Looks good!
Weremylodon, anyone?
Weresloth
No. Appearing: 1-4
Armor Class: 5
Move: 6”
Hit Dice: 2+3
% in Lair: 65%
Treasure Type: O,P
No. of Attacks: 2
Damage/Attack: 1-4/1-4
Special Attacks: Nil
Intelligence: Low
Alignment Neutral
Size M
These creatures are generally inoffensive and spend much of their days eating leaves, sleeping, etc. If they gain surprise over an opponent (having rolled a 1-4 due to their silence and coloration), they will flee 50% of the time, and sit silently otherwise, waiting for the intruder(s) to leave. They will fight if cornered or wounded, using their claws.
Originally appeared in Dragon Magazine #40 (1980).
Well, it's Medium sized so we could use our Lesser Ground Sloth as the base animal.
However, it seems more likely this is meant to be a tree sloth (considering those aren't extinct!). Although there's no mention of a Climb speed, which lends some support to it not being arboreal.
Are their 3E stats for a tree sloth? If there are, we could do two weresloths, one for the ground and one for the trees.

(Dungeons & Dragons)
Rulebook featuring "high magic" options, including a host of new spells.