Fishes that have swim bladders can regulate their density and, thus, their buoyancy. There are two types of swim bladder: physostomus and physoclistus. The ancestral version is the physostomus version, in which the swim bladder is connected to the esophagus via a short tube (Figure 34.1). The fish fills this version by swimming to the surface, taking gulps of air, and directing them into the swim bladder. Air is removed from this version by "belching." The physoclistus version is more derived, and has lost its connection to the esophagus. Instead, gas enters and leaves the swim bladder via special circulatory mechanisms within the wall of the swim bladder.
Rank the following fish, from most to least, in terms of the amount of energy it must use to maintain its position (depth) in the water column over the long term.
1. physoclistus fish
2. physostomus fish
3. chondrichthyan fish
7. If a physoclistus fish removes gas from its swim bladder, this fish's density cannot actually change until that gas arrives at the _______________
8. Which shark structure is most analogous to a swim bladder full of gas?
9. When a shark stops swimming, it does which of the following?
1. sinks
2. quickly dies
3. oxygenates its blood less effectively
10.This phylogenetic tree indicates that birds are most closely related to _____.
11. This phylogenetic tree indicates that the most recent common ancestors of reptiles, birds, and mammals are _____.
Other nutrients are stored in the albumen 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
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
Temperature Relationships in Animals -Why are temperature relationships
important for land animals?
-Its hard to get moving when it is cold
-Few reptiles live at high altitudes and high latitudes, and if they do, they
often undergo hibernation during winter.
-But do lizards really fit all of the cold-blooded stereotypes?
-Lizards arent always cold blooded. They can maintain relatively high body
temperatures even higher than some birds an mammals and body temperature can
exceed air temperature
Body Temperature Cold-blooded
Body temperature = environmental temp.
Warm blooded
Body temperature usually > environmental temp.
But the source of body heat does differ between lizards and birds or mammals.
They dont generate their own heat, but instead take up heat from the sun, or
from rocks.
Source of Body Heat
Ectotherm
Body temperature depends on environment
Endotherm
Body temperature depends on internal source of heat
-Lizards and other living reptiles can regulate their body temperature
behaviorally, by exposing themselves to the sun, or to warm surfaces. They are
truly ectothermic, but are still capable of maintaining constant, high body
temperatures,
under a certain range of
conditions.
Temperature Relationships in Animals: Summary
-Most fish:
Cold-blooded, poikilothermic, ectotherms
-Lizards & Snakes:
Warm-blooded (often), homeothermic (often), ectotherms (typically)
-Birds & Mammals:
Warm-blooded, homeothermic, endotherms helps to permit an active lifestyle
in a range of environmental conditions, but at an energetic cost.
-Dinosaurs?
Modeled after lizards and other ecothermic reptiles?
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 [dı―-a˘psı˘d] were diversifying
The diapsids are composed of two main lineages
The lepidosaurs [le˘pı˘-do―-sτrz] and the archosaurs[δrko―-sτrz]
The dinosaurs
Diversified into a vast range of shapes and sizes
Included the long-necked giants called the theropods
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
Early Dinosaurs
Archosaurs replaced synapsid/reptile groups
Two major groups of reptiles
modern lizards and snakes
archosaurs
crocodiles, birds, dinosaurs, flying reptiles, many archic reptiles
archosaur radiation produced many unusual beasts
first true dinosaurs
small (< 1m) bipedal
hind limbs upright
Dinosaur groups
Two major groups based on pelvis shape
Saurischian (lizard-hipped)
sauropods (brontosaurus, etc.)
theropods (two-legged carnivores)
birds eventually developed from this line
Ornithiscian (bird-hipped)
all herbivorous
Anklyosaurs
Stegosaurs
Hadrosaurs, Pachycephalosaurs
Iguanodonts
Ceratopsids
The K-T extinctions
Extinctions were severe
Evidence is different for different groups
Dinosaurs, pterosaurs, many plants went extinct
Severe extinctions of coccolithoids and forams, brachiopods and ammonites
Microfossils tended to phase out slowly however, beginning millions of years
before the boundary
Tropical groups suffered most
Ammonites declining long before the boundary
Mammals cross nearly unscathed, but shift to placentals
Bulk of evidence indicates gradual decline over K
Impact hypothesis
Giant meteor impact
first suspected from Gubbio, Italy iridium layer
iridium rare element on earth, more abundant in meteors
iridium layer found all over the world now
shocked quartz another impact indicator?
Chixalub crater in the Yucatan, Mexico
suspected of being THE K-T impact
Mechanism for extinctions
dust hung in atmosphere and blocked sunlight, initiated global cooling
plants would die, triggering food chain collapse
total event may have lasted less than 50 years
Volcanic hypothesis
Gradual extinction record a problem for impact
Massive volcanic eruptions suggested
Deccan traps of India and flood basalts in Brazil
dated to last 500,000 yrs before KT boundary
would pump lots of ash and sulfuric acid into atmosphere
iridium also enriched in mantle rocks and volcanics
And the jury says...
Arguments are still going on
gradual extinctions seem to fit volcanic hypothesis
but complexities abound
neither model seems to completely account for all evidence
both events might have contributed to the declines
Lepidosaurs
One surviving lineage of lepidosaurs
Is represented by two species of lizard-like reptiles called tuatara
The other major living lineage of lepidosaurs
Are the squamates, [skwa―ma―tz] the lizards and snakes
Lizards
Are the most numerous and diverse reptiles, apart from birds
Snakes are legless lepidosaurs
That evolved from lizards
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
Alligators and Crocodiles
Crocodilians
Belong to an archosaur lineage that dates back to the late Triassic
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 birds 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 mothers 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―-thξre―-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 cont
Eggs are small, incubated for 10 to 11 days
Neonates have well developed forelimbs and shoulders
Monotremata cont
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 cont
Has small eyes and ears
Pentadactyle (five-toed) and manus (forefoot) is webbed
Long claws for digging burrow
Ornithorhynchidae cont
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 cont
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 cont
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 mothers body mass
Eutherians: litters weigh 50% of mothers 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 mothers 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 cont
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 cont
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
Numbat
Dasyuromorphia cont
Phascolarctidae (fas-koh-LARK-tuh-dee)
Koala
Vombatidae (vom-BAT-uh-dee )
Wombat - powerful burrower 30 kg
Grazing herbivore, dentition open-rooted
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
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
VI. Primates and the evolution of Homo sapiens
A. Primate evolution provides context for understanding human origins
1. Hands and feet adapted for grasping. Possess opposable thumb.
2. Large brains allow complex social behavior.
Figure 34.35 (p. 708) A phylogenetic tree of primates.
B. Hominid lineage diverged from other primates about 7 million years ago.
Humans compared to other hominids:
a. Brain size large size allows development of language and social behavior.
b. Jaw shape shortened to give a flatter face.
c. Bipedalism = walking on two legs.
- Frees hands to do other things.
- Eyes set higher; can see farther
Hominoids
Diverged from Old World monkeys about 2025 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 67 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 usecut 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
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 birds 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 mothers 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―-thξre―-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 cont
Eggs are small, incubated for 10 to 11 days
Neonates have well developed forelimbs and shoulders
Monotremata cont
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 cont
Has small eyes and ears
Pentadactyle (five-toed) and manus (forefoot) is webbed
Long claws for digging burrow
Ornithorhynchidae cont
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 cont
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 cont
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 mothers body mass
Eutherians: litters weigh 50% of mothers 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 mothers 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 cont
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 cont
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 cont
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 cont
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 2025 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 67 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 usecut 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