Mammals Flashcards
Subclass Eutheria and orders
Subclass: Eutheria Order 1) Carnivora (sea lion, dingo) 2) Cetacea (whales, dolphins) 3) Chiroptera (bats) 4) Rodentia (rats and mice) 5) Sirenia (Dugong)
Subclass Prototheria and order
Subclass: Prototheria
Order: Monotremata (platypus, echidna)
Subclass Metatheria and order
Subclass: Metatheria (marsupials)
Order
1) Diprotodontia
2) Polyprotodontia
Mammalian phylogeny in order from oldest to youngest (3)
Oldest: Monotremes
Middle: Marsupials
Newest: Eutherian
Where are all monotreme fossils found?
Southern hemisphere
Were all on “ganduana” supercontinent
Monotremes and retained reptilian characteristics
1) Oviparity
2) Meroblastic cleavage of embryo
3) Produce venom (platypus)
4) Electroreception
Examples of Monotremes (2)
1) Platypus
2) Short-beaked Echidna
Defining features of Monotremes
1) Absence of calcified teeth
2) Electroreception
3) Reptile-like stance
4) Oviparity
5) No Teats
6) Venom
Absence of calcified teeth in monotremes
Develop molars but lose them
Replaced by keratinized epidermis
Milk production in female monotremes
No teat
Milk secreted onto fur
Young lap milk off the fur
Venom glands in monotremes are called?
Crural gland
Male Platypus venom gland
Crural gland Well developed in male platypuses Sharp keratinized spurs Medial aspect of tarsal joint Can move independently Venom production/use is androgen dependent
Electroreception in Monotremes
Located in the bill/beak of platypus
Less so in echidna
Scan for electrical disturbances
Monotreme Skull
Premaxilla forms the rostral bill in platypus
Monotreme Pectoral Girdle
Coracoids, epicoracoids and interclavicle
- reptilian features
- in eutherians, caracoid fused with scapula
Monotreme limbs
Right angle to body (reptilian feature, rotate in sockets to give mammalian gait)
Platypus “knuckle-walk” because of webbing
Chromosome numbers in platypus and echidna
Platypus (5X, 5Y) - male
Platypus (10X) - female
Echidna (5X, 4Y) - male
Echidna (10X) - female
Do monotremes have a SRY on Y chromosome?
No, no SRY on X or Y chomosome
Female reproduction in monotremes
Platypus: only left ovary is functional
Produce 1-3 eggs
Echidna: Both ovaries are functional
Only produce 1 egg
Large yolky eggs
Mammary glands but no teats
Marsupials (general info)
NOT primitive mammals
Most contain a pouch (marsupium)
Unique in their mode of reproduction
Sophisticated and successful adaptations
Do marsupials use lactation or gestation?
Lactation
Young are born very underdeveloped and depend on lactation
Lactation»_space;» Gestation
Marsupial chromosomes
XX - female reproductive + POUCH
XO - female reproductive + SCROTUM
XY - male reproductive + SCROTUM
XXY - male reproductive + POUCH
XX = pouch Y = Male SRY = testes determining gene
Eutherian Female Reproductive Tract
Ureters pass laterally to Mullerian ducts
Mullerian ducts fuse to form vagina
Marsupial Female Reproductive Tract
Ureters pass MEDIALLY to Mullerian duct
Mullerian ducts cant fuse
Two lateral vaginae from Mullerian ducts
Median vagina made of connective tissue
Median Vagina in Marsupials
Becomes patent just before parturition
May regress
May remain patent after parturition (ex macropods)
Sperm ascent lateral vaginae only
Marsupial Pouch
Pouch encloses teat and young
In species without pouch, young hang on
Marsupial Neonate
Hind limbs fetal paddles
No hair or vibrissae
Kidneys and gonads yet to differentiate
Periderm covers eyes and ears
