Xiphosura (/zɪfoʊˈsjʊərə/; from Ancient Greek ξίφος (xíphos) 'sword' and οὐρά (ourá) 'tail', in reference to its sword-like telson) is an order of arthropods...

during development A = Antenna L = Leg C = Chelicera P = Pedipalp Ci = Chilarium Mnd = Mandible Mx = Maxilla The Chelicerata are arthropods as they have:...

during development A = Antenna L = Leg C = Chelicera P = Pedipalp Ci = Chilarium Mnd = Mandible Mx = Maxilla The (pan)arthropod head problem is a long-standing...