Hesperonychus

Hesperonychus (meaning "western claw") was a genus of small, carnivorous dromaeosaurid dinosaur. There is one described species, Hesperonychus elizabethae; the type species was named in honor of the woman who collected it in 1982.[1] It is known from fossils recovered from the lowermost strata of the Dinosaur Park Formation of Alberta, dating to the late Cretaceous Period (Campanian stage) about 76.5 million years ago).

Hesperonychus is known from one partial pelvic girdle, holotype specimen UALVP 48778, collected by Dr. Elizabeth Nicholls in Dinosaur Provincial Park in 1982. The fossil remained undescribed, however, until Nick Longrich and Phil Currie published on it in 2009. A number of very small toe bones, including "sickle claws", in the collection of the Royal Tyrrell Museum may also belong to Hesperonychus. The gracile appearance of these toe bones makes it unlikely that they belonged to a member of Eudromaeosauria. Despite their small size, the pubic bones were fused, a characteristic of adult dinosaurs, indicating that the specimen does not represent a juvenile of a known species.[2]

Though known from only partial remains, Longrich and Currie estimated its total length at under one meter and weight at about 1.9 kilograms, making it one of the smallest known carnivorous dinosaurs from North America. The alvarezsaurid Albertonykus was smaller.[2]