Some taxanomy(?) or is it zooology questions.

[Raging Epistaxis]

Reasons for a sap eater / sap producer relationship that have at least some basis in reality:
- Perhaps the plant has an organ which the sap eater stimulates to release spores/pollen/seeds, thus aiding reproduction. EX: pick a flower, any flower...
- The sap itself could contain reproductive elements that are then distributed by the sap eater in feces or by mechanical spread. EX: pick a berry, any berry...

Less symbiotic, but no less realistic:
- the sap producer also has toxic elements - alkaloids, etc - that the sap eater utilizes as a toxic defense. Ex: Many insects, perhaps most famously, Monarch butterflies

Or perhaps some synthesis of realistic and fantasy elements: I'm envisioning something like a 40-50# Koala with an even nastier attitude, razor sharp claws, and venomous to boot ... maybe natural camoflage that makes them practically invisible when in their preferred plant and sitting still like a Sloth.
Ok, that's bigger than most Rhesus, at least the ones I've worked with, but still...
The forelimbs could be extremely heavily muscled, with the claws being used both to help the creature hold onto the plant and to gouge out furrows for feeding, or to penetrate the hard shell that protects the sap rich interior. As far as tongue structure, perhaps rasp-like (as demiurge suggested) or a hollow tubelike structure, or a bit of both: a tube with a (retractable) barbed outer surface to help it stay in place while feeding.

HTH

R E

 

[blargney the second]

This is a very interesting thread, Ferret! Where are you trying to go with it?

Speaking of weird zoology, you've inspired visions of abominations that are part vertebrate, part invertebrate with an exoskeleton.

-blarg

 

[Ferret]

In a campaign world I'm creating I'm assembling some creatures that are not influenced by magic (perhaps indirectly), and these evolved from monkey like creatures that have one fore arm for eating insects and sap and on for holding on.

The sap eating is what they eat, because I want to hold onto a very gaunt appearence they lay egg sacs that hang from trees with a possible placenta attached to the trees phylum(that the ones with sap yes?). And I've alreadt mentioned the arms.