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Morganucodon

Early Mammals: Morganucodontids. Morganucodon. Early Mammals: Triconodonts. Till recently, known only from teeth and a few other skeletal fragments. Similar to Morganucodontids, except the cusps are linear. Jeholodens. Triconodonts cont., Jeholodens. Discovered in China a few years ago

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Morganucodon

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  1. Early Mammals: Morganucodontids Morganucodon

  2. Early Mammals: Triconodonts • Till recently, known only from teeth and a few other skeletal fragments. • Similar to Morganucodontids, except the cusps are linear. Jeholodens

  3. Triconodonts cont., Jeholodens • Discovered in China a few years ago • Mammalian pectoral girdle • (scapula and clavicle only– loss of coracoids and interclavicle) • Pelvic girdle is still ancestral • ilium, ischium and pubis are separate, epipubic bones are present. • Sprawling posture – limbs not rotated under body. • Demonstration of mosaic evolution. • pectoral girdle is derived, but the pelvic girdle is primitive.

  4. Triconodonts cont., Repenomamus giganticus

  5. Early Mammals: Multituberculates Kryptobataar.

  6. Multituberculates cont. Ptilodus

  7. Early Mammals: Pantotheres • Paraphyletic- used informally • Mid Jurassic • Earliest bifunctional teeth - single cheek tooth with grinding and shearing function. • Tribosphenic molars, ( primitive tooth type for living mammals)

  8. Early Mammals: Recent finds Bishops, Ausktribosphenos

  9. Prototheria Eutherians Metatherians Pantotheres Trichodonts Multituberculates Monotremes Morganucodontids

  10. Monotremes

  11. Monotremes: Fossil Record Archer et al 1985 • Steropodon galmanii • 125 MYA (Lightning Ridge sandstone deposits, New South Wales) • Teeth resemble those of a juvenile platypus • Second find- Kollikodon ritchiei, 1995, suggests diversification by early Cretaceous

  12. Monotremes: Fossil Record cont. • Tertiary Fossils • Obdurodon insignis (1970), O. dicksoni (Archer 1992) • Miocene • Kept teeth at maturity • May have been terrestrial • Megalibgwiliaramsayi (Griffiths 1991), Zaglossus hacketti • Giant echidnas • Z. hacketti = largest monotreme ever

  13. Monotreme origins and distribution: Paleocene platypus tooth discovered in Argentina (Pascual, 1992)

  14. Monotremes • Often called ‘primitive’… a misnomer • Mosaics of primitive and derived traits Tachyglossus - short-beaked echidna

  15. Monotremes: Primitive characters

  16. Monotremes: Primitive characters Reproductive characters

  17. Monotremes: Derived characters

  18. Tachyglossidae- Echidnas (2 G, 2 s)

  19. Tachyglossidae- continued Tachyglossus aculeatus Atelerix frontalis Zaglossus bruijni

  20. Philosophical Transactions of the Royal Society of London. Series B, Biological Sciences No. 1372, Platypus Biology: Recent Advances and Reviews, Jul. 29, 1998, pp. 1057-1238 Ornithorhynchidae (Platypus) Ornithorhynchus

  21. Ornithorhynchidae (Platypus) Ornithorhynchus

  22. Grant et al 1998

  23. Grant et al 1998

  24. Grant et al 1998

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