Caenagnathus ('recent jaw') is a genus of Caenagnathidae dinosaur from the late Cretaceous period (Campanian stage, about 75 million years ago). It is known from partial remains including lower jaws, a tail vertebra, hand bones, hind limbs, and pelvis, all found in the Dinosaur Park Formation of Alberta, Canada.
Description
Caenagnathus measured about long and weighed about .
It was a large oviraptorosaurian, with some specimens suggesting it achieved sizes comparable to its relative
Anzu wyliei. Like
Anzu, it had a toothless lower beak that was shallower in depth than those of elmisaurines. It also shared with
Anzu less gracile proportions than those of elmisaurines.
Like all oviraptorosaurs, it would most likely have possessed a coat of feathers.
Classification
This dinosaur has a confusing history. In 1936, a set of jaws (CMN 8776) were found, and later given the name
Caenagnathus, meaning 'recent jaw'; they were first thought to be those of a
bird.
In 1988,
Epichirostenotes was discovered and studied. This fossil was 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 was the only name recognized as valid for many years.
However, Senter and Parrish (2005) doubted the synonymy of
Caenagnathus with
Chirostenotes, noting that the maxillary remains included in the
Epichirostenotes holotype didn't overlap with CMN 8776. A cladistic analysis of Coelurosauria by Senter (2007) found
Caenagnathus to fall basally within Caenagnathoidea, while
Chirostenotes fell as a derived taxon related to
Elmisaurus.
[Senter, P (2007). "A new look at the phylogeny of Coelurosauria (Dinosauria: Theropoda)". Journal of Systematic Palaeontology. 5 (4): 429–463. .] (right)]]The status and relationships of Caenagnathus
to other caenagnathid oviraptorosaurians began to be resolved with the discovery of more complete specimens in 2014 and 2015. The description of Anzu wyliei in 2014 represented the first nearly complete caenagnathid, and helped to clarify the differences between the more fragmentary specimens. Phylogenetic analyses found Caenagnathus collinsi
to be more closely related to Anzu
than to Chirostenotes
. A second species which had previously been referred to Caenagnathus
, "Caenagnathus" sternbergi
, was found to be the sister taxon to the grouping of Anzu
and Caenagnathus
in one 2014 analysis.Caenagnathus collinsi
. These appeared to be intermediate in size and anatomy between the smaller Chirostenotes
and the larger Anzu
, lending support to their hypothesized relationships. These bones can be distinguished from Chirostenotes
and contemporary "Leptorhynchos" elegans'' by features of the limbs, specifically the hand and metatarsals.
A new Chirostenotes specimen described by Funston and Currie (2020) preserving a mandible provides further evidence that Caenagnathus is a distinct genus from Chirostenotes despite both taxa being part of the Caenagnathidae.[G. F. Funston & P. J. Currie (2020) New material of Chirostenotes pergracilis (Theropoda, Oviraptorosauria) from the Campanian Dinosaur Park Formation of Alberta, Canada, Historical Biology, ]
See also
-
Timeline of oviraptorosaur research
