Is the U long or short in the forms ussi and ustus of the verb ūro?

Question

I'm uncertain about the length of the u in the perfect and perfect passive participle stems of the verb uro /uːroː/.

My research

• Lewis (1890) gives "ūrō ūssī, ūstus" but doesn't explain why.

• On the other hand, Lewis and Short leaves the vowel unmarked "ūro , ussi, ustum", which doesn't indicate any specific length.

• The Wiktionary entry for ūrō gives "perfect active ussī, supine ūstum", also with no explanation. (Unmarked vowels in Wiktionary are supposed to be interpreted as short, because unlike L&S, Wiktionary does not use breves.)

• De Vaan gives "ūrō" "ussī" and "ustum". I feel like I've seen De Vaan leave off macrons in closed syllables in some places, but in this case I am fairly sure that De Vaan really thought of the vowel as short, because a separate PIE form "*usto- 'burnt'" is given for the past participle (vs. the etymology "ouse/o- 'to burn'" given for the stem of the forms with a long vowel).

I don't know enough about PIE morphology to understand whether an alternation between *ou and *u, which looks like ablaut, would be plausible in this context.

Based on IE comparison, a short vowel seems to be expected in the p.p. participle, but not in the perfect

Wiktionary gives the PIE root as *h₁ews- (a form that agrees better with what I recall of a theorized phonotactic constraint against word-initial vowels in PIE). The Wiktionary entry for *h₁ews- does agree with De Vaan in showing a short u in the participle: the PIE form is given by Wiktionary as *h₁us-tós, yielding Sanskrit "उष्ट (uṣṭá)" as well as Italic *ustos.

However, it lists Latin "ussī" as a descendant of a supposed "s-aorist" form "h₁ḗwst ~ *h₁éws-n̥t", which is also supposed to be the source of Ancient Greek εὗσα, the aorist form of εὕω. As far as I can tell, neither the Ancient Greek form, nor the PIE aorist form that Wiktionary gives is a zero-grade form, so the alleged short u in Latin ussi does not seem to be explained by the etymology given in the Wiktionary article for *h₁ews-. I would expect PIE *ew to become Latin ū (I also can't think of a Latin sound change that would shorten ū to u in this context).

Leveling of vowel length between the perfect and perfect participle doesn't seem implausible (I forget the details of how these forms developed in Latin, but I remember learning that they influenced each other by analogy in at least some cases) but I don't know how we could know that leveling occurred for this verb, or that the short rather than the long vowel was leveled. To me, it also seems plausible to suppose that the past participle could have gained a long vowel by analogy with the present stem.

I was looking at the length of the vowel in some other verbs, and I saw that in iubeo, De Vaan says that leveling is supposed to have resulting in a short vowel being generalized from the perfect passive participle to both the perfect and the present stems.

Romance evidence doesn't seem clear

I haven't seen any evidence from the Romance languages that clearly points towards a short vowel in either form. Italian comburere has re-formed both the perfect (to comburei) and the past participle (to comburuto). There seem to be Romance reflexes of a derived verb ustulo, and the vowels I see in Italian "ustolare, brustolare" and French "brûler" look more consistent with a long than a short quantity in the Latin etymon.

Questions

What was the length of the u in ussi and ustus, and how do we know? More specifically, what reasons, if any, are there for thinking that ussi had a short vowel?

Answer 1

The double ss is evidence for a short vowel in ussi (at least at some point)

Just a short time after posting this question, I remembered a relevant fact. Even though there wasn't (as far as I know) a regular Latin sound change that would have shortened ū to u in this context, there was a Latin sound change that would have shortened ss to s after a long vowel (or diphthong). For example, haurio has the perfect hausī in place of haussī.

So the fact that we have <ussi> rather than <usi> /uːsiː/ is indirect evidence suggesting that the initial vowel in this form was short when the sound change from ss to s occurred. Schrijver 1991 notes that the double ss of the perfect ussī implies that the initial vowel was short in Latin, and Bennett 1895 applies the same reasoning to argue for a short vowel in the word jussī (iussī) (p. 66).

I don't know whether this evidence rules out the possibility of earlier /ussiː/ being replaced by /uːssiː/ at a time when the ss > s sound change was no longer active. I think that in the Classical Latin period, it was phonotactically possible for a long vowel to come before ss: as far as I know, sequences of that sort are believed to exist in certain contracted forms like amāsse (for amāvisse) and dīvīsse (for dīvīsisse).

Bennett cites Priscian for short u in ussi

As additional evidence for a short vowel in ussī, Bennett 1895 cites "Priscian (Keil i. 466. 6)" (p. 68). However, I would guess that it's not a good idea to put too much weight on this evidence, because Bennett indicates that Priscian gave unreliable testimony about the length of vowels in the perfect in some other cases ("Priscian lends the weight of his authority to such forms as trăxī, mănsī, dŭxī, which certainly had a long vowel in the best period" (Bennett p. 62)).

Explanations for how the short vowel developed

Bennett's entry for jubeō (p. 66) says that shortening in jussī is supposed to occur "in accordance with the principle explained in § 88", but §88 is about what has been called "littera"-type shortening (e.g. Juppiter, cuppa, littera, bucca) (p. 94), something that I doubt has much relevance to the form of perfect stems.

There is some discussion of the short vowel in the participle in Schrijver 1991. Schrijver confirms my understanding that ūrō's root would require an initial laryngeal to be phonotactically well-formed in PIE, and argues that *HuC- regularly yielded Latin uC-, and not Latin auC- (contra "Forssman 1982-3, 291, Ringe 1988, 432-3, hesitating") (p. 74). Schrijver marks the vowel in the p.p. participle stem as short (ŭstum) in accordance with this sound change. Schrijver also marks the vowel in the perfect ŭssī as short, but doesn't explain how it came to be that way.

Sihler 1995 does account for a short u in ussī by analogical alteration of original *ūssī to match an inherited short vowel in the participle ustus (Sihler §527).

Vowel length of the u in the participle

All of the sources that I've looked at agree that ussī had a short vowel. Most say that ustus also had a short vowel:

• Hale and Buck (1903) §180.1 gives ūrō, ussī, ustus and explicitly notes that the vowel in the participle and perfect is short, unlike the vowel in the present

• Laurent 1953 says that "Several CL verbs had short vowels in the past participle and perfect contrasting with long vowels in the present: the stressed vowels in past participles like CESSUM 'yielded' and USTUM 'charred' matched those in perfect CESSĪ and USSĪ but not those in pres. CĒDŌ and ŪRŌ" (p. 23).

However, Bennett 1895 gives ūrō, ussī, ūstus, specifying that ū in the p.p. participle is "acc[ording] to the Romance" (Bennett p. 61).

Works cited

Bennett, Charles Edwin. 1895. Appendix to Bennett's Latin Grammar for Teachers and Advanced Students.

Hale, William Gardner, and Carl Darling Buck. 1903. A Latin Grammar.

Laurent, Richard. 1953. Past Participles from Latin to Romance.

Schrijver, Peter. 1991. The Reflexes of the Proto-Indo-European Laryngeals in Latin.

Sihler, Andrew L. 1995. New Comparative Grammar of Greek and Latin.