1. Trait Pelycosaurs Therapsids Cynodonts
Posture: sprawling intermediate upright
Teeth: weakly heterodont increasingly heterodont strongly hetero
Palate: no secondary palate partial complete
“-apsidy” small temporal fenestra enlarged fenestra vastly expanded
Postdentary bones: present, large present, reduced absent
greatly reduced
THIS IS WRONG! SEE LUO ET AL SCIENCE PAPER. THE REDUCTION BEGAN IN CYNODONTS BUT WASN’T COMPLETE UNTIL HADROCODIUM.

2. Mammaliamorpha (transition to
cynodonts
Mammaliamorpha (transition to
dentary-squamosal joint begins)
Mammaliaformes
(formation of dentary-squamosal
“single jaw hinge” complete)
Luo et al
Mammalia: All descendants from
the MRCA of living mammals.

3. Mammalia
Mammaliaformes
Mammaliamorpha

4. Completion of dentary-squamosal jaw joint
Mammalia (and some mammaliaforms)
Completion of dentary-squamosal jaw joint
Cheekteeth divided into premolars and molars
Diphyodonty
BUT TINY! For 170 million years!
Paleozoic
Mesozoic
Morganucodon
THESE ARE FOSSILIZABLE CHARACTERS USED TO DIAGNOSE FOSSIL TAXA.

5. Mammalia: All descendants from the MRCA of living mammals.
cynodonts
Mammaliamorpha
Mammaliaformes
Luo et al
Mammalia: All descendants from
the MRCA of living mammals.

6. 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...)

7. Theria (SUBCLASS) Mammalia (CLASS) Mammaliaformes Mammaliamorpha
(INFRACLASSES)
Prototheria (SUBCLASS)
Metatheria
Eutheria
Theria
(SUBCLASS)
Mammalia (CLASS)
Mammaliaformes
Mammaliamorpha

8. Warren et al. 2008

9. Extant mammalian diversity
Class MAMMALIA
Subclass Prototheria
Subclass Theria
Infraclass Metatheria
1 Order (Monotremata)
2 Families
3 5 species
7 Orders
19 21 Families
species xx x
xxx
Infraclass Eutheria xx
18 21 Orders
Families
species
xxx
xxxx

10. 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?

11. “Age of Mammals” K/T boundary “Age of Dinosaurs”
Why “K”? For Kreide, the German translation for Cretaceous.

12. BUT, this has increasingly been challenged, mainly by molecular clock studies but also by some fossils that push the origins of many of these orders back.
K/T
boundary

13. Most/all eutherian orders originated & diversify
AFTER K/T
(traditionally, fossils supported this)
Orders originate BEFORE K/T but don’t diversify until
(more recently discovered fossils support)
Most orders originate & diversify BEFORE K/T
(older molecular studies support)

14. Springer et al. 2003ish. Majority of recent studies support the long fuse. Bininda-Emmonds supertree paper argues that all modern orders diverged by 75 Mya but

15. Bininda-Emmonds supertree paper argues that all modern orders diverged by 75 Mya butradiations of modern families not till after K/T.

16. Subclass Prototheria
1 Order (Monotremata)
2 Families
Tachyglossidae (echidnas or “spiny anteaters”)
4 species.
Ornithorhynchidae (platypus)
1 species

17. Subclass Prototheria
Few fossils, never very diverse. BUT PERSISTED.
Echidnas: fossils from Mya, oldest in S. AMERICA
Platypus: fossils from 120 Mya, oldest in AUSTRALIA
(Paleocene fossils in S. AMERICA).
Many plesiomorphic features, but some apomorphies.

18. 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)

19. 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.

20. The epipubic bone acts as a lever that is retracted (depressed) to stiffen the trunk between the diagonal limbs that support the body during each step. This cross-couplet kinetic linkage and the stiffening function of the epipubic bone appear to be the primitive conditions for mammals.
THEY HELP STIFFEN/STRENGTHEN THE TRUNK THE TRUNK.

21. TWO ECHIDNAS (LEFT), PLATYPUS (RIGHT)

23. Platypus venom: coctail of at least 19 different substances
Platypus venom: coctail of at least 19 different substances. Several of these mapped onto tree show that ‘local’ duplications of genes with very different functions have occurred convenrgently.
whether or not venom unique to platypus or simply lost in echidnas still unknown. Echidnas have the spur in males.
Original caption: The diagram illustrates separate gene duplications in different parts of the phylogeny for platypus venom defensin-like peptides (vDLPs), for lizard venom crotamine-like peptides (vCLPs) and for snake venom crotamines. These venom proteins have thus been co-opted from pre-existing non-toxin homologues independently in platypus and in lizards and snakes
Warren et al. (2008). Nature 453,

24. All but scapula and clavicle lost in all other mammals.

25. 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