How did the contracted perfect passive work?

Question

I was shocked when I saw the word "latest" in a Latin book. The book's English translation implies it is related to "latus." The next word "alteque" would have suggested an adverb "late" + "-st," but I don't know of any "-st" suffix in Latin. Had it not been for the other occurrences of "-st," I would have dismissed it as a scribal error. I assume this "-st" is a contracted version of "est." Contractions might not be formal, but they are probably still classical.

I was going to hypothesize a set of three paradigms based on "possum," which is the archetypal word with "esse" inside where the prefix isn't from a preposition. The hypothesized contracted perfect passive would do to the -sus/-tus-stem what the perfect active does to the *-uus/*-vus/*-wos-stem. This should not be confused with the poetic syncopated perfect active, which deletes the u/v, and such syncopation would be impossible for the hypothesized pluperfect and future perfect lest they confusingly overlap with the active. A concern is that there aren't many examples attesting this.

Alternatively, did the contracted form inflect for gender? There are 4 occurrences of "captust". There are also "multumst" and "iactast" as mentioned by Reddit.

"Neccessest" occurs many times. However, it could be caused only by the indeclinable "necesse," because "ipsest" is also found. "necessum" unfortunately overlaps with the alternative declinable past participle. Google returns some but potentially low-quality results for "necesserit" and "necesserat."

What would you put for the contracted perfect passive's conjugation table?

Answer 1

"Latest" here is a contraction of "late est", with late an adverb, as you suggested: "...lātē est altēque videndum". There is no perfect passive involved here.

The same kind of contraction can affect est in perfect passive forms, e.g. traductast for "trāducta est" or scriptust for "scrīptus est", but there is no special association between this contraction and the perfect passive, and it doesn't apply to forms of esse other than est or sometimes es.

Contraction of est to -st or of es to -s can be found after words that end with a vowel or with -m (this pronunciation may have been possible even when the "e" was written, but it's hard to tell whether an author intended for the first or second vowel to be elided in that context) or after words that end in a short vowel + -s. Contraction after -s tends to appear only in early inscriptions or the manuscripts of early poets. (This seems to be related to the archaic dropping of word-final s before a consonant.) See Did poets elide across consonants?

This kind of contraction is quite different from the case of posse, which has become inflected as a single word despite the etymological origin of some forms from a fusion of pot- with a form of esse.