Early Mammals Morganucodontids Morganucodon Early Mammals Triconodonts Jeholodens

Early Mammals: Morganucodontids Morganucodon

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

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.

Triconodonts cont. , Repenomamus giganticus

Early Mammals: Multituberculates Kryptobataar.

Multituberculates cont. Ptilodus

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)

Early Mammals: Recent finds Bishops, Ausktribosphenos

M Prototheria M et on M or ul tit ho do ot re m es ga nu co d on tid s Pa M Tr ic nt s at ub nt er cu la te s ot ns a ri he ria he ns re s he t Eu

Monotremes

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

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

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

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

Monotremes: Primitive characters

Monotremes: Primitive characters Reproductive characters

Monotremes: Derived characters

Tachyglossidae Echidnas (2 G, 2 s)

Tachyglossus aculeatus Atelerix frontalis Zaglossus bruijni Tachyglossidae - continued

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

Ornithorhynchidae (Platypus) Ornithorhynchus

Grant et al 1998

Grant et al 1998

Grant et al 1998