However, the echidna possesses 2 distinct corpora spongiosa separated by a septum, each of which surround the urethra only distal to the initial urethral bifurcation in the glans penis. The corpus cavernosum is well supplied with blood, extends up to the base of the glans penis and is primarily responsible for erection. This study confirmed that the echidna penis contains many of the same overall structures and morphology as other mammalian penises and a number of features homologous with reptiles. Despite this, only a few historical references describe the structure of the echidna penis and none provides an explanation for the mechanisms of unilateral ejaculation. The echidna penis consists of 4 rosette glans, each of which contains a termination of the quadrifurcate urethra, but it appears that only 2 of the 4 glans become erect at any one time. There are differences between echidna and platypus phalluses, but both are somewhat similar in structure to the reptilian phallus. One in particular is their penile morphology. Introduction of domestic species (eg.Monotremes diverged from therian mammal ancestors approximately 184 million years ago and have a number of novel reproductive characteristics.Later, more extinctions when Europeans reached Australia.Massive extinctions in Australia that may be the result of colonization by aboriginal humans.Marsupial moles (fossorial, insectivorous, vestigial eyes, Tails very large, used for propulsion and supportĢ) Molars replaced from the rear (up to 9 of them).Limbs are highly specialized for cursorial locomotionģ) 4th digit most important 5th large also.Ecological equivalents of antelopes and deer.Order Diprotodontia, Family Macropodidae.Some species convergent with flying squirrels.Long, furry tail that is never prehensile.Opposable, clawless hallux (for climbing?).Digits are either didactylus (separate ancestral state) or syndactylus ("fused toes").Teeth are either diprotodont ("two front teeth") or polyprotodont ("many front teeth"). ![]() New classifiation system based on incisor teeth and digits. What used to be the "order Marsupialia" is now 7 separate orders.Later: low protein, high fat (for rapid increase in mass).Early: high protein, low fat (for structural development).Milk changes composition during lactation.Leaves pouch at weight roughly equivalent to birthweight of a similarly-sized placental.Teat swells in its mouth to make a semi-permanent attachment.Move to pouch or (if pouchless) grab ahold of teats.Well-developed front limbs for grasping fur.Heart: incomplete separation of the ventricles.Young born extremely small relative to adult size.Brains are relatively small and not very convoluted.Different numbers of incisors on top and bottom.Epipubic bones (both sexes whether or not they have pouches).50% have pouches (marsupia) form of pouch varies with ecology: kangaroo-opens up top bandicoot (diggers)- opens on bottom.Hair at 7 weeks, eyes open at 9 weeks, suckled for 16 weeks.Male and female burrows close together or shared.Eats aquatic crustaceans, insect larvae, earthworms.Claws for digging ( web extends past claw)Īlso present on male echidnas, but unknown whether they are venomousĭuck-like rostrum covered with moist leathery skin contains electroreceptors on its front edge.At 12 weeks eyes open and baby leaves pouch for burrowģ) Eyes and ears lie in folds of skin and are covered when underwater.After hatching it lives in its mother's pouch for 12 weeks.Lay (usually) 1 egg that hatches in 9 days.Become torpid in cold temperature/low food availability. ![]() Structure may be supported by epipubic bonesġ) Digging down 2) Passively by rolling into a ball and exposing spines
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