ninthcouncil said:If in doubt, form a regular English plural (i.e. "Pegasuses" in this case). Don't take any notice of classics snobs telling you otherwise - so few people know Greek and Latin these days that expecting the application of their irregular plural formation on obscure English words is just stupid. Same goes for the split infinitive "rule", which is just a misguided attempt to apply Latin verb rules to English words.
Good call!