KOGA, Fukuoka Prefecture--A burial mound here dating to the late sixth to early seventh century has all the trappings to signify that someone important was buried at the site, with tentative evidence pointing to a connection to the Korean Peninsula.

For starters, it is keyhole shaped, a design reserved for those of the very highest rank.

Intriguingly, excavations at a burial offering pit close to the Funabaru tomb yielded remains of horse harnesses, another sign that someone who held an exulted position in life was laid to rest.

Researchers were ecstatic at the discovery of an ornament decorated with jewel beetle wings that had adorned an ancient horse harness.

Ornaments decorated with iridescent beetle wings typically are found in national treasures, such as the Tamamushi no Zushi miniature shrine housed at Horyuji temple in Nara Prefecture.

It was the first time to discover a horse tack decorated with beetle wings, which merits classification as a national treasure, the city's education board said Nov. 13.

The ornament, about 10 centimeters wide and called "gyoyo," would have hung from the waist of a horse. A space between the heart-shaped gilt-bronze open-carved plate with botanical leaf patterns and the base iron plate is lined with about 20 jewel beetle wings.

The discovery offers a fresh reminder that the area in northern Fukuoka Prefecture played a crucial role in exchanges between Japan and the Korean Peninsula in ancient times, researchers said. The gyoyo decorated with jewel beetle wings is believed to be a high-end horse trapping, more commonly associated with the Korean kingdom of Silla.

The tomb mound is about 37 meters long. A large number of grave offerings, including gilt-bronze horse harnesses, were unearthed from an offering pit near the hill of the tumulus in 2013 before it was designated by the government as a national historic site in 2016.

Horse harnesses decorated with beetle wings have been excavated from fifth-century burial mounds believed to be the resting places of the royals of Silla in what is now the South Korean city of Gyeongju.

"In Silla, horse harnesses decorated with beetle wings started to be included in tombs of senior vassals by the sixth century, but they must have been extremely valuable at the time," said Masahiro Kamiya, a former member of the Takaishi education board in Osaka Prefecture who is regarded as an expert on beetle wing ornaments found in Japan and South Korea.

Kamiya speculated that the gyoyo could have been acquired by someone skilled in diplomatic relations between the Yamato imperial court in Japan and the Korean Peninsula and in return was allowed to engage in trade.

Naoto Isahaya, an associate professor of archaeology at Kyoto Prefectural University who has made a study of horse trappings from the Korean Peninsula, said metal crafts using materials imported from Japan were prized in Silla, and that it is possible the kingdom imported jewel beetles from Japan due to the suitability of a warmer climate to allow for breeding.

"The person could have been someone who played a leading role in diplomacy with Silla that became active around that time and rapidly gained power," he said.

On the other hand, Yusuke Momosaki, a professor of archaeology at Fukuoka University, suggested the individual may have been involved in maintaining liaison between Yamato (present-day Nara Prefecture) and the Kasuya district in the northern Kyushu region.

He noted that the latter was a diplomatic outpost with post horses, citing a large ruin apparently used as a stable that was unearthed near the burial mound. Momosaki is a member of the guiding committee for research on the Funabaru site.

"It is possible that the person was responsible for swiftly relaying information concerning the Korean Peninsula to the Yamato (imperial court) and also served as a diplomat to receive emissaries from the Baekje and Silla kingdoms in the Korean Peninsula and the Sui dynasty in China and send them to Yamato," Momosaki said.

"That person might have gained possession of the horse tack decorated with beetle wings from Silla as a perk for the position," Momosaki said.

The gyoyo is on display at the city-run Koga Historical Museum in the city's Chuo district until Dec. 20.