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Early Mammals: Morganucodontids

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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

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

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