Nurhachius


Nurhachius is a genus of istiodactylid pterodactyloid pterosaur from the Barremian-Aptian-age Lower Cretaceous Jiufotang Formation of Chaoyang, Liaoning, China.

Discovery

The genus was named in 2005 by Wang Xiaolin, Alexander Kellner, Zhou Zhonghe and Diogenes de Almeida Campos. The type species is Nurhachius ignaciobritoi. The genus name refers to Nurhaci, the first emperor of the Qing Dynasty, whose original power base encompassed the region where the fossil was found. The specific name honours the late Brazilian paleontologist Ignácio Aureliano Machado Brito, who pioneered the study of pterosaurs in his country.
Nurhachius was first described based on its holotype fossil, IVPP V-13288, a partial skull and skeleton. A second specimen, IVPP V-13288, was later referred to the species.
In 2019, a second species was named: Nurhachius luei. The specific name honours the late Lü Junchang. It is based on the holotype BPMC-0204 from the lower Jiufotang Foramation, a skull with lower jaws and seven neck vertebrae.

Description

The wingspan of Nurhachius was estimated at 2.4-2.5 m. In 2008, Witton estimated the span at 228 centimetres, the weight at four kilogrammes.
In 2019, a single apomorphy, or unique distinguishing trait of the genus as such, was indicated: the front tip of the palate is slightly turned upwards.
The skull is elongated with in the holotype a preserved length of 315 millimetres and an estimated total length of about 330 millimetres. The nasoantorbital fenestra, the large skull opening, is relatively long at 58% of the skull length. The lower jaws have a length of 291 millimetres. The skull is similar to that of Istiodactylus, which lived at about the same time in what is now England, especially in the teeth that are compressed side to side and the long fenestra. However, it differs from Istiodactylus in several details, including a significantly lower skull, different jugal and a slight curve to the upper margin of the lower jaw. The teeth are curved to the back, have three roots and are robust. They are limited to the anterior ends of the jaws; there are 28 teeth in the upper jaws and 26 in the lower jaws for a total of 54. Most elements of the postcranial skeleton are known, with the exception of some cervical vertebrae, the ribs, the tail and the two most extreme phalanges of the wing finger.

Classification

The describers pointed out several similarities with the Pteranodontoidea and one, the warped deltopectoral crest of the humerus, unique to just the clade Istiodactylus + Anhangueridae. A cladistic analysis performed by Wang and colleagues showed that Nurhachius was a member of the Istiodactylidae. Its position as being closely related to Istiodactylus was supported by a 2008 analysis by Lü Junchang.
In 2008 Lü also suggested that Nurhachius was a junior synonym of another istiodactylid from the same ecosystem, Liaoxipterus. However, a 2012 analysis by Mark Witton found that these two istiodactylids were not identical and, more importantly, did not group together in a phylogenetic tree. Witton also noted that they did not actually group together in Lü's study either.
In 2019, the membership of the Istiodactylidae was confirmed. Nurhachius was recovered above Hongshanopterus and below Liaoxipterus in the evolutionary tree. Nurhachius ignaciobritoi and Nurhachius luei were sister species.
Below is a cladogram showing the phylogenetic placement of this genus within Pteranodontia from Andres and Myers.
The cladogram below is a topology recovered by Kellner et al.. In the analyses, they recovered Nurhachius as the sister taxon of the subfamily Istiodactylinae within the family Istiodactylidae, and placed within the more inclusive group Istiodactyliformes.