

Monotremata (mon-uh-TREEM-ah-tuh)

• Prototheria, (pro¯’to¯-thîr’e¯-Qnz ) retention of various reptilian features

• Two families:

• Ornithorhynchidae (OR-nith-oh-RIN-kuh-dee) and Tachyglossidae (TAK-ih-GLOS-suh-dee )

• Monotremata = “one opening”

– Cloaca, common opening of fecal, urinary and reproductive tracts

• Rubbery-shelled eggs (permeable)

Monotremata con’t

• Eggs are small, incubated for 10 to 11 days

• Neonates have well developed forelimbs and shoulders

Monotremata con’t

• No teats

• Pectoral girdle has coracoid, precoracoid, and interclavicle bone (similar to Therapsid reptile)

• Homeotherm - low - 32 C

• Sperm are fiiform (threadlike) and testis structures similar to reptile

Pectoral girdle

Ornithorhynchidae
OR-nith-oh-RIN-kuh-dee

• Duck-billed platypus

• Semiaquatic, semifossorial

• Near freshwater lakes and rivers, east coast of Australia and Tasmania

• Feed on invert., fish and amphibians

• Adult male 1.7 kg, female smaller

• Short dense fur covers all but bill, feet, and underside of tail

• Bill is soft and pliable, with nostrils at tip

– Has tactile receptors to sense electric field generated by muscle contraction of prey

Ornithorhynchidae con’t

• Has small eyes and ears

• Pentadactyle (five-toed) and manus (forefoot) is webbed

• Long claws for digging burrow

Ornithorhynchidae con’t

• Spur on hind limb connect to venom gland in thigh

• Platypus has no pouch, female incubate eggs in burrow

• Neonates have molariform teeth, shed before emerge from burrow

– Keratinized pads

• Milk is secreted onto tufts of hair

Ornithorhynchidae con’t

Tachyglossidae

• Short-beaked echidna (Tachyglossus)

– Australia, New Guinea, and Tasmania

– 6 kg

• Long-beaked echidna (Zaglossus)

– Forested highland of New Guinea

– 10 kg

• Feed on ants, termites, and insects - ground to paste between tongue and spiny palatal ridge

• Have scooplike claws on feet to break anthills and burrows

• Ankle spur not venomous

Tachyglossidae con’t

• Beak contains electroreceptors

• Guard hairs modified to become spines

• Mucus that coat tongue to make it sticky

• No teeth at any stage of development

• Have a pouch for incubating eggs

Marsupials

• Characterized by marsupium

– Only 50% of species have permanent pouch

• Litters that weigh 1% of mother’s body mass

– Eutherians: litters weigh 50% of mother’s BM

• Have well-developed stylar shelf

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

• 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

• In Australia, convergent evolution

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

Marsupials con’t

• Lower basal metabolic rate (BMR) - 70% of comparable sized eutherians

• Slower postnatal growth

• Smaller relative brain size

• No true flight, no fossorial herbivores, large marsupial carnivores are extinct

Marsupial reproduction

• Bifurcated reproductive tract (female) and bifurcated penis (male)

• Choriovitilline placenta

• Limited intrauterine development time and accelerated development of muscular forelimb

– Precludes forelimb from becoming hooves, flippers, or wings

Marsupial reproduction con’t

• Paired sperm in New World marsupials

• Marsupium - open anteriorly or posteriorly, folds of skin

– Best developed in arboreal species, and species that burrow or jump

• Neonate (no more than 1 g) climb to a teat

– Once attached, teat swells, keeping neonate in place

Zoogeography

• Living marsupials occur in NA, Central and SA, Australasia

• Marsupials are thought to have originated in North America

– Oldest fossils dating 100 mya

• Panamanian land bridge developed 2 to 5 mya, major interchange of fauna

• 65 mya, marsupials moved from SA through Drake Passage to Antartica and Australasia

• Australian marsupials evolved in relative isolation from eutherians

Orders and Families

• 7 orders and 18 extant families

• Polyprotodonts - unshortened mandible, lower incisors small and unspecialized

• Diprotodont - shortened mandible with first pair of lower incisors enlarged to meet upper incisors

• Didactylous - unfused toes, each in own skin sheath

• Syndactylous - skeletal elements of 2nd and 3rd toes in common skin sheath

Dentition

Digits

Didelphimorphia die-delf-uh-MOR-fee-uh

• Single family, Didelphidae

• New World distribution

• Terrestrial burrowers, semiarboreal

• Solitary and opportunistic feeders

• Most specialized didelphid, water opossum (aquatic, webbed hind feet, marsupium watertight during dives)

Didelphimorphia morphology

• Paired spermatozoa

• Pentadactyly, with primitive metatherian dental formula 5/4, 1/1, 3/3, 4/4 =50

• Polyprotodont and didactylous

• Have sparsely haired prehensile tails and opposable pollex (thumb on forefoot)

• Some have incrassated tail (store fat in the base)

