A creature X, is considered to be currency of the people of an island that sunk into the ocean. The holes on its body are also considered to symbolise the wounds of a Godly figure (his birthday happens to be today) who was crucified. These creatures have quite a peculiar way of eating, and use their spines to consume food.
sand dollar (sea urchins)
Sand dollar, coins left by Dead Mermaids, supposed currency of mythical island of Atlantis.
The correct answer is sand dollar, a type of sea urchin. The holes on their body are said to symbolise Christ (birthday 25 December).