About
As you proceed along National Route 299, which winds through the mountains of Kanna Town in Gunma Prefecture, a rock wall called Serin no Rengan (Ripple Marks of Serin) appears, standing 15 meters high and 11 meters wide. Engraved on the surface of this rock are traces of waves formed during the Cretaceous period, about 120 million years ago. At that time, this place was under the sea, and the waves crashing onto the sandy beach created patterns in the sand, which eventually fossilized over the ages. These ripple marks were designated as a natural monument of Gunma Prefecture in 1965 (Showa 40).
However, an even more astonishing secret was hidden in this rock wall. In 1985 (Showa 60), researchers discovered that the depressions on the upper part of the ripple marks were actually dinosaur footprints. This was the first confirmed fossilized dinosaur footprint in Japan, and the then Nakazato Village (now Kanna Town) went on to declare itself the "Dinosaur Kingdom." On the upper left part of the rock wall are two footprints of a large bipedal dinosaur, and from the upper right to the lower left are a series of smaller dinosaur tracks. These footprints are clear evidence that dinosaurs once walked this land.
These strata belong to a mountainous graben belt running along National Route 299 from Ogano Town in Saitama Prefecture, across the Shigasaka Pass, through Kanna Town and Ueno Village in Gunma Prefecture, over the Jukkoku Pass at the Gunma–Nagano border, and finally reaching Sakuho Town in Nagano Prefecture—a stretch about 40 kilometers long and 2–4 kilometers wide. This graben belt is a region where the early Cretaceous strata are widely exposed, and many dinosaur footprints and fossils have been discovered here.
Near the Serin no Rengan, the Kanna Town Dinosaur Center exhibits dinosaur fossils and models. Events such as fossil excavation experiences are also held, allowing visitors to feel the romance of ancient times. A visit to this area will surely allow you to experience the breath of dinosaurs from over 100 million years ago.
群馬縣神流町境內，國道299號線穿越群山，途中會出現一面稱為瀬林的漣痕（又稱「漣痕岩」）的岩壁，高15公尺、寬11公尺。這塊岩壁上刻有約1億2千萬年前白堊紀時期形成的波浪痕跡。當時，這裡曾是一片海洋，海浪拍打著沙灘，在沙面上留下了紋理，隨著歲月流逝化石化，成就了現在所見的漣痕。這些漣痕於昭和40年（1965年）被指定為群馬縣的天然紀念物。
然而，這塊岩壁中還隱藏著更令人驚奇的發現。昭和60年（1985年），研究人員在漣痕的上方發現了恐龍足跡的窪陷，這是日本首次確認的恐龍足跡化石。當時的中里村（現已合併為神流町）也因此宣稱成為「恐龍王國」。岩壁的左上部有兩個大型二足步行恐龍的足跡，從右上到左下還連綿著小型恐龍的足跡。這些化石足跡正是恐龍曾經在這片土地上行走的證據。
這一地層屬於一條沿著國道299號線，從埼玉縣小鹿野町經志賀坂隘口，穿越群馬縣神流町、上野村，再橫跨上信國境的十石隘口，直抵長野縣佐久穗町的全長約40公里、寬度2至4公里的山間地溝帶。這一地溝帶廣泛分布著白堊紀前期的地層，是恐龍足跡和化石多有出土的重要區域。
在瀬林漣痕附近，設有神流町恐龍中心，館內展出各式恐龍化石與模型，並舉辦化石挖掘體驗等活動，讓來訪的遊客都能感受到遠古時代的浪漫與奇趣。造訪這片土地，彷若可以親身感受億萬年前恐龍呼吸奔馳於此的氣息。