רבי נחמיה אומר מכסה אחד היה ודומה כמין תלא אילן והא תלא אילן טמא הוא ה"ק כמין תלא אילן הוא שיש בו גוונין הרבה ולא תלא אילן דאילו התם טמא והכא טהור
R' Nechemya says: It was a single cover, and looked like a תלא אילן. [The Gemara asks:] But a תלא אילן is tamei. He said it's like a תלא אילן, in that it has many colors, and not a תלא אילן, because that is tamei and this (the תחש) is tahor. (My rough translation)
There has been considerable discussion on what the תחש is (see Hebrew Wikipedia for examples), but none that i could find on the תלא אילן. Google searches for תלא אילן keep coming up with the discussion about the תחש here.
I did find one online dictionary that suggested it's a squirrel, but squirrels don't seem all that colorful.
I would suggest a giraffe (one of the suggestions for what a תחש is), but giraffes are tahor.
Has there been any research into what a תלא אילן is?
Please only post answers sourced in scholarly research, not personal conjecture. Feel free to give your ideas in comments though.