Cluster of Beautiful Basseiarges Trilobites - Jorf, Morocco

This is a beautiful cluster of three Basseiarges mellishae trilobites from Jorf, Morocco. There are two dorsally preserved specimens and one ventrally preserved one with the largest being 0.8" long. The shell on these trilobites is a translucent calcite so that take on the color of the rock underneath.

Trilobites are collected from a 15-meter-thick section about 6kilometers northwest of Jorf, Morocco. Unlike many other localities, these rocks do not have distinct deposition layers, but rather are massive. They likely represent a gigantic "mud mound" that formed at the base of a volcanic island due to mud slides. The rock is very silicified, almost like a chert, and can be quite colorful. The actual shells on the trilobites are translucent: the trilobite tends to be the color of the rock it sits on.

Because the rock contains a large amount of silica, it is extremely hard, and preparing trilobites from the site is difficult since the rock does not separate well from the shell. Within the 15-meter section, only about two meters have been heavily collected, so occasionally this site will produce some extremely rare and one-of-a-kind specimens collected in float from the other layers.

A view of the collecting locality northwest of Jorf, Morocco

Collecting trilobites at the Jorf locality in 2015

About Trilobites

Trilobites are an extinct class of marine arthropods that thrived for nearly 270 million years, from the early Cambrian to the end of the Permian period (around 521 to 252 million years ago). They are one of the most successful and diverse groups in the history of life, with over 25,000 described species spanning a wide range of sizes, shapes, and ecological niches. Known for their distinctive, segmented exoskeletons, trilobites provide invaluable insights into the evolutionary history of arthropods and the dynamics of ancient marine ecosystems.