Fair enough.Btw., if a discussion about this phenomenon is going to develop in here, could the next debater start a new thread in the pronunciation section? Let's leave this one for recordings and reviews (also, so I don't get notifications).
- You said the o in credo was long, but I actually think there is some leeway. It seems to be anceps. final -o in ablative/dative singulars is always long, but you find quite a few examples of short final -o in nominatives (nemo*, Sulmo**, caro etc.), in 1st person singulars (nescio***), in some adverbs, at least if they're iambic (cito**** <> citō), and I think also in future imperatives ending in -to (although I can't think of one off the top of my head) or in words like quando
With some originally iambic words (like modo or ego), the long final o had even become very unusual by classical/Augustean times.
It seems like -ō was the standard pronunciation, but -ŏ was at the very least not unusual. It seems a little bit more colloquial, but if you give mihi without final length, you should accept the short o as well
* Ov. tris. 2, 349f.
Sed neque me nuptae didicerunt furta magistro,
quodque parum nouit, nemŏ docere potest.
** tris. 4, 10, 3 Sulmŏ mihi patria est (...)
*** Cat. 85 nesciŏ sed fieri (...)
**** Ov. tris. 3, 3, 29f.
Si tamen inpleuit mea sors, quos debuit, annos,
et mihi uiuendi tam citŏ finis adest
The reading is very uncertain, but there may be an exception to this in Vespa's Iudicium Coci et Pistoris (which uses short final -o almost as much, if not more, than long final -o):
Sīcut Neptūnō, fervent in cācabǒ flūctūs.
But there's all sorts of other readings, or attempts to make it scan better.
- crēdō <- yeah, sure, won't that be just some poetry, metrī causā etc. ?
Well, it struck me that it was extremely rare with -o signifying a singular dative or ablative. If you find a rare example of such an -o being short, as Dantius provided, then you could indeed argue for metrical coercion (or whatever it's called in English).
As opposed to that, a shortened final -o in the 1st pers. singular (and other instances) seems to occur comparatively often, so I find it hard to argue that it's just a matter of the metre (metre is usually a pretty weak argument, anyway, I would say).
In most cases the shortened final -o is from 'iambic' shortening, isn't it? In later texts (eg. Symphosius' riddles) it spreads to ō after a heavy syllable as well, but this is hardly a classical phenomenon.
mihi is found very early, and is pretty much regular; at least, 38x in the Eclogues vs. mihī 3x (of course, the former might just be more convenient in hexameter). crēdō is obviously rarer in Vergil, but the two instances in the Georgics and Eclogues both scan - -.
nescio does come under iambic shortening, because it originally terminated u -. nēmo can probably be explained by analogy (or because it originally derives) from homo (< homō < hemō), given that nēmō < *nehemō.From the examples I gave above, only cito could be explained by iambic shortening. Words like nemo, Sulmo, Naso, nescio are not iambic.
And regarding iambic shortening: As I said, that feature did not just seem to be a poetic licence, but something that seemed pretty common in regular speech as well, to the extent that some formerly iambic words (like modoor ego) had completely dropped the length on the o by Augustean times.
I've also noticed that some dictionaries (like Georges or Lewis & Short) give words like crēdo without the length on the o.
I'm not suggesting that iambic shortening was a poetic license. It was evidently (and presumably first of all) a feature of the spoken language.
Lewis and Short (or the online version, at least) quite often fails to mark quantities; in fact, I don't think it ever marks o as long in a final syllable, even when it clearly is.
But in fact you're completely right that crēdo is acceptable, as it appears in Ovid Ep. ex Pontō 1.7.56: sed fuit īn fātīs hoc quoque, crēdo, meīs. My mistake, I didn't realise that the change started this early. Admittedly this is against 6 instances of crēdō in Ovid (and one can add three certain instances of crēdō in the Aeneid to the Vergilian evidence above), so I doubt it can be regarded as standard.