Corythoraptor (lit.'helmeted thief') is a genus of oviraptoriddinosaur from the late MaastrichtianNanxiong Formation of South China. It contains one species, C. jacobsi, known from a single well-preserved skeleton, and named after paleontologist Louis L. Jacobs. It bears a tall crest similar to that of the modern cassowary, and possibly had a similar functionality of display and resonance to detect lower-frequency sounds.
Like other oviraptorids, the bones of Corythoraptor were heavily
niche partitioning
).
Discovery
Corythoraptor was
type specimen for the contemporary oviraptorid Heyuannia. What caused this is unclear.[1]
The name Corythoraptor is in reference to the distinct crest on its head. The species name jacobsi honors American vertebrate paleontologist Louis L. Jacobs who mentored three of the authors while they were getting their PhD's at Southern Methodist University, Dallas, Texas.[1]
Description
Skull
Skull reconstruction (left) and head restoration (right)
Corythoraptor bore a tall crest on its head similar to that of the modern cassowary, with a 2 mm (0.079 in) thick perhaps keratinous bony shell casing. The crest is pneumatized and features several chambers separated by thin bony walls, though the crest of Corythoraptor is more pneumatized than that of the cassowary. This may have made the crest quite pliable, incapable of withstanding concussive force such as during head butting.[1]
Corythoraptor had a relatively large
ornithomimids. The ventral side (underside) of the premaxillae is highly broken up, which could indicate the bone was lightweight, perhaps being pneumatized. Corythoraptor was toothless.[1]
Postcranial skeleton
Holotype block
Line diagram of the block
Corythoraptor has 12
neck vertebrae. The 6th and 11th vertebrae are the longest. There is a pleurocoel (an air pocket) on the 5th through 12th vertebrae located on the middle of each vertebra. The pleurocoel is nearly circular on the 5th vertebra, diameter 4.8 mm (0.19 in), and ovular on the 6th, length 5 mm (0.20 in). The articular surface (where a vertebra contacts another vertebra) on the anterior (headward) side is strongly concave, and the posterior (tailward) articular surface is moderately convex. The anterior articular surfaces are almost square and are wider than the posterior articular surfaces. The ribs are fused to the vertebrae. The neural arches (which project outwards from the vertebrae) are densely pneumatized with several small air chambers.[1]
It is unclear how many
prezygapophysis (which locks two vertebrae together) and the transverse process (which juts out diagonally from the vertebra); the infradiapophyseal fossa at the base of the transverse process; and the pleurocoel. The neural arches are similar to those of Nankangia.[1]
phalanges (finger bones) are long and robust, the longest being the first phalanx about 72% longer than the second metacarpal, and the third phalanx is the smallest. The unguals (claws) are weakly curved, and decrease in size and curvature from first to third finger.[1]
Corythoraptor, being a
theropods, the phalangeal formula (the number of phalanges per digit) is 2-3-4-5. The 3rd digit is the longest, and the 4th is slightly longer than the 2nd. The toe claws are moderately curved.[1]
Classification
Corythoraptor is an
Zamyn Khondt oviraptorid, Rinchenia, and Oviraptor. There was a high oviraptorid diversity in the Late Cretaceous of South China, with representatives of three different oviraptorid clades. Below is a family tree of Oviraptoridae based on Lü et al., 2017 (bolded species inhabited South China):[1]
The validity of Corythoraptor was called into question by Cau (2024), who considered it to be a
ontogenetically variable characters. As such, Corythoraptor would represent a more mature individual of Banji.[2]
Paleobiology
Diet
The jaw structure of oviraptorids is similar to those of herbivorous
xerophytic (drought-resistant) plants as oviraptorids are typically found in arid environments, as well as nuts and seeds. It has also been proposed they ate shellfish, but the jaws do not appear to have been well-equipped to crush shells, and the arid environment probably did not sustain a high enough shellfish population.[3]
Because six different oviraptorid species are known from Ganzhou, they may have exhibited
niche partitioning, with different species targeting different foods.[1]
Ontogeny
Comparison between the casque of Corythoraptor and the southern and northern cassowaries
Based on
histological analysis on a portion of the fibula and radius, the growth marks indicate the holotype was older than 6 or 7 years when it died. A portion of the radius bears 3 distinct dark bands which indicate periods of arrested growth, which points to seasonal growth spurts. Because growth restarted near the edge of the bone, the specimen probably died at the beginning of a new growing season and therefore was still a young adult which had not yet reached its maximum size. If the crest did serve as a mating display, this would suggest Corythoraptor was sexually active before it finished growing, and that growth continued for more than 8 years. At this point in its development, Corythoraptor reached about 1.6 m (5 ft 3 in) in length, which is medium-sized for an oviraptorid.[1]
Function of crest
The crest of Corythoraptor is apparently quite similar to the casque of the modern cassowary. The cassowary uses its casque to dissipate heat from the brain cavity, and as an resonator to aid in the detection or gauge the point of origin of low frequency signals across a greater distance. In Corythoraptor, the latter may have been used to hear predators or prey items, or possibly to pick up low frequency mating calls as modern cassowaries do. However, it is unclear if Corythoraptor was capable of producing low frequencies since these are produced in the throat. It is also possible the crests were used for display, with larger and more ornamented casques equating to higher ranking in the group hierarchy or better fitness during mating season, but cassowary casques do not vary very much between individuals. The cassowary-like crest, neck, and sharp claw may indicate Corythoraptor had a cassowary-like lifestyle.[1]
Paleoenvironment
Group of Corythoraptor in the Late Cretaceous settings of the Nanxiong Formation
Ganzhou is well renowned for its oviraptorid diversity, yielding oviraptorid egg clutches, skeletons, and six other genera:
