"Ursine" is an adjective (much like, say, bovine).
So, it's just a typographical error.
It's an important realization that, even in professional writing it is completely commonplace for typos to creep in. Here's a cartoon about the issue:
(Alert! Original contains vulgar language!)
There was a newspaper in the UK called the "Guardian" which was known in the trade as the "Gradian" because it had so many typos. I once saw cough Vulva for Volvo in the body copy of a newspaper ad for that fine brand, and that's in an expensive paid ad.
"scripts unlikely to change"
Nonsensical, commercial writing is edited continually, to remove typos.
"But by continuing using "Ursine" as a noun..."
No. It sounds exactly like the writer is uneducated. The situation couldn't be simpler.
(It's particularly embarrassing, if you will, when people "try to use fancy words" - and are clueless about them, particularly extreme examples such as: not even knowing if it is a noun.)
I'd simply read it out as Ursid, since it's a typo.
Note that it is totally commonplace for voice talent to simply correct a typo if you're reading from a script. Not even worth mentioning.
If the script said "I brought an ice cream at the shop," one would just read it out as "bought". You would never read the appalling mistake, since it's obviously nothing more than a typographic error.
Ditto, if a script has "aks anything you want" one would just read it as "ask".
Not a big deal right?