15-Letter Words Matching ____I___R______

There are 13 15-letter words that match ____I___R______. 2 are common words, such as PREHISTORICALLY and PREKINDERGARTEN. A rarer one is SULFINPYRAZONES. In this set, A is the most frequent open letter (12 words). 4 words contain a doubled letter.

Full list 13

prehistoricallyprekindergartenchoriocarcinomagravimetricallynonhierarchicalpassifloraceousapolipoproteinscorticotrophinsdithiocarbamatepantisocraticalpantisocratistsplanimetricallysulfinpyrazones

About this list

Words
13 (2 common words)
Common example
prehistorically
Rare example
sulfinpyrazones
Doubled letters
4
Ending in S
5
Most frequent letter
A (12)

Questions

How many 15-letter words matching ____i___r______ are there?

13. 2 of them are common words.

What is a common example?

PREHISTORICALLY is among the common words in this set.