[GSlob]

Aquatic mammals normally have very durable furs: hats and coats could easily last 20+ years, but this "Castorcauda lustrasimilis, a docodont mammaliaform" beat all the records. Why, it was "preserved with fur" for how long? Since Jurassic?

[VadeRetro]

As I read the article, the fur wasn't preserved in the sense of still having the fur. Traces were visible sufficient to identify guard hairs and normal body fur.

[Tax-chick]

Aquatic mammals normally have very durable furs

So do some non-aquatic mammals. I had a mink cape that was 35 years old when I gave it a friend who actually had occasion to wear a mink cape :-).