Pterospathodus
Pterospathodus is an extinct genus of conodont from the Silurian period.The Telychian of Estonia can be defined by five conodont zones.
The Sheinwoodian is defined between the acritarch biozone 5 and the last appearance of Pterospathodus amorphognathoides. The global boundary stratotype point is in Hughley Brook in Apedale, U.K.