Hello, desktop Tumblr it is time to talk about mammals again >:)
I can feel my roommate watching me over my shoulder...
also wow using grammerly on desktop is really annoying! but I can use titles???? woo!
I think I regret choosing desktop for this.... oh well! lets get into it
Ok so we left off talking about monotremes and I will have a post about their bones at some point I pinky swear I just need to figure out what I want to talk about. ok anyways today let's see what should we talk about hmm.... drumroll please.....
Metatheria!
So metatheria are the marsupials of the animal kingdom you've heard of a lot of them and I'm sure you know their calling card- pouches. but we are getting INTO it tonight guys heheheh
ok so some Latin facts- we know that protheria (monotremes) means 'first beast' but metatheria means "in-between beasts"
the first/oldest protheria we know about is the sinodelphys they are found mostly in Australia and South America due to a lack of placental mammals during the whole continental drift business.
ok so what makes a marsupial a marsupial? well let's get into a few relatively universal traits amongst them (remember folks nature doesn't read biology books so some of these are special or gone in certain groups)
so bones (BONES!!!!)
so the pelvic and jaw bones in a metathere are different than in eutheres (we will talk about them next teehee) they do not have a rounded angular process and it's instead spiky (here's a picture of a possum jaw for reference)
There are also extra openings in the back of the pallet and a smaller brain case their teeth are funky too! They have an extra set of incisors.
so I mentioned their funky pelvic bones but what I mean by that is their reproduction is wacko. so like monotremes they have a cloaca and not a vaginal and anal opening. this is why they're "in-between beasts" they have traits that are similar to both ends of the spectrum.
speaking of reproduction their cloaca is subdivided and they will hold eggs internally with a specialized membrane. this membrane surrounds the fetus more than an egg would with a floating placenta surrounding the fetus unlike in us this placenta isn't attached to a uterine horn. Their reproductive structure is also loopy... I'm not kidding look at this shit- this is a kangaroo reproductive structure
WEIRD! They have a pseudovaginal canal which is only there for birth and is part of the cloaca also keep an eye on that second uterus ill get into that more with kangaroos specifically
and it's only in females male reproductive structure is normal
their young are always born underdeveloped. they have an extended lactation period because of this with that special changing milk we mammals have that will deliver the perfect amount of nutrients needed.
so the babies are born super early but those ungrateful little turds have the immediate responsibility to get THEMSELVES into their mother's pouch. Mamma can't help you do everything little Joey.
I need to expand on this because it's fucking INSANE ok so like I said they are underdeveloped and I mean like VERY underdeveloped as in they do not have a full heart or brain yet!!!!! their lungs are just sacks and they don't have a jaw but they DO have a tongue and arms that they use to pull along their mother's hair to get to the milk. again- mama ain't helping you.
Ok i'm ending this here only because this is just general overview stuff and then I'm gonna get into specific species and families next staring with kangaroos :)
