Xiphosura facts for kids
Quick facts for kids XiphosuraTemporal range: Silurian – Recent
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| Horseshoe crab (Limulus polyphemus) | |
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Xiphosura
Latreille, 1802
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Xiphosura is a group of amazing sea creatures. It's a special group of chelicerates that live in the ocean. This group includes many types of animals that are now extinct. But there are still four living species left today. These living species are the famous horseshoe crabs. They belong to a family called Limulidae.
These ancient animals have barely changed over millions of years. Modern horseshoe crabs look almost exactly like their ancestors from the Jurassic period. For example, the prehistoric Mesolimulus looked very similar. Because they have changed so little, horseshoe crabs are often called living fossils. It's like looking at a creature from millions of years ago!
What are Xiphosura?
Scientists used to place Xiphosura in a larger group called Merostomata. This name was first used for another ancient group, the eurypterids (also known as sea scorpions). Later, Xiphosura were added to Merostomata. However, scientists now know that Merostomata is not a "natural" group. This means it doesn't include all the descendants from a single ancestor.
Even though you might still see the name Merostomata in some books, scientists prefer to use more accurate terms. The features that Xiphosura and eurypterids share are thought to be very old traits. They are not unique features that show a close relationship between just these two groups.
Family Tree of Xiphosura
The Xiphosura group is very old in the animal family tree. They are like an early branch that split off. Scientists believe that Xiphosura are closely related to two other groups: the Eurypterida (sea scorpions) and the Arachnida (spiders, scorpions, and ticks).
It's thought that Xiphosura separated from the Arachnida group a very long time ago. This split happened about 480 million years ago. This shows just how ancient and unique these horseshoe crabs truly are!
Images for kids
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Mesolimulus from the Solnhofen limestone
See also
In Spanish: Xifosuros para niños
