The second species, P. blackfeetensis, is based on a specimen in the Museum of the Rockies (MOR 454), which was described by another notable paleontologist, Jack Horner.
Druga vrsta, P. blackfeetensis, zasniva se na primjerku Muzeja Stjenjak (Museum of the Rockies) (MOR 454) , kojeg je opisao jedan drugi poznati paleontolog, Jack Horner.