【画像】上下に歯が二重に並んでいる頭蓋骨
画像はイメージ（Flicker/ Anselm Hook ）
〈歯が二重に並んでいる頭蓋骨が、注目されています〉
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This is what our skull looks like before we lose all our Primary teeth which are shed and replaced by permanent teeth. The first primary tooth comes in at about 6 months of age and the 20th and last primary tooth erupts at around 2 1/2 years of age. pic.twitter.com/Rd57gDRSvb
— Howard Farran (@HowardFarran) January 4, 2019
