2. Early Mammal Evolution -did not occur in a vacuum -lots of abiotic & biotic factors -Examine early mammal evolution in the context of the geological time scale

3. Synapsids -Mammal-like reptiles - Originated in Paleozoic era (about 320 Mya) - Branched early from other reptiles Amphibians Synapsids Mammals “Reptiles” & Birds Anapsids Diapsids Euryapsids ~320 MYA --Cotylosaurs-stem reptiles -main base branch of all later “reptiles” & mammals

4. Paleozoic Era (570-248Mya) Invertebrates flourish First vertebrates & land plants Mesozoic Era (248-65 Mya) “age of dinosaurs” first “true” mammals 2nd major radiation of insects radiation of angiosperms (flowering plants) oldermore recent Late Permian Mass Extinction ~248 Mya

5. Mesozoic Era (ca. 248-65 Mya) Cretaceous Jurassic Triassic ~248 200 140 PERIOD MYA since beginning of each period Therapsid reptiles Appearance of first true mammals about 220 mya Appearance of archaic mammals First marsupials and placentals -angiosperm radiation & 2nd insect radiation

6. Mesozoic Era (ca. 248-65 Mya) Ends with mass extinction (especially of dinosaurs) Meteor impact near Yucatan Peninsula? New Era: The Cenozoic “age of mammals” Mammals had been around for ~155 My Underwent a major radiation in the early Cenozoic Replaced dinosaurs as the dominant terrestrial vertebrates

7. Cenozoic Era (ca. 65 Mya-present) Quaternary Tertiary ~65 ~2 PERIOD MYA since beginning of each period Epoch Paleocene Eocene Oligocene Miocene Pliocene Pleistocene Recent (Holocene) Adaptive radiation of marsupials & placentals Appearance of modern Orders Appearance of modern Families Appearance of modern Subfamilies Appearance of many modern Genera Terminal Eocene Event Appearance of modern species or their antecedents Great Ice-age extinctions Modern species & subspecies Another mass extinction precipitated by man?

8. Synapsids -Mammal-like reptiles - Originated in Paleozoic era (about 320 Mya) - Branched early from other reptiles Amphibians Synapsids Mammals Reptiles & Birds Anapsids Diapsids Euryapsids ~320 MYA --Cotylosaurs-stem reptiles -main base branch of all later “reptiles” & mammals

9. A. Synapsids - one temporal opening 1. Led to mammals 2. Postorbital and squamosal bones articulate above hole B. Anapsids - no temporal openings 1. Primitive Condition 2. Led to turtles C. Euryapsids - one temporal opening 1. led to extinct marine reptiles 2. Postorbital and squamosal bones articulate below hole D. Diapsids - two temporal openings 1. led to lizards, snakes, and birds Vertebrate Temporal Fenestrae

10. 2 major groups of Synapsids -Pelycosaurs -Therapsids

11. 2 major groups of Synapsids -Pelycosaurs -Therapsids a. Anomodonts -herbivores

12. 2 major groups of Synapsids -Pelycosaurs -Therapsids a. Anomodonts b. Theriodonts -herbivores -much more diverse, primarily carnivorous

13. Therapsida- continued I. THERIODONTS Cynodontia -largest & most successful group of Theriodonts -existed for >>75 My (from late Permian to mid-Jurassic) Therapsids -many diverse families, later cynodonts included diverse herbivores & carnivores Developed many of the transitional anatomical features leading from MLR Mammals -much more diverse, primarily carnivorous

14. Transition from Cynodonts to Mammals 1. Marked reduction in body size Pelycosuar Advanced Therapsid 2. Increasing size of temporal opening

15. Transition from Cynodonts to Mammals 1. Marked reduction in body size Pelycosuar Advanced Therapsid 2. Increasing size of temporal opening 3. Temporal bar begins to bow out from braincase-zygomatic arch

16. 1 -all dentary! Pelycosaur Early Therapsid Early Cynodont Later Cynodont Progressive loss of bones in the lower jaw Jaw bones & hinge become bones of the middle ear in mammals

17. Dentition becomes increasingly complex HOMODONTHETERODONT Examples of more complex dentition in early mammals

18. Pelycosaur Cynodont Air enters front of mouth Air enters back of mouth

19. amphibian reptile mammal

20. Loss of lumbar ribs

21. MESOZOIC Remember... This is very early on in mammalian evolution

22. First mammals in Late Triassic (~220+ Mya) Major Radiations Modern Orders Appear MESOZOICCENOZOIC Triassic Jurassic What has happened over the last 150-200 My?

23. SC: Prototheria IC: Metatheria SC:Theria monotremes marsupials placentals IC: Eutheria SC=Subclass (there are two in Class Mammalia) IC = Infraclass (there are two within Subclass Theria 5 species 285+ species 5,200+ species

24. MESOZOIC SC: Prototheria IC: Metatheria IC: Eutheria SC:Theria CENOZOIC Cretaceous Jurassic Triassic Cynodonts MONOPHYLETIC ORIGIN single dentary bone, squamosal-dentary articulation monotremes marsupials placentals ?

25. MESOZOIC SC: Prototheria IC: Metatheria IC: Eutheria SC:Theria CENOZOIC Cretaceous Jurassic Triassic Early Prototherians Cynodonts monotremes marsupials placentals

26. Early Prototherians Order Triconodonta- -small & carnivorous/ insectivorous, -molars with 3 cusps arranged in a row -size of house cat

27. Order Multituberculata Early Prototherians -most successful group of mammals ever (100 MY) -very diverse, all small -resembled therian rodents-incisor pair & diastema -Convergent Evolution Gnawing -probably outcompeted by true rodents

28. Reconstruction of Ptilodus, a multituberculate

29. An unnamed multituberculate standing on an image of its lower cheek teeth

30. Early Prototherians Order Triconodonta Order Multituberculata Extinct by ~20 MYA see clear signs of heterodonty that first appeared in late cynodonts Order Monotremata -only living order of the Subclass Prototheria

31. MESOZOIC SC: Prototheria IC: Metatheria IC: Eutheria SC:Theria CENOZOIC Cretaceous Jurassic Triassic Early Therians Cynodonts monotremes marsupials placentals

32. Early Therians -lineage that led to all other mammals (including marsupials) Family Peramuridae A different type of Heterodonty than in Prototherians basic pattern for all later Therian Mammals tribosphenic molars appear

33. Tribosphenic molars Occlusion Trigonid Talonid basin

34. Summary Mammals have been around for a long time Mammals evolved from Synapsids temporal opening Cynodonts- advanced Therapsids Early therians - many transitional features tribosphenic molar Late Trassic -including early heterodont dentition Early Prototherians - multituberculates, triconodonts--simple heterodont basic pattern for later Therians