Urokodia

The dorsal exoskeleton (tergite) compose of a cephalon (head) and a pygidium (tail shield) of subequal size.

However, subsequent studies revealed the pygidium had distinct triangular shape and a parallel row of tiny posterior spikes.

[3] The ventral appendages of Urokodia had been unknown for a long time, and its dorsal features resemble Mollisoniidae (e.g. Mollisonia, Thelxiope, and Corcorania) at first glance.

[4] However, a redescription published in July 2024 discovered the appendages of Urokodia unlike those of a mollisoniid or any other chelicerates.

Phylogenetic analysis based on the new discovery instead placing Urokodia as the most basal member of Artiopoda, an extinct group which include trilobites and their relatives.

Recent (A) and previous (B) reconstructions