MUKAWA, Hokkaido – Fossils found here appear to be of an unknown dinosaur species that was the ancestor of birds, the University of Hokkaido and the city of Mukawa on January 6th.
The fossil fragments of rib bones, hind legs, pelvis and other body parts were excavated from the stratum of the later stages of the Cretaceous Period (100 million years to 72 million years ago).
The fossil collector Yoshiyuki Horita, a resident of Mukawa, discovered the riverside in the Hobetsu district of the city around 1990. Horita brought the fossils to the government-run Hobetsu Museum home.
Museum staff began cleaning the fossils in June last year and noticed the unfamiliar shape.
The museum asked Yoshitsugu Kobayashi, professor of vertebrate paleontology at Hokkaido University, to study the fossils. He said what remains is likely to be the remains of a theropod, a bipedal group from which birds are believed to have originated.
The fossils were excavated from the same stratum where a dinosaur-filled skeleton was found in 2013. The dinosaur, named Mukawa-ryu, was identified as a new species and received the scientific name Kamuysaurus japonicus in 2019.
The recently discovered teropod was living in an earlier time than that Mukawa-ryu.
“The latest discovery is as remarkable as the Mukawa-ryu discovery,” said Kobayashi, who has led Kamuysaurus research. “Maybe we can solve the mechanism of macroevolution (from dinosaurs to birds).”