Orders Monotremata, Marsupialia, & Insectivora Subclass Prototheria (pro = before; theria = "to suck") Order Monotremata (the Monotremes) - Monotremata = "one opening" in reference to the cloaca cloaca: also found in all reptiles; chamber into which the digestive, reproductive and excretory tracts open and pass their products - Remaining members of a lineage which separated early in evolution of Class Mammalia - Only surviving taxon of this subclass - Consists of 2 families & 3 living genera - Resemble reptiles more than any other mammals Family Tachyglossidae (echidnas or spiny anteaters) - Australia, Tasmania, New Guinea - Fur intermixed with dorsal, barbless spines (protection) - Large claws, fossorial - Diet = insects - During breeding season, females develop temporary pouch on abdomen; one egg transferred into pouch; young hatches & remains in pouch for 6-8 wks Family Ornithorhynchidae (duck-billed platypus) - eastern Australia & Tasmania - inhabits freshwater streams, lakes, etc... - streamlined & dorsoventrally compressed body; webbed feet - Diet = crustaceans - mechanoreceptors & electroreceptors in bill - female lays eggs & incubates them in a bank burrow; no temporary pouch General Characteristics of Monotremes: 1.) No teeth in adults; horny plates in adult platypus 2.) No well-formed nipple, but have mammary areas 3.) No vibrissae 4.) Lay shell-covered eggs which are incubated & hatched outside the mother! 5.) Cloaca a. females - oviducts open into cloaca b. males - penis on ventral wall of cloaca; testes abdominal 6.) Have hair, 4-chambered heart, & are endothermic (lower body temperature than other mammals) 7.) Long rostrum covered with a rubbery & sensitive skin 8.) Males have horny spurs on ankles; associated poison gland 9.) epipubic or marsupium bones in pelvic region (similar to marsupials) - unknown function; remnant of reptiles? Subclass Theria Infraclass Metatheria (meta = middle) Order Marsupialia (the Marsupials or pouched mammals) - One family in N. Amer. General Characteristics of Marsupials: 1.) choriovitelline placenta (yolk-sac placenta) 2.) abdominal pouch (= marsupium) 3.) nipples with mammary hair in pouch 4.) bifid vagina & uterus and bifid penis 5.) epipubic bones 6.) teeth 7.) short gestation / long development period 8.) < 5 incisors in each half of upper jaw < 4 incisors in each half of lower jaw Family Didelphidae Genus Didelphis Species Didelphis virginiana (Virginia opossum) 12-13 day gestation period! generalist; range expansion Skull: - long rostrum - narrow & small brain case - prominent sagittal crest Teeth: - large canines - upper incisors = conical, small, unequal - molars = tribosphenic - dental formula = 5/4, 1/1, 3/3, 4/4 = 50 total!!!! Specimen: - 5 digits with sharp claws, except 1st toe on hind foot = clawless, opposable - cat-size - gray, black/reddish color - underfur & white-tipped guard hairs - may have 3 dark streaks on head - most of tail = naked, scaly Infraclass Eutheria (true placental mammals) Order Insectivora (the Insectivores; shrews & moles) - Most primitive of the eutherians Family Soricidae (shrews) - mouse-like / small (2.5 - 180 g) - long snout - small eyes - no baculum - Some have odor glands on flanks - Zygomatic arch absent or reduced - No tympanic bulla - anteriormost incisors = forcep-like - W-shaped (dilambadont) molars - Pigmented teeth Genus Sorex Sorex cinereus (masked shrew) Sorex longirostris (southeastern shrew) Sorex fumeus (smoky shrew) Sorex dispar (long-tailed shrew) Sorex palustris (northern water shrew) Sorex hoyi (pygmy shrew) Genus Blarina Blarina brevicauda (short-tailed shrew) Genus Cryptotis Cryptotis parva (least shrew) Family Talpidae (moles) - wide, large hands/long claws (fossorial) - velvety fur - small eyes - teeth unpigmented - zygomatic arch & tympanic bulla present - no baculum Scalopus aquaticus (Eastern mole) Condylura cristata (star-nosed mole) Parascalops breweri (hairy-tailed mole) Primitive Mammals 3 Orders Monotremata Marsupialia Insectivora Characteristics: 1.) resemblance to ancestral reptiles 2.) ancient phylogeny 3.) > 40 teeth 4.) molars = tribosphenic or dilambadont .