Wikipedia
Zapsalis is a genus of dromaeosaurine theropod dinosaurs. It is a tooth taxon, often considered dubious because of the fragmentary nature of the fossils, which include teeth but no other remains.
The type species is Zapsalis abradens, from the Judith River Formation of Montana, dating to 75 million years ago, during the Campanian stage. Additional teeth attributed to Z. abradens have been found in the Dinosaur Park Formation, also dated to about 75 Ma ago. While Zapsalis-like teeth have been found in other formations dating to various time periods and assigned to this genus, they most likely belong to new genera and species.
In 1876 Edward Drinker Cope named Zapsalis abradens based on a tooth found in Montana, presently specimen AMNH 3953. The generic name is derived from Greek za~, "thorough", and psalis, "pair of scissors". The specific name means "abrading" in Latin.
In 1964 Richard Estes synonymised Zapsalis with Paronychodon, but in 2002 Julia Sankey e.a. concluded the teeth represented a separate "?Dromaeosaurus Morphotype A". In 2013 Derek Larson and Philip Currie recognised Zapsalis as a valid taxon from the Judith River and Dinosaur Park Formation. The teeth are typified by a combination of rounded denticles, straight rear edge and vertical grooves. Similar teeth from the older Milk River Formation were referred to a cf. Zapsalis.