These two figures show the holotype (and only known specimen) of the Lower Cambrian echinoderm Helicoplacus guthi. (The lower case g is standard for species names, and the ending i makes it Latin possessive). As noted in Durham (1993, p.601), the species name honors the collector.

Note the spiraling (helically) rows of plates radiating from the base, which in life probably was anchored in the muddy substrate.

The fossil comes from the Lower Cambrian Poleta Formation of eastern California.

Perhaps ironically, H. guthi is not a trilobite. As an echinoderm its relatives include the star fish, sea lily, and sea cucumber.

Last revision 10/18/2015