Homework to be emailed to valenciabiologyhw@gmail.com

    1. Desribe the 4 unique characteristics of chordates
    2. Compare and contrast members of Agnatha, Placadermi, and Chondrichthyes
    3. Summarize the evidence supporting the fact that amphibians evolved from crossopterygians
    4. List the distinguishing characteristics of members of the class Aves and explain any special adaptations for flight
    5. Compare and contrast the four main evolutionary lines of placental mammals
    6. 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

      question #1

      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 _____.

       

•       Vertebrate Lecture Notes--animals 3 A and 3 B

• 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
 
• -One hypothesis for the origin of “fish-like” chordates is paedomorphosis of the tadpole larva.
• -This seems to have happened once in the origin of “larvaceans,” which are small, planktonic urochordates that retain the postanal tail, etc., throughout their lives.
• -This may have happened at least one other time, giving rise to the rest of the chordates.
 
• The Chordates have four distinguishing characteristics:
• - Pharyngial gill slits
• - Muscular postanal tail (for locomotion)
• - Notochord (which keeps the body from telescoping)
• - A dorsal, hollow nerve tube (which coordinates movement)
• Note that 3 of these are associated with locomotion
 
 
• -Phylogeny of Chordates
• - The chordates as a group are pretty diverse in form, too, containing some members that are decidedly un-vertebate like.
 
• -The Urochordata appear to be the sister group to the lineage that contains the vertebrates
 
Urochordates are sedentary or slow-moving animals
• Tunicates (sea squirts) are attached to the bottom as adults – and use a huge pharyngial basket (with gill slits) to filter the water – much like a clam.
 
• Salps are free-floating filter feeders, also using their pharynx and gill slits
• So… where’s the tail?
 
 
• -The other three chordate characteristics are found in the larval stage – the “tadpole larva.” It is the dispersal stage for tunicates, which cannot move as adults. As the dispersal stage, the tadpole larva has the postanal tail, notochord, and dorsal nerve tube.
• - But even so, where did fish come from?
 
 
• -One hypothesis for the origin of the rest of the chordates from a urochordate-like ancestor: paedomorphosis (also known as paedogenesis)
• -Paedomorphosis is a phenomenon in which sexual maturity is achieved in the larval or juvenile body form. Either maturation is accelerated, or body development is prolonged (maybe forever).
• -Evolutionary changes in relative rates of development are common. The Mexican axlotl is a paedomorphic salamander that keeps its gills and swimming tail throughout its life.
 
 
 
 
 
 
• The animals called vertebrates
– Get their name from vertebrae, the series of bones that make up the backbone
 
 
• There are approximately 52,000 species of vertebrates
– Which include the largest organisms ever to live on the Earth
 
• 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
 
Derived Characters of Chordates
• All chordates share a set of derived characters
– Although some species possess some of these traits only during embryonic development
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
Notochord
• 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
 
• Tunicates most resemble chordates during their larval stage
– Which may be as brief as a few minutes
 
• As an adult
– A tunicate draws in water through an incurrent siphon, filtering food particles
Early Chordate Evolution
• The current life history of tunicates
– Probably does not reflect that of the ancestral chordate
Lancelets
• Lancelets, subphylum Cephalochordata
– Are named for their bladelike shape
 
• Lancelets are marine suspension feeders
– That retain the characteristics of the chordate body plan as adults
 
• Gene expression in lancelets
– Holds clues to the evolution of the vertebrate form
 
• 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
 
• Neural crest cells
– Give rise to a variety of structures, including some of the bones and cartilage of the skull
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
 
• In other Cambrian rocks
– Paleontologists have found fossils of even more advanced chordates, such as Haikouichthys
Hagfishes
• The least derived craniate lineage that still survives
– Is class Myxini, the hagfishes
 
 
• Hagfishes are jawless marine craniates
– That have a cartilaginous skull and axial rod of cartilage derived from the notochord
– That lack vertebrae
 
• 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
 
 
 
 
Fossils of Early Vertebrates
• Conodonts were the first vertebrates
– With mineralized skeletal elements in their mouth and pharynx
 
• Armored, jawless vertebrates called ostracoderms
– Had defensive plates of bone on their skin
Origins of Bone and Teeth
• Mineralization
– Appears to have originated with vertebrate mouthparts
• The vertebrate endoskeleton
– Became fully mineralized much later
 
• 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
 
• A. Vertebrate jaws evolved from skeletal supports of pharyngeal slits
 
• 1. Animals that replaced jawless vertebrates, and are Gnathostomes.
•
• 2. Members of group have two pairs of fins.
•  
 
 
• 3. Jaws and fins allowed fish to become active in pursuit of food and in biting off chunks of flesh.
 
