Caenagnathus

Caenagnathus ('recent jaw') is a genus of oviraptorosaurian dinosaur from the late Cretaceous (75 million years ago). It is known from a single lower jaw, found in the Dinosaur Park Formation of Alberta, Canada.

Classification
This dinosaur has a confusing history. In 1936, a set of jaws were found, and later given the name Caenagnathus, meaning 'recent jaw'; they were first thought to be those of a bird.[1] In 1988, a specimen from storage since 1923 was discovered and studied. This fossil were used to link the discoveries of several fragmentary oviraptorosaur species into a single dinosaur, which was assigned to the genus Chirostenotes, originally named for a pair of hands that were long considered to come from the same animal as Caenagnathus. Since the first name applied to any of these remains was Chirostenotes, this is the only name that is recognized as valid.[2] However, further study cast doubt on the idea that all of these fossils belonged to the same creature: while Chirostenotes was an advanced oviraptorosaurian and possibly an oviraptorid, Caenagnathus was shown to have been a more primitive animal.[3]

Recently, it was found that Caenagnathus is probably the closest related genus of Anzu. The possible species, found in the study to be "Caenagnathus" sternbergi, was found to be sister taxon to the grouping of Anzu and Caenagnathus collinsi. When species known only from limb bones, such as the potential synonym Chirostenotes pergracilis, were included in the analysis, the relationships among these species became unresolved. The authors of the analysis stated that further study would need to be done in order to match species known from limb bones with those known from jaw bones as potential synonyms.