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| Asiatyrannus xui Zheng, Jin, Xie & Du, 2024 |
Abstract
Tyrannosaurids were the most derived group of Tyrannosauroidea and are characterized by having two body plans: gracile, long-snouted and robust, deep-snouted skulls. Both groups lived sympatrically in central Asia. Here, we report a new deep-snouted tyrannosaurid, Asiatyrannus xui gen. et sp. nov., from the Upper Cretaceous of Ganzhou City, southeastern China, which has produced the large-bodied and long-snouted Qianzhousaurus. Based on histological analysis, the holotype of Asiatyrannus xui is not a somatically mature adult, but it already passed through the most rapid growth stages. Asiatyrannus is a small to medium-sized tyrannosaurine, with a skull length of 47.5 cm and an estimated total body length of 3.5–4 m; or around half the size of Qianzhousaurus and other large-bodied tyrannosaurines in similar growth stages. Asiatyrannus and Qianzhousaurus are sympatric tyrannosaurid genera in the Maastrichtian of southeastern China. Asiatyrannus differs from Qianzhousaurus in that it has a proportionally deeper snout, longer premaxilla, deeper maxilla, and deeper dentary, and the cornual process of the lacrimal is inflated without developing a discrete horn. The different skull proportions and body sizes suggest that Asiatyrannus and Qianzhousaurus likely had different feeding strategies and occupied different ecological niches.
Keywords: Asiatyrannus xui, Tyrannosauridae, Nanxiong Formation, Upper Cretaceous, China
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Systematic paleontology
Theropoda Marsh, 1881
Tetanurae Gauthier, 1986
Coelurosauria Huene, 1914
Tyrannosauroidea Osborn, 1905
Tyrannosauridae Osborn, 1905
Tyrannosaurinae Osborn, 1905
Asiatyrannus xui gen. et sp. nov.
Diagnosis: Asiatyrannus xui is a small to medium-sized tyrannosaurine theropod that differs from other tyrannosauroids in possessing the following autapomorphies: two small, deep fossae located on the lateral surface of the premaxilla just lateral to the anteroventral border of the external naris, a large and sub-rectangular shaped maxillary fenestra, the posterior protuberances of the nasals connect to form two separated medium low ridges, a low ridge-like jugal accessory horn, the ventral margin of the anterior ramus of the jugal curving ventrally anterior to the accessory horn, the lateral surface of the descending process of the postorbital developed the anterodorsally trending fine lineations, the slender, straight, and banded-shaped postorbital bar, with almost straight and parallel anterior and posterior margins in lateral view, and the lateral surangular shelf extends to the posterior end of the surangular.
Type locality: Nanxiong Formation (Upper Cretaceous, Maastrichtian) of Shahe Town, Nankang District, Ganzhou City, Jiangxi Province, China.
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| The photograph (A) and line drawing (B) of the skull of Asiatyrannus xui (ZMNH M30360) in right lateral view. The inset box in (A) indicates the position of the detailed jugal accessory horn in (C). acf accessory fossa of maxilla; ang angular; aof antorbital fenestra; cor cornual process; d dentary; d.t dentary tooth; emf external mandibular fenestra; en external naris; f frontal; gr groove; itf infratemporal fenestra; j jugal; jah jugal accessory horn; L left; la lacrimal; mf maxillary fenestra; mnvf maxillary neurovascular foramina; mx maxilla; nas nasal; nr nasal ridge; orb orbit; par parietal; pal palatine; pmx premaxilla; po postorbital; q quadrate; qj quadratojugal; R right; sa surangular; sf surangular foramen; snf subnarial foramen; sq squamosal; t1–6 maxillary tooth 1–6. |
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| Fossil remains of Asiatyrannus xui (ZMNH M30360). (A) Skeletal outlines showing recovered elements in yellow color. The skeletal reconstruction is the proportional scaling of Lythronax argestes drawn by Scott Hartman from Loewen et al.23; (B) the skull in right lateral view; (C) the caudal vertebrae in left lateral view; (D) the right femur in posterior view; (E) the right tibia and fibula in posterior view; (F) The distal portion of the right metatarsal III in medial view and metatarsal IV in anterior view; (G) the middle shaft of the left tibia and fibula in anterior view; (H) The middle shaft of the left metatarsals in anterior view. ft the fourth trochanter; ift iliofibularis tubercle; mt metatarsal. |
Etymology: The generic name is derived from Asia, and the suffix ‘tyrannus’ is derived from the Latin word for ‘king’ or ‘tyrant’, to emphasize that this is the new tyrannosaur collected in the continent of Asia. The specific name honors Dr. Xing Xu (Institute of Vertebrate Paleontology and Paleoanthropology, Chinese Academy of Sciences), a distinguished dinosaurologist who contributed greatly to the study of dinosaurs from China, including the research of several tyrannosaurs: Guanlong, Dilong, and Yutyrannus. Dr. Xing Xu has also been a great supporter of the paleontological research and science popularization work of the Zhejiang Museum of Natural History.
Wenjie Zheng, Xingsheng Jin, Junfang Xie and Tianming Du. 2024. The first deep-snouted tyrannosaur from Upper Cretaceous Ganzhou City of southeastern China. Scientific Reports. 14, 16276. DOI: doi.org/10.1038/s41598-024-66278-5