• 4. Jaws evolved from modifications of skeletal elements of anterior pharyngeal gill slits.
 
 
 
• 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
 
• Another group of jawed vertebrates called acanthodians
– Radiated during the Devonian period
– Were closely related to the ancestors of osteichthyans
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
 
 
• Most sharks
– Have a streamlined body and are swift swimmers
– Have acute senses
 
• A second subclass
– Is composed of a few dozen species of ratfishes
 
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
 
Ray-Finned Fishes
• Class Actinopterygii, [Ac-tin-o-ter-y-gi-i ] the ray-finned fishes
– Includes nearly all the familiar aquatic osteichthyans
 
 
• 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
 
 
• 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
 
• Extraordinary fossil discoveries over the past 20 years
– Have allowed paleontologists to reconstruct the origin of tetrapods
 
 
 
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
 
• Order Anura
– Includes frogs and toads, which lack tails
 
• Order Apoda
– Includes caecilians, which are legless and resemble worms
 
• Amphibian means “two lives”
– A reference to the metamorphosis of an aquatic larva into a terrestrial adult
 
 
• Amphibians represent the first truly tetrapod vertebrates
– first to move about and support themselves on land
• All amphibians have bony skeletons
• Most have 4 limbs, except Caecilians (limbless) and Sirens (forelimbs only)
• Many have webbed feet
• Typically the glandular skin is smooth, moist, and lacks scales
 
– Caecilians have concealed dermal scales
• One advance associated with a more terrestrial existence is the refinement of the ear
– the amphibian ear, unlike that of fishes, consists of three components
• Inner ear, middle ear, outer ear
• There is increased sensitivity to accommodate airborne sounds
 
 
• Gas exchange occurs through lungs, gills, and/or the skin
– Some salamanders have no lungs (secondarily lost)
• Adults have double circulation
– Both a pulmonary and a systemic circuit
• Heart has three chambers
– Two atria and one ventricle
– Some mixing of oxygenated and deoxygenated blood occurs in ventricle
 
 
 
• The evolution of the tetrapod limb was the third major hallmark in vertebrate evolution
• In early forms, these limbs represented modified Sarcopterygian pectoral and pelvic fins
 
 
• Development of limbs required only a few minor modifications
– elongation of proximal elements into long-bones of limbs
– Proliferation of more distal elements into bones of feet
– Elaboration of pectoral and pelvic girdles (for anchoring the limbs)
• Early locomotion was probably very crude
– Orientation of limb did not effectively allow body to be raised above substrate
– Limbs acted as pivot points rather than for propulsion. Modern salamanders still move about in this way.
 
 
• Emergence on to land required adaptations to accommodate desiccation
– amphibians have an external layer of skin, the stratum corneum, that consists of a single layer of dead cornified cells
• Reduces water loss through skin to some extent
 
 
• However, amphibian eggs are very vulnerable to desiccation
– Hence, amphibians are reproductively constrained to exist in moist environments.
 
• Fertilization is external in anuran and some urodelids
– most salamanders have external fertilization, but no copulation
– Males deposit a spermatophore which is picked up by the female and placed into a spermatheca (in wall of cloaca)
• Eggs are fertilized as they pass through the cloaca
 
 
• Most amphibians are oviparous
– -females lay eggs
• Some amphibians undergo direct development in the egg
– -embryos pass through larval stage in the egg and emerge from the egg as miniature versions of the adults.
• In most amphibians, the young must pass through a larval stage
– larvae are aquatic with external gills
 
• In a few forms, the adults will retain larval characteristics
– = neoteny
• A very few forms are viviparous
– the females retain the eggs in their bodies until they are ready to hatch.
 
