Eighteen Famous Boxing Styles comes from ShengXiao Daoren's Shaolin's Transmission of Robe and Bowl manual. it is properly called Surnames of the Founders of Eighteen Styles.
These Eighteen styles are linked together with the Seven Maneuvers.
The manual states
‘Seven Maneuvers Gathered Within Continuous Fist Make The Eighteen Combinations. They are seven types of maneuvers that take the techniques of eighteen styles and combine them into a way that continuously interconnects without end.’
I don't think that this is now part of Shaolin. Here is an article on the Seven Maneuvers.
The Heavenly Taoist's Praying Mantis Strikes