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 sit in an ancient arthropod lineage, and trilobites are iconic early members of the same broad evolutionary path that helps us understand how these tough-bodied arthropods first diversified. Both share features that reflect that early body plan—like a hard exoskeleton and segmented body—looking back to a common ancestral design. In this framing, trilobites represent that deep, ancestral arthropod connection, which is why they’re the best fit among the options. The other groups—spiders (modern arachnids), true crabs (crustaceans), and starfish (echinoderms)—come from different lineages and are not as closely tied to the horseshoe-crab lineage in the context of ancient arthropod evolution.

Horseshoe crabs sit in an ancient arthropod lineage, and trilobites are iconic early members of the same broad evolutionary path that helps us understand how these tough-bodied arthropods first diversified. Both share features that reflect that early body plan—like a hard exoskeleton and segmented body—looking back to a common ancestral design. In this framing, trilobites represent that deep, ancestral arthropod connection, which is why they’re the best fit among the options. The other groups—spiders (modern arachnids), true crabs (crustaceans), and starfish (echinoderms)—come from different lineages and are not as closely tied to the horseshoe-crab lineage in the context of ancient arthropod evolution.