The beaver is in the main AtB book, as for the lemur, who knows
"If you want something done, ask. If you want something done quickly, ask, and then begin counting down from ten with no explanation."
- Mahatma Gandhi "Unit be the side of darkeness"
For Lemur, your best bet would be Mutants of the Yucatan and use the entry for the Kinkajous. They describe the kinkajous as "it looks more like some kinds of tree lemur". Maybe Aad in some sort of jumping power and then develop sone vestigal traits if using AtB.
