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Lizard fossil unearthed in west Japan found to be new species: researchers

A lower jaw fossil of a new genus and species of the Monstersauria group is seen in this photo provided by the Hyogo Prefectural Museum of Nature and Human Activities.

TAMBA, Hyogo -- A fossil unearthed from a stratum some 110 million years old in this west Japan city was part of a new lizard species, a team of scientists including those at the Hyogo Prefectural Museum of Nature and Human Activities announced on Nov. 25.

    The new genus and species of lizard discovered during 2019 excavations is believed to belong to Monstersauria, a group of varanid lizards that currently live in North America and other locations. The fossil is believed to be one of the oldest in the world for the lizard group and apparently is the first discovery of that kind in Japan.

    A reconstructed image of "Morohasaurus kamitakiensis" is seen. (Image courtesy of the Hyogo Prefectural Museum of Nature and Human Activities)

    According to the research team, the fossil is an approximately 2-centimeter part of the lower jaw, with two nearly complete 3-millimeter teeth still attached. Judging from characteristics including the long, thin jaw and the shape of the teeth, the team concluded that it belonged to the Monstersauria group. The size of the lizard is estimated to be 30-40 centimeters. The team named the species "Morohasaurus kamitakiensis" from its double-edged teeth, as such blades are called "moroha" in Japanese, and also from "Kamitaki," the name of the area where it was discovered.

    Among the Monstersauria group, there are five species belonging to one poisonous Gila monster genus across North and Central America today. Less than 20 cases of Monstersauria fossil findings have been reported worldwide, and the oldest find until now was a fossil unearthed in North America, which dates back approximately 100 million years.

    Ikeda Tadahiro, senior researcher at the Museum of Nature and Human Activities, said of the discovery, "The Monstersauria group might have moved from East Asia to North America, from where they spread. The newly found fossil will make a valuable resource in understanding the origin and evolution of the animal."

    The fossil will be placed on public display at the museum in the Hyogo Prefecture city of Sanda from Dec. 1.

    (Japanese original by Yoshiko Yukinaga, Tamba Local Bureau)

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