trends in the evolution of mammalsbiology-web.nmsu.edu/~houde/history_of_mammals.pdf · 2017. 9....

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Trends in the evolution of mammals Movement of limbs under body to support body above ground Increased brain size Increased efficiency of mastication heterodont dentition expanded size and mechanical advantages of jaw musculature reduction and movement of “post-dentary bones” from jaw into middle ear

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Page 1: Trends in the evolution of mammalsbiology-web.nmsu.edu/~houde/history_of_mammals.pdf · 2017. 9. 22. · Trends in the evolution of mammals Movement of limbs under body to support

Trends in the evolution of mammals

Movement of limbs under body to support body above ground

Increased brain size

Increased efficiency of mastication

heterodont dentition

expanded size and mechanical advantages of jaw

musculature

reduction and movement of “post-dentary bones” from jaw

into middle ear

Page 2: Trends in the evolution of mammalsbiology-web.nmsu.edu/~houde/history_of_mammals.pdf · 2017. 9. 22. · Trends in the evolution of mammals Movement of limbs under body to support

Cross-section through head of Fish

Page 3: Trends in the evolution of mammalsbiology-web.nmsu.edu/~houde/history_of_mammals.pdf · 2017. 9. 22. · Trends in the evolution of mammals Movement of limbs under body to support

Cross-section through head of Tetrapod

Page 4: Trends in the evolution of mammalsbiology-web.nmsu.edu/~houde/history_of_mammals.pdf · 2017. 9. 22. · Trends in the evolution of mammals Movement of limbs under body to support

Homologies of Postdentary Bones

Fishes Amniotes Mammals (among amniotes)

Hyomandibula Stapes (= “columella”) Stapes (=“stirup”)

Quadrate Quadrate Incus (=“anvil”)

Articular Articular Malleus (=“hammer”)

Angular Angular Tympanic (=“ectotympanic”

or “tympanic ring”)

Dentary Dentary Dentary

blue – middle ear ossicles of mammals

green – bones of mandible (= “lower jaw”)

Page 5: Trends in the evolution of mammalsbiology-web.nmsu.edu/~houde/history_of_mammals.pdf · 2017. 9. 22. · Trends in the evolution of mammals Movement of limbs under body to support

Reduction of post-dentary bones in Synapsids

Page 6: Trends in the evolution of mammalsbiology-web.nmsu.edu/~houde/history_of_mammals.pdf · 2017. 9. 22. · Trends in the evolution of mammals Movement of limbs under body to support
Page 7: Trends in the evolution of mammalsbiology-web.nmsu.edu/~houde/history_of_mammals.pdf · 2017. 9. 22. · Trends in the evolution of mammals Movement of limbs under body to support

Mammalian Middle Ear Ossicles

Page 8: Trends in the evolution of mammalsbiology-web.nmsu.edu/~houde/history_of_mammals.pdf · 2017. 9. 22. · Trends in the evolution of mammals Movement of limbs under body to support

Increased mechanical efficiency of jaw use of enlarged braincase and temporal fenestra as areas of

enlarged jaw muscle origin

larger lever arm

movement of mandibular articulation anteriorly

arrow: vector of muscle contraction

early synapsid late synapsid

Page 9: Trends in the evolution of mammalsbiology-web.nmsu.edu/~houde/history_of_mammals.pdf · 2017. 9. 22. · Trends in the evolution of mammals Movement of limbs under body to support
Page 10: Trends in the evolution of mammalsbiology-web.nmsu.edu/~houde/history_of_mammals.pdf · 2017. 9. 22. · Trends in the evolution of mammals Movement of limbs under body to support

Ophiacodon late Carboniferous-Permian Pelycosaur

Page 11: Trends in the evolution of mammalsbiology-web.nmsu.edu/~houde/history_of_mammals.pdf · 2017. 9. 22. · Trends in the evolution of mammals Movement of limbs under body to support

Dimetrodon Permian Pelycosaur

Page 12: Trends in the evolution of mammalsbiology-web.nmsu.edu/~houde/history_of_mammals.pdf · 2017. 9. 22. · Trends in the evolution of mammals Movement of limbs under body to support

Dimetrodon skull

homodont dentition

mandibular

articulation

synapsid

temporal

fenestra

Page 13: Trends in the evolution of mammalsbiology-web.nmsu.edu/~houde/history_of_mammals.pdf · 2017. 9. 22. · Trends in the evolution of mammals Movement of limbs under body to support

Inostranscevia Permian Cynodont

Page 14: Trends in the evolution of mammalsbiology-web.nmsu.edu/~houde/history_of_mammals.pdf · 2017. 9. 22. · Trends in the evolution of mammals Movement of limbs under body to support

Lycaenops Permian Cynodont

Page 15: Trends in the evolution of mammalsbiology-web.nmsu.edu/~houde/history_of_mammals.pdf · 2017. 9. 22. · Trends in the evolution of mammals Movement of limbs under body to support

Thrinaxodon Triassic cynodont

tendency towards

heterodont dentition

increased area for origin

of masticatory muscles

ring-like shape of angular

post-dentary bone

Page 16: Trends in the evolution of mammalsbiology-web.nmsu.edu/~houde/history_of_mammals.pdf · 2017. 9. 22. · Trends in the evolution of mammals Movement of limbs under body to support

Morganucodon Triassic cynodont

Hadrocodium Jurassic cynodont

heterodont

Page 17: Trends in the evolution of mammalsbiology-web.nmsu.edu/~houde/history_of_mammals.pdf · 2017. 9. 22. · Trends in the evolution of mammals Movement of limbs under body to support

Multituberculates Jurassic-early Cenozoic

small non-Therian mammals that superficially would have resembled

rodents or insectivores

strange highly specialized heterodont teeth

Page 18: Trends in the evolution of mammalsbiology-web.nmsu.edu/~houde/history_of_mammals.pdf · 2017. 9. 22. · Trends in the evolution of mammals Movement of limbs under body to support

Eomaia oldest presumed Eutherian – lower Cretaceous of China

Page 19: Trends in the evolution of mammalsbiology-web.nmsu.edu/~houde/history_of_mammals.pdf · 2017. 9. 22. · Trends in the evolution of mammals Movement of limbs under body to support

Late Cretaceous

shrew-like

Therians of Asia

Asioryctes

Ukaatherium Ukaatherium

Page 20: Trends in the evolution of mammalsbiology-web.nmsu.edu/~houde/history_of_mammals.pdf · 2017. 9. 22. · Trends in the evolution of mammals Movement of limbs under body to support

Archaic Paleogene Eutherian Mammals e.g., Pantodonts

e.g., Condylarths

Page 21: Trends in the evolution of mammalsbiology-web.nmsu.edu/~houde/history_of_mammals.pdf · 2017. 9. 22. · Trends in the evolution of mammals Movement of limbs under body to support

Archaic Paleogene Eutherian Mammals

e.g., Creodonts

e.g., Oreodonts

Page 22: Trends in the evolution of mammalsbiology-web.nmsu.edu/~houde/history_of_mammals.pdf · 2017. 9. 22. · Trends in the evolution of mammals Movement of limbs under body to support

Early Paleogene Primates

Carpolestes

Plesiadapis