Study traces AIDS virus origin to 100 years ago
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Study traces AIDS virus origin to 100 years ago.

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Study traces AIDS virus origin to 100 years ago

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Study traces AIDS virus origin to 100 years ago

“Researchers took advantage of the fact that HIV mutates rapidly. So two strains from a common ancestor quickly become less and less alike in their genetic material over time. That allows scientists to "run the clock backward" by calculating how long it would take for various strains to become as different as they are observed to be. That would indicate when they both sprang from their most recent common ancestor.

The new work used genetic data from the two old HIV samples plus more than 100 modern samples to create a family tree going back to these samples' last common ancestor. Researchers got various answers under various approaches for when that ancestor virus appeared, but the 1884-to-1924 bracket is probably the most reliable, Worobey said.”


cynodonts


cynodonts

Mammaliamorpha

Mammaliaformes

Mammalia: All descendants from

the MRCA of living mammals.


cynodonts

Mammaliamorpha

Mammaliaformes


cynodonts

Mammaliamorpha (transition to

dentary-squamosal joint begins)

Mammaliaformes

(formation of dentary-squamosal

“single jaw hinge” complete)


TraitPelycosaursTherapsidsCynodonts

Posture:sprawlingintermediateupright

Teeth:weakly heterodontincreasingly heterodontstrongly hetero

Palate:no secondary palatepartialcomplete

“-apsidy”small temporal fenestraenlarged fenestravastly expanded

Postdentary bones:present, largepresent, reducedabsent

greatly reduced


cynodonts

Mammaliamorpha (transition to

dentary-squamosal joint begins)

Mammaliaformes

(formation of dentary-squamosal

“single jaw hinge” complete)

Mammalia: All descendants from

the MRCA of living mammals.


Mammalia

Mammaliaformes

Mammaliamorpha


Mesozoic

Morganucodon

Paleozoic

Mammalia (and some mammaliaforms)

  • Completion of dentary-squamosal jaw joint

  • Cheekteeth divided into premolars and molars

  • Diphyodonty

  • BUT TINY! For 170 million years!


cynodonts

Mammaliamorpha

Mammaliaformes

Mammalia: All descendants from

the MRCA of living mammals.


Mammalia

Mammaliaformes

Mammaliamorpha


Multituberculates

(extinct prototherians)


Multituberculates

(extinct prototherians)

Late Jurassic-Mid. Miocene

(ca. 150 m.y.)


Multituberculates

(extinct prototherians)

Late Jurassic-Mid. Miocene

(ca. 150 m.y.)

Diverse, found on all continents


Multituberculates

(extinct prototherians)

Late Jurassic-Mid. Miocene

(ca. 150 m.y.)

Diverse, found on all continents

Ever-growing lower incisors,

plagialacoid (blade-like)

molariform teeth


Multituberculates

(extinct prototherians)

Late Jurassic-Mid. Miocene

(ca. 150 m.y.)

Diverse, found on all continents

Ever-growing lower incisors,

plagialacoid (blade-like)

molariform teeth

Outcompeted to extinction?

(rodents, early primates...)


(INFRACLASSES)

Prototheria (SUBCLASS)

Metatheria

Eutheria

Theria

(SUBCLASS)

Mammalia (CLASS)

Mammaliaformes

Mammaliamorpha


Extant mammalian diversity

Class MAMMALIA

Subclass Prototheria

Subclass Theria

Infraclass Metatheria

1 Order (Monotremata)

2 Families

3 species

7 Orders

19 Families

272 species

Infraclass Eutheria

18 Orders

114 Families

4354 species


Extant mammalian diversity

Class MAMMALIA

Subclass Prototheria

Subclass Theria

Infraclass Metatheria

1 Order (Monotremata)

2 Families

3 5 species

7 Orders

19 21 Families

272 331 species

xx

x

xxx

Infraclass Eutheria

xx

18 21 Orders

114 130 Families

4354 5078 species

xxx

xxxx


The radiation of placental mammals

Since end of Mesozoic, placental (eutherian) mammals dominant terrestrial vertebrates on all continents except Australia and Antarctica.

When and why did this diversification occur?


“Age of Mammals”

K/T boundary

“Age of Dinosaurs”


Tertiary


K/T

boundary


Most/all eutherian orders originated & diversify

AFTER K/T

(traditionally, fossils supported this)


Most/all eutherian orders originated & diversify

AFTER K/T

(traditionally, fossils supported this)

Orders originate BEFORE K/T but don’t diversify until

AFTER K/T

(more recently discovered fossils support)


Most/all eutherian orders originated & diversify

AFTER K/T

(traditionally, fossils supported this)

Orders originate BEFORE K/T but don’t diversify until

AFTER K/T

(more recently discovered fossils support)

Most orders originate & diversify BEFORE K/T

(older molecular studies support)


Subclass Prototheria

1 Order (Monotremata)

2 Families

Tachyglossidae (echidnas or “spiny anteaters”)

4 species.

