Seahorses are a unique type of marine fish in that male seahorses have pouches that allow them to incubate and raise young fish, while female seahorses do not have pouches. This phenomenon of gender role reversal is very rare in the animal kingdom and has attracted widespread attention and research...
Life originated in the primitive ocean, and the earliest vertebrates were also born in the waters. Both armored fish and placoderm fish once flourished in Earth's waters, but they soon withdrew from the stage of history. There are many factors that contributed to their extinction, but the mai...