Citrus ryukyuensis

Citrus ryukyuensis, also known as the tanibuta (Okinawan: タニブター, romanized: tanibutā, lit. 'big seed'), is a newly characterized wild citrus species native to the Ryukyus and adjacent islands, most closely related to the mainland mandarin orange, C. reticulata. As with other citrus, it is a member of the Rutaceae family. The Ryukyu and mainland species have diverged for more than 2 million years, and unlike the mainland mandarin, the Ryukyu mandarin reproduces sexually. Its hybridization with the mainland species has given rise to the unique mandarin hybrids of the islands....read more on Wikipedia.