The word "cestracionts" may seem like a daunting spelling challenge, but it can be broken down into its phonetic components. The first syllable "ces" is pronounced like "sess," while "tra" is pronounced like "trah." The final syllable, "-cionts," is a combination of the sounds "see-awn-ts," with a slight emphasis on the "ts" at the end. Altogether, the correct pronunciation is "sess-tra-see-awn-ts." This term is believed to refer to a genus of sharks, specifically the cow sharks.
The oldest sub-family of sharks, mostly fossil.
Etymological and pronouncing dictionary of the English language. By Stormonth, James, Phelp, P. H. Published 1874.