What is Xiphosura?
Q: What is Xiphosura?
A: Xiphosura is an order of marine chelicerates.
Q: Which family does Xiphosura include recent species of?
A: Xiphosura includes recent species of the family Limulidae, which include the horseshoe crabs.
Q: Are the modern horseshoe crabs considered to be living fossils?
A: Yes, the modern horseshoe crabs are considered to be living fossils because they look almost identical to prehistoric genera such as the Jurassic Mesolimulus, and the group has hardly changed in millions of years.
Q: What is the traditional classification of Xiphosura?
A: Xiphosura are traditionally placed in the class Merostomata.
Q: Why is the term Merostomata considered to be paraphyletic?
A: The term Merostomata was originally made for the eurypterids, and now with the Xiphosura added, it is known to be paraphyletic.
Q: When did Xiphosura diverge from the Arachnida?
A: It is estimated that the Xiphosura diverged from the Arachnida 480 million years ago.
Q: How are the shared features of the two groups traditionally grouped in the Merostomata thought to be?
A: The shared features of the two groups traditionally grouped in the Merostomata are now thought to be retentions of primitive conditions (symplesiomorphies).
