''Casterolimulus'' is an extinct genus of

xiphosuran Xiphosura (; , in reference to its sword-like telson) is an order of arthropods related to arachnids. They are more commonly known as horseshoe crabs (a name applied more specifically to the only extant family, Limulidae). They first appeared in t ...

. It is known from the Late Cretaceous

Fox Hills Formation The Fox Hills Formation is a Cretaceous geologic formation in the northwestern Great Plains of North America. It is present from Alberta on the north to Colorado in the south. Fossil remains of dinosaurs, including tyrannosaurs, as well as lar ...

of North America, and is believed to have lived in freshwater environments. It belongs to the family

Limulidae Horseshoe crabs are arthropods of the family Limulidae and the only surviving xiphosurans. Despite their name, they are not true crabs or even crustaceans; they are chelicerates, more closely related to arachnids like spiders, ticks, and scorpi ...

, and is considered a close relative of ''

Victalimulus ''Victalimulus mcqueeni'' is an extinct horseshoe crab, from Early Cretaceous (Aptian) Koonwarra Fossil Beds in eastern Victoria, Australia. The holotype and only known specimen was discovered by James McQueen who was encouraged by Leon Costerma ...

,'' which is from the Early Cretaceous of Australia.

References

Xiphosura {{Paleo-arthropod-stub