Those round shells and long legs give Japanese spider crabs an arachnid-like look, hence their common name. These animals also have spines behind and in front of their short eye stalks.

One of the many kind-of crabs -- horseshoe crabs -- is a key figure in another mystery: the Case of the Land-Living Arachnids. Horseshoe crabs first appeared in the fossil record about 450 million ...

However, recent phylogenomic studies challenge this view, indicating that horseshoe crabs are nested within the arachnids rather than forming a separate, sister lineage. This suggests that ...