Yutyrannus

Article

August 19, 2022

Yutyrannus is a genus of prokeratosaurid tyrannosauroid dinosaur from the Early Cretaceous of China. Its type species is called Yutyrannus huali. The species was described based on three nearly complete specimens, two adults and one juvenile, recovered from the Yixian Formation in Liaoning Province. Yutyrannus was a large bipedal predator. The holotype was about 9 meters long and had an estimated weight of 1,400 kg. The skull of the holotype was about 90 centimeters and weighed about 600 grams, the one of the paratype measured 63 centimeters and weighed about 500 grams. This genus was especially important to paleontology because evidence of fossilized feathers was found which may suggest that other tyrannosauroids could have adult plumage. Since 2004, the discovery of the genus Dilong raised the possibility that tyrannosauroids had a thin plumage, in the 1st stage, in at least some stage of development. The new findings on Yutyrannus suggest that the plumage may have covered the members of this family throughout their lives, as well as the raptors. define if they were a single filament or if it had branches. The plumage of the 1st stage, existing in Dilong, was filamentous, similar to that existing in chicks (Gallus gallus), resembling a fur rather than a feather. In Yutyrannus, this plumage could reach 20 centimeters in length, giving the animal a similar appearance to a mammal.

Discovery

Yutyrannus huali was scientifically named and described in 2012 by Xu Xing et al. The name is derived from Mandarin Chinese yǔ (羽, "feather") and Latinized Greek tyrannos (τύραννος, "tyrant"), a reference to its classification as a feathered member of the superfamily Tyrannosauroidea. The specific name consists of the Mandarin Huáli (simplified 华丽, traditional 華麗, "beautiful"), in reference to the perceived beauty of its possible plumage. Yutyrannus is known from three nearly complete fossil specimens (an adult, an adolescent, and a juvenile) acquired from a fossil dealer who claimed that all three came from a single quarry in Batu Yingzi, Liaoning Province, China. They were therefore likely found in a layer of the Yixian Formation, dating to the Aptian, approximately 125 million years old. The specimens were cut into bath mat-sized pieces that could be carried by two people. The holotype, ZCDM V5000, is the largest specimen, consisting of an almost complete skeleton with skull, compressed into a slab, of an adult individual. . The paratypes are the other two specimens: ZCDM V5001 consisting of a skeleton of a smaller individual and part of the same plate as the holotype; and ELDM V1001, a juvenile estimated to be eight years younger than the holotype. The fossils are part of the collections of the Zhucheng Dinosaur Museum and the Erlianhaote Dinosaur Museum, but were prepared by the Institute of Vertebrate Paleontology and Paleoanthropology under Xu's guidance.

Description

Yutyrannus was a large bipedal predator. The holotype and oldest known specimen has an estimated length of 9 meters and an estimated weight of around 1,414 kg. In 2016, Gregory S. Paul gave lower estimates of 7.5 meters and 1.1 tons. Its skull has an estimated length of 905 millimeters. The skulls of the paratypes are 80 centimeters and 63 centimeters long and their weights have been estimated at 596 kg and 493 kg, respectively. The descriptors have established some diagnostic traits of Yutyrannus, in which it differs from its direct relatives. The snout has a high ridge in the midline, formed by the nasals and premaxillae and which is covered by large recesses.