Describer

Sternberg, 1940

Time

Cretaceous Late Campanian

Classification

Saurischia Theropoda Tetanurae Coelurosauria Oviraptorosauria Caenagnathidae

Diet

Carnivore

Fossilsite

Judith River Group (Wedge), Alberta, Canada

Fall Under

Caenagnathus

Info

Typespecies

Caenagnathus (Sternberg, 1940) > Caenagnathus collinsi (Sternberg, 1940) > Caenagnathus sternbergi (Cracraft, 1971)

Mandible

Barsbold 1983

Holotype

NCP 3605/8776; almost completely preserved lower jaw;

Description

The dentary occupies no more than 2/3 the entire length of the lower jaw. Its occlusal edge is equal and gently curved for its whole duration. As a result of the prolonged symphysis, occupying more than 1/4 the entire length of the lower jaw, its anterior part is elongate and concave, with shallow longitudinal furrows in its symphyseal surface that supposedly connected with a thickened mandibular covering. The low coronoid process is found at the level of the posterior third of the entire lower jaw length, and located approximately above the middle of the elongate, narrow mandibular fossa. Its dorsal external edge is formed by the surangular. The dentary process participates in the formation of the predominately anterior rear edge of the fossa. The surangular articulation of the horizontally-directed dorsal process of the dentary has a complex forked, grooved character. In the lower jaw articulation, the longitudinal convexity divides the wider medial articular area from the greatly reduced lateral one. The retroarticular process is thickened. The prearticular has a V-shaped anterior process that extends to the level of the posterior end of the occlusal edge.

Discussion

It is expedient to give a more detailed comparison between the lower jaw of caenagnathids and oviraptorids than at the species level, in order to show their similarities and differences. As has been noted, the similarity between them consists of the development of two dentary processes, the presence of large mandibular fenestrae, unique coronoid processes, and also specifically the composition of the lower jaw articulation. In this framework, there are significant differences, which have been mentioned above. Caenagnathids Oviraptorids gentle concavity along entire occlusal edge small concavity along anterior edge, which is mostly convex extensive symphysis shortened symphysis narrow, elongate mandibular fenestra wide, rounded mandibular fenestra with two posterior sections upper external edge of fenestra bounded by surangular upper external edge of fenestra bounded by dentary only adductor fossa 1/3 of lower jaw length, above middle of mandibular fenestra adductor fossa on middle of lower jaw, posterior to mandibular fenestra upper dentary ramus horizontal upper dentary ramus arches up and back anterior prearticular process beyond level of front of mandibular fenestra anterior prearticular process at rear of mandibular fenestra surangular does not divide mandibular fenestra narrow, elongate process divides mandibular fenestra mandibular fenestra displaced posteriorly mandibular fenestra displaced anteriorly

_{Source: Polyglot Paleontologist}