2. Early Mammals: Morganucodontids

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

4. Discovered in China a few years ago Mammalian pectoral girdle
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.

5. Triconodonts cont.,
Repenomamus giganticus

6. Early Mammals: Multituberculates
Kryptobataar.

7. Multituberculates cont.
Ptilodus
Ptilodus- arboreal adaptations (sharp claws, mobile, reversible foot, prehensile tail) Canada

8. 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)

9. Early Mammals: Recent finds
Bishops, Ausktribosphenos

12. Prototheria
Eutherians
Metatherians
Pantotheres
Trichodonts
Multituberculates
Monotremes
Morganucodontids

13. Monotremes

14. 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

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

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

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

18. Monotremes: Primitive characters
Coracoid- fused with scapula as ‘corocoid process’ in most mammals
Together with scapula, form joint for insertion of proximal end of humerus

20. Monotremes: Primitive characters
Reproductive characters

21. Monotremes: Derived characters

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

23. Tachyglossidae - continued
Tachyglossus aculeatus
Atelerix frontalis
Zaglossus bruijni

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

25. Ornithorhynchidae (Platypus) Ornithorhynchus

26. Grant et al 1998

27. Grant et al 1998

28. Grant et al 1998