Synziphosurina is a paraphyletic group of chelicerate arthropods previously thought to be basal horseshoe crabs (Xiphosura).

[3] While Weinbergina and Willwerathia being exceptionally large,[8] most synziphosurines are small arthropods with body length ranging only about a few centimeters long.

[9] The body of synziphosurine composed of a prosoma covered by a dome-like carapace (prosomal dorsal shield) and an opisthosoma with usually unfused 9-11 segments expressed by tergites.

[11][3] Evidences of appendages are scarce, fragmentary known from Anderella parva,[12] Camanchia grovensis[13] and Venustulus waukeshaensis[14] while exceptionally well-documented in Weinbergina opitzi.

[3] The even basal euchelicerates Offacolus and Dibasterium, the questionable genus Borchgrevinkium, as well as the Dekatriata-related Houia and Winneshiekia, may also regarded as members of synziphosurines in some literatures.