 
• It is clear that amphibians evolved from some lineage of Sarcopterygian fishes
– -However the details of this origin remain obscure
• One fossil group, from the Crossopterygian lineage, that provides a good candidate for amphibian origins are the Rhipidistians [rı˘’pı˘-dı˘s’te―-nz]
– shared many characteristics with fossil amphibians
• Limb/fin structure, jaw structure, both had labyrinthodont teeth
 
 
 
– the arrangement of skull bones is similar
– the amphibian limb can be derived from the fin structure
– the rhipidistians lived in shallow freshwater lakes and almost certainly had lungs and breathed air
– both rhipidistians and early amphibians have a similar structure to their teeth - called a labyrinthodont pattern from the complex folding of the walls of the pulp cavity
– rhipidistians were the only fish which had developed an opening to the nostrils inside the mouth - a feature which is found in all the land vertebrates.
 
 
• However, recent mitDNA evidence shows that modern amphibians are more similar to lungfishes (Dipnoi) than to Coelacanths (Crossopterygii)
– this suggests a different origin for the amphibians
– Critics reject this argument based on certain methodological arguments
 
 
 
• Though actual origins are uncertain, it is clear that there was plenty of selective pressure for amphibians to emerge onto land
– the Devonian was a period of tremendous climatic fluctuation
• Wet and dry spells – dry spells would have set up intense competition in aquatic habitats, would favor an ability to move from one pond to another, oxygen poor waters would favor air-breathing
 
 
– Also, at this time, there was a tremendous radiation of arthropods into the terrestrial environment
• Centipedes, millipedes, spiders, insects, etc.
• This would create an open niche in a relatively low-competition terrestrial environment
– Lastly, the ability to temporarily move out of water would allow early amphibians a means of escaping from aquatic predators.
 
 
 
• The fossil record of amphibians includes two extinct subclasses
– Labyrinthodontia and Lepospondyli
• The earliest fossil amphibians belonged to the Labyrinthodontia
 
 
 
• Labyrinthodonts first appeared in the upper Devonian
– were the most abundant and diverse amphibians though the Carboniferous, Permian, and Triassic
– Some were quite large, reaching a length of 5 feet.
– Most were aquatic or primarily aquatic
– Many retained fish-like tails, some retained internal gills
 
 
 
• Several groups of Labyrinthodonts existed, two were important for vertebrate evolution
– Anthracosaurs represented a small group but are important because they are believed to be ancestral to reptiles
– Temnospodylians were common during Permian and are suggested to be ancestral to modern Amphibians
 
origins
• The other fossil subclass was Lepospondyli
– represent a group of small, salamander-like amphibians that appeared in the Carboniferous and Permian.
– Though superficially similar to salamanders, they are not believed to be closely related to any living amphibians
• Based on unique structure of the vertebrae
 
Living Amphibians
• Modern amphibians all belong to the Subclass Lissamphibia
– First appeared in Triassic about 200 mya
• First true frog – Jurassic (190 mya)
• First salamander – Jurassic (145 mya)
• First Caecilians – Jurassic (195 mya)
 
 
 
• Because many forms have delicate skeletons, they don’t preserve well.
– Thus the fossil record is rather poor
– As a result the evolutionary relationships among living taxa are poorly understood
 
 
 
• 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
 
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
• Allantois. (a˘-la˘n’to―-ı˘s )) The allantois is a disposal sac for certain metabolic wastes produced by the embryo. The membrane of the allantois also functions with the chorion as a respiratory organ
Chorion. [kτ’re―-o˘n]  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.
Amnion. The amnion protects the embryo in a fluid-filled cavity that cushions against mechanical shock.
 
 
 
• 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 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?
• -It’s 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 aren’t 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 don’t 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˘p’sı˘d] were diversifying
• The diapsids are composed of two main lineages
– The lepidosaurs [le˘p’ı˘-do―-sτrz] and the archosaurs[δr‘ko―-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 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―-thξr’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
 
 
 
Numbat
Dasyuromorphia con’t
 
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 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
 
 
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―-thξr’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