蝌蚪文字 is considered a type of ancient Chinese seal script.
The standard modern word for tadpole; 蝌蚪 is a rare literary synonym.
ancient seal-script character; tadpole script character
Literary or classical kanji form for tadpole; rarely used in modern Japanese.
Alternate kanji form, also rare and mostly found in historical or seal-script contexts.
From Chinese 蝌蚪 (kēdǒu), literally 'tadpole'. The character shape sense derives from the resemblance of the ancient script to tadpoles.