Paucituberculata paw-see-too-ber-KYOO-lah-tuh

• Single family, Caenolestidae kee-noh-LESS-tuh-dee

• “Shrew” or “rat” opossum

• Dense vegetation of northwestern S. America

• Nocturnal, insectivorous or omnivorous, and terrestrial

• Paired spermatozoa

Paucituberculata morphology

• Small, shrewlike

• Long rostrum, adult weigh 40g

• No marsupium

• Didactylous, only New World marsupial that is diprotodont

• Lower canine vestigial

Microbiotheria my-crow-bio-THER-ee-uh

• Single family, Microbiotheriidae

• One species, monito del monte (Dromiciops gliroides)

• South central Chile in beech/bamboo forest

• Small, 16-30g

• Have prehensile tail and pouch

• Greatly inflated auditory bullar

• Called “colocolos” by natives, bad omen

Dasyuromorphia (das-ih-yoor-oh-MOR-fee-uh)

• Small to medium sized, incl. carnivorous species (Tasmanian devil and quoll)

• Polyprotodont and didactylous

• Canines well-developed, have carnassial dentition

• Tails never prehensile

• 3 families: Thylacinidae, Myrmecobiidae, Dasyuridae

Numbat

Dasyuromorphia con’t

Peramelemorphia per-uh-mel-eh-MOR-fee-uh

• Bandicoots and bilbies - Australasia

• 2 families, Peramelidae and Peroryctidae

• Terrestrial omnivores

• Have chorioallantoic placenta (no villi)

• Short compact body with long pointed rostrum

• Bandicoots have well-developed patella (kneecap) and no clavicle

• Polyprotodont

• Marsupium opens posteriorly

Diprotodontia (dih-pro-toh-DON-she-uh)

• 8 families, 116 species

• Diprotodont, syndactylous

• In arboreal diprotodonts, first two digits of forefeet oppose the other three digits - schizodactylous

– Hallux (big toe) opposable (not in terrestrial species)

Phascolarctidae (fas-koh-LARK-tuh-dee)

• Koala

Vombatidae (vom-BAT-uh-dee )

• Wombat - powerful burrower 30 kg

• Grazing herbivore, dentition open-rooted

Phalangeridae (fah-lan-JER-uh-dee)

• Brushtail possum, cuscus

• Long prehensile tail, excellent climbers

Potoroidae (pot-uh-ROY-dee)

• Bettongs, potoroos

• Weak prehensile tail

• Upper canine well developed

• Have embryonic diapause

Macropodidae (ma-crow-POD-uh-dee )

• Kangaroos and wallabies

• Grazing herbivores

• Similar to artiodactyls

• Molar hypsodont*, mesial drift of cheekteeth

*high-crowned teeth and enamel which

extends past the gum line .

This provides lots of extra material for wear

Burramyidae (bur-ruh-MY-uh-dee )

• Pygmy possum - smallest possum

• 7-50g

• Exhibit embryonic diapause

Acrobatidae (ak-crow-BAH-tuh-dee )

• Feathertailed glider and feather-tailed possum

• New Guinea

• Stiff, featherlike hairs on side of tails

• Feathertailed glider - smallest gliding mammal (10-14g)

• Both species nectivorous with brush-tipped tongue

• Exhibit embryonic diapause

Pseudocheiridae (soo-doh-KY-ruh-dee)

• Slow-moving, ringtail possum

• Feed on leaves, aboreal

• Molars are selenodont (elongated)

• Schizodactylous digits

• Prehensile tail

• Have marsupium

Petauridae (pet-OR-uh-dee)

• Striped possums and wrist-winged gliders

• Petaurus similar to NA gliding squirrels

• Prehensile tail, opposable hallux

• Have marsupium

• Diprotodont but molars bunodont

Tarsipedidae
(tar-sih-PED-uh-dee)

• Honey possum

• 12 g

• Nectivorous

• Long pointed rostrum with brush-tipped tongue, small peglike teeth

• Prehensile tail, hallux opposable, pads on digits for gripping branches

• Delayed implantation

Notoryctemorphia (noh-toh-rik-teh-MOR-fee-uh )

• Marsupial mole

• Secretive, completely fossorial, eats beetles and larvar

• Similar to eutherian talpids and chrysochlorids

• “Swim” through ground, substrate collapse behind, no permanent tunnels

• Spend time aboveground too, active both day and night

• Fusiform, scooplike claw, thick keratinized nasal shield (pushing dirt)

• Cervical vertebrae fused, no pinna, vestigial eye

Notoryctemorphia con’t

• Epipubic bone reduced

• Molars zalambdodont (v-shaped)

• Eaten by aborigines

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

• The major eutherian orders

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

– 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

• 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

• The other group of anthropoids, the hominoids

– Consists of primates informally called apes

• Hominoids

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

• 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

• 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

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

• 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

• 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

Marine vertebrates

• Early Mesozoic had primitive bony fish

• Modern teleost fishes

– developed by late Jurassic

– highly mobile jaws and swim bladder

• Marine reptiles (not dinosaurs)

– plesiosaurs (long necked fish-catchers)

– icthyosaurs (fish-lizards, dolphin-like reptiles)

– mosasaurs (related to monitor lizards)

Marine vertebrates