Sometimes referred to as feather stars or sea lilies, Crinoids are members of an extended and very ancient family of sea animals known as echinoderms. Echinoderms date back as far as the Cambrian period some 541,000,000 years ago. They include such varied animals as sea urchins, sea cucumbers, and starfish.

The evolution of crinoids was part of another explosion of complex life on Earth from the Ordovician, which resulted in most of the animal or metazoan body plans we know today. Early crinoids looked like undersea flowers, with root-like feet, a segmented columnar stalk, and feathery arms at the head which could filter and toss floating food towards the mouth.

This specimen is a crinoid fossil plate which shows the animal's fantastically intricate body structure. The soft structures at the head of a crinoid often decompose quite quickly, so fossils such as this which contain both stem and arms are quite rare.

This particular crinoid fossil is a member of the genus Mahoumacrinus and was recovered near the Erfoud region in Morocco. The fossil beds in this region are from the Devonian and date to roughly 380,000,000 years old.

Fossils are packed in a sturdy shipping box along with a certificate of authenticity and a black display stand. Each crinoid is a unique fossil and is priced by size. You can see all currently available crinoid fossils in the collection below!

While crinoids resemble plant life at first glance, they are actually animals with quite complex lifestyles. A variety of feet have been found with different species, some with root-like structures and others with curling limbs. Sprouting from this base is a long segmented stalk that ends in the crinoid's mouth and arms. These arms are covered in tiny branches that secrete sticky mucus to capture floating food particles.

Breaking down body plans into their simplest form involves looking at a concept known as symmetry. Symmetry in biology means that bodies can be divided in various ways which are more or less identical to each other.

There are three very basic forms of symmetry in biology: bi-lateral, spherical, and radial. Humans exhibit bilateral symmetry, with our bodies organized along a centerline. Spherical symmetry is generally limited to very small organisms like algae which form spherical colonies. The last form, called radial symmetry, is a bit like a pie where body parts are arranged around a central axis.

There are a number of variants to this radial symmetry wherein body parts are separated into four, five, six, or even eight symmetrical pieces. Echinoderms are the only animals that exhibit the five-part, or pentaradial form of radial symmetry. This body plan also happens to result in interesting fossil shapes.

Many crinoid species still exist to this day, with modern species surviving into adulthood without their stalks. Once their growth is complete, they detach from their segmented stems and swim through the ocean as free-floating "feather stars."

This life cycle change is thought to have become common around the Triassic period, but tracking the evolution of stem detachment is tricky. The crinoid's arms are made of soft material which can decompose quite quickly, while the endoskeleton of the stem fossilized far easier. Much of the fossil evidence of prehistoric crinoids we have today come from either these column segments or mass die-off events.

Before they were identified as fossils, segmented Crinoid stems were sometimes referred to as "fairy money". This is not so different from the way other fossils were viewed, such as "snake stones" (fossil ammonites) or "snake tongues" (fossil shark teeth).

Crinoid stems also worked their way in Christian legends in both Germany and England where they were known as St. Boniface's pfennige (pennies) and St. Cuthbert's beads. The latter is particularly interesting in the context of the Mini Museum as St. Cuthbert was a 7th-century monk on the island of Lindisfarne off the coast of Northumberland. If you'll recall, the Vikings raided this island in 793 just 100 years after the death of St. Cuthbert, for whom the monastery there is named.