Thylacosimia: Marsupial Monkeys

Marsupial Monkey art done by Tortoiseman on reddit

Thylacosimia (family Thylacosimiadae) also known as the Marsupial Monkeys are fully arboreal descendants of the Common Brushtail Possum. They are found along the forested coast of Australia.

Biology

The average thylacosimia weighs about 30 pounds, has 2 foot long limbs and is 4 feet tall in height.

Marsupial Monkeys converge on the standard primate body plan with characteristics such as long spindly limbs, long fingers and toes, mobile joints and high dexterity. They also developed a flexible spine and neck to make navigating the trees easier. 

They are completely diurnal, though some still basal species still come out at night. Their eyes are relatively the same size albeit smaller, their whiskers are completely reduced, their ears are slightly smaller, but they still retain their strong sense of smell.

Thylacosimia have a diet of fruit and leaves, which they collect with their opposable thumbs/toes. They can also collect food and hang onto branches using their long, prehensile tail which is far stronger than their ancestor's. This tail only has a thin coat of black hair with a small fingerprint-like pad on the end. The joeys weigh the female down, so the tail of the female thylacosimia has 2 small eyespots made out of hair to make it look like a snake in order to scare off predators.

There are also a few changes to the pouch. Due to jumping around and climbing, the babies tend to fall out. In order to counteract this, marsupial monkeys  have pouch muscles that seal the joey in with a small breathing hole in the top.

Behavior

Marsupial Monkeys live in clans of about 5-10 individuals. The leader is male and the rest are female. The male declares his domain and females by urinating or defecating in the community nest. They also engage in coprophagia when times are tough to regain lost nutrients.

Clans have grooming-based hierarchies with the lower ranks cleaning the higher ranks all leading up the to the patriarch.

Gestation takes 2 weeks and they only come out of the pouch at 6 months old, they hit maturity at about 8 months. They live for about 12 years.

They aren't very bright and have the intelligence level of a cat.

Females may leave their joeys in another females pouch to nurse at the nest whenever it gets too dangerous to carry it around while foraging. While out foraging, the female will sometimes store food in her pouch granted the joey isn't in there.