Crosopterygian or Crossopterygian: How To spell?
The word Crosopterygian is misspelled against Crossopterygian, a noun meaning "One of the Crossopterygii."
Crossopterygian has double "ss" is mispronounced as "s"Remember double 'SS' in between the strings cro & opterygian which should not be misspelled with single 'S'
Wrong Spelling:  cro-s-opterygian  Correct Spelling:  cro-ss-opterygian 
Find more incorrect spellings of Crossopterygian to spell right way.