Vulpes et Pardus de pulchritudine concertabant et, Pardo suam pellem versicolorem extollente, Vulpes, cum suam praeponere non possit, dicebat Pardo, “At quanto ego sum speciosior, et quam longe formosior, quae non corpus, sed animum versicolorem et variis notis insignem sortita sum?”Vulpes et Pardus
= As often, we meet the main characters in the opening words of the fable.
de pulchritudine concertabant
= The root cert-, meaning to decide something by a contest or a debate, comes from the verb cernere, "to discere."
et, Pardo suam pellem versicolorem extollente,
= The conjunction et lets us know that there is another clause coming up, after the first clause about the fox and leopard debating - but first, we have an ablative absolute clause intervening. The reflexive pronoun, suam, is being used here non-classically, not referring back to the subject of the main clause, but instead to the subject of this ablative absolute clause, the leopard.
Vulpes, cum suam praeponere non possit,
= Remember that we are waiting for a subject-verb clause that was introduced earlier by et, and with the word vulpes we get the subject of that clause - but we are still going to have to wait a while, since there is a cum clause that has intervened. The cum clause here has a subjunctive verb, which means that is not just telling us about an event, but instead gives us some insight into what the fox is thinking, the reason why she is going to say what she does to the leopard. Notice the feminine form of the adjective, suam, which lets us supply the implied noun from the previous clause: suam (pellem).
= At last, the verb that completes the clause introduced by et so long ago! Vulpes et Pardus de pulchritudine concertabant et ... Vulpes ... dicebat Pardo.
“At quanto ego sum speciosior,
= The use of the personal pronoun is redundant with the verb sum, showing us that it is here for emphasis, highlighting the contrast between "you," the leopard, and "I," the fox. The ablative quanto is being used to express the degree of difference with the comparative adjective: "How much more beautiful I am!"
et quam longe formosior,
= The adverbial phrase quam longe also expresses the quality of the comparative adjective: "how far more beautiful." The literal sense of distance expressed by longe becomes metaphorically generalized to express extension in any distinction: time, quantity, quality, etc. In later Latin, you can even find this adverb longe used as a synonym for valde, meaning "very."
quae non corpus, sed animum versicolorem et variis notis insignem
= The relative pronoun, agreeing with ego (= vulpes, hence feminine singular), supplies the subject of the clause, with non corpus, sed animum as the object... but we are going to have to wait for the verb.
= At last, the verb we needed! It's a deponent verb with seemingly passive forms, but don't let that fool you: it is a transitive verb, and can take an object, which is what we are looking for. There is a pretty elaborate parallel structure at work here: non corpus (versicolor et variis notis insigne sortita sum), sed animum versicolorem et variis notis insignem sortita sum.
Here is the illustration of the fable by Francis Barlow:
The Aesopus Ning is now open for business - so, for more fables and to share your questions and comments with others, come visit the Ning!