Why are horseshe crabs more similar to arachnids than crustaceans if they have four pairs of legs?

Some traits found in both horseshoe crabs and arachnids include:

- Chelicerae: These are the first pair of appendages in both groups, modified for grasping and feeding.

- Four pairs of walking legs: Although horseshoe crabs have four pairs of legs, they are not segmented as in crustaceans, but rather have a more spider-like structure.

- Open circulatory system: In contrast to crustaceans, which have a closed circulatory system, horseshoe crabs and arachnids have blood that flows freely throughout their bodies.

Despite possessing some similar characteristics, horseshoe crabs still have significant features that differentiate them from both arachnids and other crustaceans. Hence, they are considered a separate group within the Chelicerata lineage.