Ornithorhynchidae (platypus)

1 species


Subclass Prototheria

Few fossils, never very diverse. BUT PERSISTED.


Subclass Prototheria

Few fossils, never very diverse. BUT PERSISTED.

Echidnas: fossils from 55-60 Mya, oldest in S. AMERICA


Subclass Prototheria

Few fossils, never very diverse. BUT PERSISTED.

Echidnas: fossils from 55-60 Mya, oldest in S. AMERICA

Platypus: fossils from 120 Mya, oldest in AUSTRALIA

(Paleocene fossils in S. AMERICA).


Subclass Prototheria

Few fossils, never very diverse. BUT PERSISTED.

Echidnas: fossils from 55-60 Mya, oldest in S. AMERICA

Platypus: fossils from 120 Mya, oldest in AUSTRALIA

(Paleocene fossils in S. AMERICA).

Many plesiomorphic features, but some apomorphies.


Subclass Prototheria

SKULL FEATURES:

•No teeth in living adults BUT fossil platys & living

neonates have, then lose. LOSS=apomorphy


Subclass Prototheria

SKULL FEATURES:

•No teeth in living adults BUT fossil platys & living

neonates have, then lose. LOSS=apomorphy

•No lacrimals (APOMORPHY)


Subclass Prototheria

SKULL FEATURES:

•No teeth in living adults BUT fossil platys & living

neonates have, then lose. LOSS=apomorphy

•No lacrimals (APOMORPHY)


Subclass Prototheria

SKULL FEATURES:

•No teeth in living adults BUT fossil platys & living

neonates have, then lose. LOSS=apomorphy

•No lacrimals (APOMORPHY)

•Cranial sutures fused, indistinct (APOMORPHY)


Subclass Prototheria

SKULL FEATURES:

•No teeth in living adults BUT fossil platys & living

neonates have, then lose. LOSS=apomorphy

•No lacrimals (APOMORPHY)

•Cranial sutures fused, indistinct (APOMORPHY)

•Jugal reduced or absent (APOMORPHY)


Subclass Prototheria

SKELETAL FEATURES:


Subclass Prototheria

SKELETAL FEATURES:

•Epipubic bones present, large (PLESIOMORPHY)


Subclass Prototheria

SKELETAL FEATURES:

•Epipubic bones present, large (PLESIOMORPHY)

•Cervical ribs (PLESIOMORPHY)


Subclass Prototheria

SKELETAL FEATURES:

•Epipubic bones present, large (PLESIOMORPHY)

•Cervical ribs (PLESIOMORPHY)

•Horny, hollow spur on inside of ankle (APOMORPHY)


Warren et al. (2008). Nature 453, 175-183.


Subclass Prototheria

SKELETAL FEATURES:

•Epipubic bones present, large (PLESIOMORPHY)

•Cervical ribs (PLESIOMORPHY)

•Horny, hollow spur on inside of ankle (APOMORPHY)

•Pectoral girdle with large precoracoids, coracoids,

interclavicle (PLESIOMORPHY)


Subclass Prototheria

SKELETAL FEATURES:

•Epipubic bones present, large (PLESIOMORPHY)

•Cervical ribs (PLESIOMORPHY)

•Horny, hollow spur on inside of ankle (APOMORPHY)

•Pectoral girdle with large precoracoids, coracoids,

interclavicle (PLESIOMORPHY)

•Skeleton sprawling, “reptilian” (PLESIOMORPHY)

BUT, good for swimming, digging.


Subclass Prototheria

OTHER FEATURES:

•Pouch (echidnas only)


Subclass Prototheria

OTHER FEATURES:

•Pouch (echidnas only)

•Testes permanently abdominal (no scrotum)


Subclass Prototheria

OTHER FEATURES:

•Pouch (echidnas only)

•Testes permanently abdominal (no scrotum)

•Uteri fused


Subclass Prototheria

OTHER FEATURES:

•Pouch (echidnas only)

•Testes permanently abdominal (no scrotum)

•Uteri fused

•Leathery egg with nutrient-rich yolk


Subclass Prototheria

OTHER FEATURES:

•Pouch (echidnas only)

•Testes permanently abdominal (no scrotum)

•Uteri fused

•Leathery egg with nutrient-rich yolk

•Rostrum lacks vibrissae, elongate

•cloaca (but....)


Subclass Prototheria

OTHER FEATURES:

•Pouch (echidnas only)

•Testes permanently abdominal (no scrotum)

•Uteri fused

•Leathery egg with nutrient-rich yolk

•Rostrum lacks vibrissae, elongate

•cloaca (but...)

•Endothermic, but low Tb and metabolic rates


Subclass Prototheria

OTHER FEATURES:

•Pouch (echidnas only)

•Testes permanently abdominal (no scrotum)

•Uteri fused

•Leathery egg with nutrient-rich yolk

•Rostrum lacks vibrissae, elongate

•cloaca (but...)

•Endothermic, but low Tb and metabolic rates

•Electroreception (snout), including echidnas


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