Monday, July 31, 2017

[Paleontology • 2017] Corythoraptor jacobsi • High Diversity of the Ganzhou Oviraptorid Fauna Increased by A New “Cassowary-like” Crested Species


Corythoraptor jacobsi
Lü, Li, Kundrát, Lee, Sun, Kobayashi, Shen, Teng & Liu, 2017


Abstract
A new oviraptorid dinosaur from the Late Cretaceous of Ganzhou, bringing oviraptrotid diversity of this region to seven taxa, is described. It is characterized by a distinct cassowary-like crest on the skull, no pleurocoels on the centra from the second through fourth cervical vertebrae, a neck twice as long as the dorsal vertebral column and slightly longer than the forelimb (including the manus). Phylogenetic analysis recovers the new oviraptorid taxonCorythoraptor jacobsi, as closely related to Huanansaurus from Ganzhou. Osteochronology suggests that the type specimen of Corythoraptor had not reached stationary growth stage but died while decreasing growth rates. The histology implies that it would correspond to an immature individual approximately eight years old. We hypothesize, based on the inner structure compared to that in modern cassowaries, that the prominent casque of Corythoraptor was a multifunction-structure utilized in display, communication and probably expression of the fitness during mating seasons.

Figure 1: The holotype of Corythoraptor jacobsi gen. et sp. nov. (JPM-2015-001). (a) Photograph. (b) Outline drawings. (c) Close up of the skull and lower jaw, showing the pneumatic cassowary-like crest (Only skull and lower jaw elements are labeled). (d) Skeletal reconstruction (missing parts are in grey).

 Abbreviations: aof, antorbital fenestra; cav. caudal vertebrae; cr. cervical ribs; cv. cervical vertebrae; dv. dorsal vertebrae; fe, femur; fi. fibula; h, humerus; il, ilium; is, ischium; l, lacrimal; lj, lower jaw; ltf, lower temporal fenestra; m, maxilla; n, nasal; nar, narial opening; o, orbit; oc, occipital condyle; p, parietal; pm, premaxilla; po, postorbital; ps, pes; psc, pneumatic skull crest; pu. pubis; q, quadrate; ra, radius; sk, skull; sq, squamosal; stf, super temporal fenestra; ti, tibia; ul, ulna. Scale bar = 8 cm in (c) and 100 cm in (d).




Systematic palaeontology

Oviraptorosauria Barsbold, 1976.
Oviraptoridae Barsbold, 1976.

Corythoraptor jacobsi gen. et sp. nov.

Etymology: The generic name Corythoraptor refers to a raptor bearing a “cassowary-like crest” on its head, and the specific name is in honor of Professor Louis L. Jacobs, who has contributed to dinosaur research and has given excellent mentoring to three authors (JLü, YL and YK) when they were Ph.D. students at Southern Methodist University, Dallas, Texas, USA.

Type locality and horizon: A site in the vicinity of the Ganzhou Railway Station (GPS coordinates are provided on request from the first author), Ganzhou City; Campanian-Maastrichtian; Nanxiong Formation (Upper Cretaceous).

 Diagnosis: An oviraptorosaurian dinosaur with the following unique combination of characters: ratio of the length of the tomial margin of the premaxilla to the premaxilla height (ventral to the external naris) is 1.0–1.4; inclination of the anteroventral margin of the premaxilla relative to the horizontally positioned ventral margin of the jugal posterodorsal; antorbital fossa bordered anteriorly by the maxilla; narial opening much longer than width; infratemporal fenestra dorsoventrally elongate, narrow anteroposteriorly; the supranarial process of the premaxilla bears two processes: a short posterodorsally extending process, forming the anterodorsal margin of the external nasal opening, and a long process, forming most of the anterodorsal process of the premaxilla; distinct cassowary-like helmet on the skull; long axis of the external narial opening parallel to the dorsal margin of antorbital fenestra; straight anterodorsal margin of dentary in lateral view; a deep fossa, sometimes with associated pneumatopore on lateral surface of dentary; no pleurocoels on the centra from the second through fourth cervical vertebrae; the length of the neck twice as long as the dorsal vertebral column, and slightly longer than the entire forelimb length (including the manus); less pronounced deltopectoral crest of humerus, forming an arc rather than being quadrangular; ratio of the length of the manus to the length of the humerus plus the radius between 0.50 and 0.65; the ungual of digit III less curved than other unguals; lesser trochanter (cranial trochanter) completely fused with the greater trochanter and distal ends of shafts of metatarsal II straight and metatarsal IV laterally deflected. 

Corythoraptor jacobsi gen. et sp. nov. is assigned to oviraptorid dinosaurs based on the following characters: proximal caudals with pneumatized centra; ischium with its posterior profile concave3; premaxilla pneumatized; the subantorbital portion of the maxilla inset medially; the palate extending below the cheek margin; the external naris overlapping most of the antorbital fossa rostrodorsally; the bones of the skull roof pneumatized; the pubic shaft concave cranially, the mandibular symphysis tightly sutured; the shortened preorbital region, and the toothless jaws.

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Figure 2: The cranial casque of Corythoraptor jacobsi and recent cassowaries. (a–c) the crested skull of Corythoraptor and head appearance restorations. (d) a close-up (see dotted rectangle in a and b) of eroded bony shell in the posterolateral casque of Corythoraptor. (e) the crested skull of the recent cassowary (Casuarius uniappendiculatus; Museum für Naturkunde in Berlin, Germany: MfN-ZMB 93274). (f) a keratinous helmet over the skull of the recent cassowary (unnumbered specimen of Casuarius casuarius from the osteological collections of ZOO Protivín, Czech Republic). (g,h) coronal cuts through the cassowary skull – (g) Casuarius casuarius MfN-ZMB 36820, (h) Casuarius casuarius: MfN-ZMB 36885 (see dotted lines in f); note transition in strut-like trabecular arrangement. (i) close-up to contact between keratinous and skeletal components of the casque in recent cassowary, unnumbered specimen of Casuarius sp. from the osteological collections of Field Museum of Natural History, Chicago, USA.

Abbreviations: cq, casque; cr, cranium; exs, external surface; kesh, keratinous sheath; or, orbit; tr, trabeculae.

Figure 5: The living scene of Corythoraptor jacobsi gen. et sp. nov.
Drawn by Zhao Chuang


 

Junchang Lü, Guoqing Li, Martin Kundrát, Yuong-Nam Lee, Zhenyuan Sun, Yoshitsugu Kobayashi, Caizhi Shen, Fangfang Teng and Hanfeng Liu. 2017. High Diversity of the Ganzhou Oviraptorid Fauna Increased by A New “Cassowary-like” Crested Species.
  Scientific Reports. 7, Article number: 6393. DOI: 10.1038/s41598-017-05016-6


Introducing Corythoraptor jacobsi.  paleonerdish.wordpress.com/2017/07/28/introducing-corythoraptor-jacobsi/ via @ferwen


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