Horseshoe crabs are closely related to which group?

Horseshoe crabs are closely related to which group?

• A. Spiders
• B. Crabs
• C. Trilobites
• D. Starfish

Answer: (C)

Horseshoe crabs and trilobites highlight ancient arthropod lineages. Both belong to early euarthropods and show the segmented body plan with a hard outer exoskeleton that characterizes arthropods. Trilobites are extinct, but their fossilized bodies reveal a body design that sits near the base of the arthropod family tree, making them a natural historical relative of horseshoe crabs when thinking about deep evolutionary connections. The other options point to groups that are either not arthropods (starfish) or belong to different modern arthropod lineages (crabs as crustaceans, spiders as chelicerates) rather than these ancient, fossil-connected relatives.