trait pelycosaurs therapsids cynodonts posture:sprawlingintermediateupright
DESCRIPTION
Trait Pelycosaurs Therapsids Cynodonts Posture:sprawlingintermediateupright Teeth:weakly heterodontincreasingly heterodontstrongly hetero Palate:no secondary palatepartialcomplete “-apsidy”small temporal fenestraenlarged fenestravastly expanded - PowerPoint PPT PresentationTRANSCRIPT
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Trait Pelycosaurs Therapsids CynodontsPosture: sprawling intermediateupright
Teeth: weakly heterodont increasingly heterodontstrongly hetero
Palate: no secondary palate partialcomplete
“-apsidy” small temporal fenestra enlarged fenestravastly expanded
Postdentary bones: present, large present, reducedabsent
greatly reduced
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Mammaliaformes (formation of dentary-squamosal“single jaw hinge” complete)
Mammalia: All descendants fromthe MRCA of living mammals.
cynodonts
Mammaliamorpha (transition todentary-squamosal joint begins)
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MammaliamorphaMammaliaformes
Mammalia
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Morganucodon
•Completion of dentary-squamosal jaw joint•Cheekteeth divided into premolars and molars•Diphyodonty
•BUT TINY! For 170 million years!
Pal
eozo
icM
esoz
oic
Mammalia (and some mammaliaforms)
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Mammaliamorpha
Mammaliaformes
Mammalia: All descendants fromthe MRCA of living mammals.
cynodonts
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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...)
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MammaliamorphaMammaliaformes
Mammalia (CLASS)
Met
athe
riaM
etat
heria
Euth
eria
Euth
eria
Theria(SUBCLASS)
ProtoPrototheria (SUBCLASS)theria (SUBCLASS)
(INFRACLASSES)(INFRACLASSES)
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Extant mammalian diversity
1 Order (Monotremata)2 Families3 5 species
Infraclass Metatheria
Infraclass Eutheria
7 Orders19 21 Families272 331 species
18 21 Orders114 130 Families4354 5078 species
Subclass Prototheria Subclass Theria
Class MAMMALIA
x xxxxx
xxxxx
xxxx
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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?
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“Age of Mammals”
“Age of Dinosaurs”
K/T boundaryK/T boundary
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K/TK/Tboundaryboundary
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Most/all eutherian orders originated & diversifyAFTER K/T
(traditionally, fossils supported this)
Orders originate BEFORE K/T but don’t diversify untilAFTER K/T
(more recently discovered fossils support)
Most orders originate & diversify BEFORE K/T(older molecular studies support)
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1 Order (Monotremata) 2 Families
Tachyglossidae (echidnas or “spiny anteaters”)4 species.
Ornithorhynchidae (platypus)1 species
Subclass Prototheria
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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
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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
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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
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Warren et al. (2008). Nature 453, 175-183.
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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
Subclass Prototheria