# Nipponopterus

Nipponopterus (meaning "Nippon wing") is a genus of azhdarchid pterosaur that lived during the Turonian and Coniacian ages of the Late Cretaceous period in what is now Japan. Its remains, which consist of a partial cervical (neck) vertebra, were found in the Mifune Group, located in the Kumamoto Prefecture in Kyūshū. It was made the holotype specimen of the genus and type species Nipponopterus mifunensis, named and described by paleontologist Xuanyu Zhou and colleagues in 2024. Nipponopterus represents the first pterosaur to be named from Japan.
Morphologically, Nipponopterus is similar to the pterosaur nicknamed "Burkhant azhdarchid" from Mongolia. Both are estimated to have had a wingspan measuring around 3 to 3.5 m (9 ft 10 in to 11 ft 6 in) when fully grown. In its description, Nipponopterus was assigned to the clade Quetzalcoatlinae within the family Azhdarchidae, as the sister taxon of the already mentioned "Burkhant azhdarchid".

## Discovery and naming

The holotype specimen of Nipponopterus, MDM 349, was discovered in sediments of the "Upper Formation" of the Mifune Group ('Locality 1018') in rock outcrops near Amagimi Dam in Mifune Town, Kumamoto Prefecture in Kyūshū, Japan. The specimen consists of the posterior end of the sixth cervical (neck) vertebra. The specimen was first described in 2000 as belonging to an indeterminate member of the family Azhdarchidae. The limited understanding of the clade at that time precluded more detailed analyses. While early reviews interpreted the cervical vertebra as the fourth or fifth, the most recent analysis suggests it can confidently be regarded as the sixth.
In 2024, Chinese paleontologist Xuanyu Zhou and colleagues named and described Nipponopterus mifunensis as a new genus and species of azhdarchid pterosaur based on these fossil remains. The generic name Nipponopterus combines "Nippon"—the Japanese name for the country—with "pterus", derived from the Ancient Greek word πτερόν (ptéron), meaning "wing". The specific name mifunensis refers to the type locality in the Mifune Group in Mifune Town. Nipponopterus is the first pterosaur named from Japan.
A wing phalanx and metacarpal belonging to indeterminate azhdarchid pterosaurs are also known from this formation, but have not been referred to Nipponopterus.

## Description

The holotype specimen of Nipponopterus is morphologically comparable to a similarly fragmentary unnamed pterosaur specimen from Mongolia, nicknamed the "Burkhant azhdarchid". Measurements of the material of Nipponopterus indicates that it is 82% the size of the Burkhant specimen. However, the former likely belongs to a subadult individual, meaning it was not fully grown. As such, Zhou and colleagues, in their 2024 description of Nipponopterus, estimated that both pterosaurs would have had similar wingspans, at around 3 to 3.5 m (9 ft 10 in to 11 ft 6 in).

## Classification

In their phylogenetic analysis using the dataset of paleontologist Rodrigo Pêgas in 2024, Zhou and colleagues recovered Nipponopterus as a member of the clade Quetzalcoatlinae within Azhdarchidae. It was placed as the sister taxon to the "Burkhant azhdarchid", which corroborates their close relationship in terms of similar features and geography. The results of their study are displayed in the cladogram below: