Sentence splitting in SC

I generally find it very hard to split the scentence into IC's and DC's , as a result i falter on questions .

" Fossils of the arm of a sloth found in Puerto Rico in 1991 , and dated at 34 million years old , made it the earliest known mammal of the greater Antilles Islands . "

Step 1 : Understand the meaning
a ) Fossils of the arm of a sloth were found in Peuto Rico in 1991 ,
--- 34 million years old .
As a results the sloth is now the earliest known mammal of the Greater Antilles Islands .

STEP 2 : Here is the problem with me breaking the sentences into clauses


1) Fossils of the arm of a sloth found in Puetro Rico in 1991 ,

2) and dated at 34 million years old ,

3) made it the earliest known mammal of the greater Antilles Islands .

My Analysis :

S-V : Recognizing the subject/ verb is a herculean task for me
In the sentence the Subject is Fossils , but i guess we dont have any verb ?
Am i right on this since i guess dated is a verb -ed modifier and made is not a verb .

Pronoun error : "it " refers to the fossils which would not make sense in this context since fossils cannot be oldest mammals .

I guess there are the only two errors in this sentence , kindly let me know if i am correct in my above analysis also how can i improve my sentence split , i really find it hard to do so .