The Machikane Crocodile fossil on display at the Museum of Osaka University, Toyonaka City, Osaka Prefecture.
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More than 60 years ago, Japan's first complete crocodilian skeleton fossil, the Machikane Crocodile, was discovered. In June 2025, the Agency for Cultural Affairs recommended that it be designated a Natural Monument, with formal recognition expected this fall.
Named after the Machikaneyama district in Toyonaka, Osaka Prefecture, where it was unearthed during construction work on the University of Osaka's Toyonaka campus, the fossil has long been cherished by residents. University officials expressed their delight, saying they hope the designation will provide an opportunity to draw global attention.
A Fossil Beyond Imagination
The Machikane Crocodile fossil on display at the University of Osaka stuns with its scale. A skull more than a meter long and a body stretching some seven meters, far larger than anything one might imagine prowling prehistoric Japan.
Associate Professor Ken Ito, who oversees the collection, notes the discovery dates back to May 1964. Two young fossil enthusiasts unearthed fragments at a campus construction site and delivered them to the Museum of Osaka University.
Initially mistaken for cattle bones, further excavation uncovered a massive skull, confirming the find as a crocodile. Dated to around 450,000 years ago, the skeleton was almost entirely intact, an extraordinary stroke of preservation and a landmark discovery for Japanese paleontology.
Life Remains a Mystery
Research on the fossil and surrounding geology has revealed some features of the Machikane Crocodile.
It is estimated to have been about seven meters in length, weighing around 1.3 tons. Unlike modern crocodiles, which live mainly in tropical and subtropical regions, this species adapted to temperate climates and likely inhabited shallow waters.
Its teeth exhibited unique traits compared to those of other crocodiles. Evidence of injuries, broken bones, and puncture-like bites suggested encounters with other crocodiles and possible natural breeding populations. In recent years, some scholars have even proposed that close relatives of the Machikane Crocodile inspired ancient dragon legends.
Yet many details about its life remain unknown, and research is ongoing. "If you are studying crocodiles of that era, the Machikane Crocodile is indispensable," Ito emphasized, calling it a globally significant specimen.
From Fossil to Mascot
Over time, the Machikane Crocodile has become part of local identity. The University of Osaka created Dr Wani as its official mascot, while Toyonaka City adopted Machikane-kun, a crocodile mascot introduced during its 50th anniversary celebrations.
According to Toyonaka City, the upcoming Natural Monument designation will be the first within the city and the first in Osaka Prefecture in 69 years, raising expectations for renewed attention.
"The Machikane Crocodile still holds many mysteries," Ito said. "I hope more researchers will take an interest and help uncover its secrets."
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Author: Saki Maehara, The Sankei Shimbun
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