Horseshoe crab? (Pinyin: hòu; Zhuyin: notㄡ?; scientific name: Limulidae), also known as the "horseshoe crab", "husband and wife fish", known as the living fossil. The existing horseshoe crabs only exist in three genera and four species.

Some of the species are key protection units

The Chinese horseshoe crab and the southern horseshoe crab are the key protection animals in Guangxi Province, and the Red List of Chinese Species is the endangered level.

The round-tailed horseshoe crab is a key protected animal in Guangxi Province, and the Red List of Chinese Species is a vulnerable level.