in subclass Protheria

• spur on male ankles
• electroreceptors on bill/beak
• edente (no teeth)
• 2 unfused uteri
• one urinary/digestive/reproductive opening

[image]

cloaca: one urinary/digestive/reproductive opening

small eggs (>1in), 10-11 day incubation period, hatch via egg tooth, hatchlings have well developed shoulders and forelimbs, blind with no hindlimb development

young suck milk from mom's fur

O. Monotremata

Echidnas

short beaked echidnas: myrmecophagous (eat ants and termites)

long beaked echidnas: eat earthworms and arthopods

panniculus carnosus muscle allows them to curl up in a ball (defensive position) (this muscle usually paired with spines)

O. Monotremata

Platypus

eats aquatic invertebrates

soft leathery bill with electroreceptors for detecting prey

food is masticated via keratinized pads

males have venemous spurs on hind feet (competition)

• cervical ribs (neck)
• no vibrissae
• lay eggs
• lowest metabolic rate of any mammal (not as homeothermic, not great endotherms) 
• pectoral girdle far more complex