1. Mammal characteristics Soft anatomy Skin glands (sweat, scent, sebaceous) Lactation Hair Diaphragm 4-chambered heart High metabolic rate Hard anatomy (i.e., in fossil record) Three ear ossicles Single bone in mandible Complex teeth (heterodont & diphyodont)

2. TrirachodonCynognathus Therapsida – advanced cynodonts Probainognathus

4. Jaw evolution – pelycosaur to mammal

5. Secondary Palate

6. Procynosuchus Probainognathus Canis Primitive cynodont advanced cynodont modern mammal premaxilla maxilla palatine

7. PELVIS & HIND LIMB Posterior Lateral Pelycosaur Dimetrodon Therapsid Thrinaxodon

8. HEAD ARTICULATION occipital atlas - axix condyle Pelycosaur Dimetrodon Therapsid Thrinaxodon Mammal Felis

10. Feeding 1) expansion of temporal opening, elaboration of jaw muscles 2) reduction in post-dentary jaw bones, “second” jaw articulation 3) tooth specialization (heterodonty) Breathing 1) secondary palate 2) reduction in lumbar ribs, formation of ribcage (& diaphragm?) 3) nasal turbinals (temp. & water conservation) Posture & locomotion 1) double occipital condyle, atlas & axis 2) enlargement of limb girdles 3) specialization of lumbar & sacral regions 4) vertical orientation of limbs 5) formation of a heel bone Hearing 1) reduced size & flexible attachment of post-dentary 2) reduction in size of stapes MAMMALIAN “GRADE” TRENDS IN CYNODONTS

11. LOBE-FIN AMPHIBIAN PELYCOSAUR FISH MAMMAL AMPHIBIAN CYNODONT Evolution of the ear

12. Synapsids -- size and position of stapes Sphenacodont pelycosaurs Advanced cynodonts

13. Synapsids – reduction of post-dentary jaw elements ( lateral views) Dimetrodon primitive theriodont primitive advanced cynodont cynodont Morganucodon primitive therian

14. Therapsid – mammal ear transition

15. Sorex (Recent shrew) – ear region TYMPANIC (angular) MALLEUS (articular)

16. Synapsids -- jaw machanics

17. Trithelodont (Ictidosaur) Jaw mechanics - development of double articulation

18. Early mammal (or proto-mammal?) Morganucodon (late Triassic)

19. MORGANUCODONTS vs ADVANCED CYNODONTS

20. CONTRASTS BETWEEN LATE TRIASSIC VERTEBRATES EARLY DINOSAURS medium-large sized herbivores & carnivores probably diurnal, some endothermic CROCODILES small-medium sized, carnivores LATE THERAPSIDS Small-medium sized, probably nocturnal herbivores (tritylodonts) insectivores (ictidosaurs) carnivores (cynodonts) EARLY MAMMALS Very small Insectivores probably nocturnal, endothermic

21. Coelophysis (carnivorous dinosaur) Tritylodon (herbivorous therapsid) Morganucodon (insectivorous “mammaliaform”) 3 meters 1 meter 10 cm Plateosaurus (herbivorous dinosaur) 10 meters LATE TRIASSIC VERTEBRATES

23. Late Permian (250 mya) Late Triassic (210 mya) Pelycosaurs & early therapsids (worldwide) Cynodonts (worldwide) Earliest mammals (Laurasia)

24. Late Jurassic (150 mybp) Late Cretaceous (70 mybp) Diversification of early mammals (Eurasia & N. Amer.) Origin & diversification of therians (worldwide) Isolation of southern groups