Small, Inflated Flexicalymene Trilobite - Ohio

This is a small specimen of the trilobite Flexicalymene retorsa from the famous trilobite beds at Mt. Orab, Ohio . It was cleaned under microscope using air abrasives to reveal the well preserved detail. It's nicely inflated and displays nicely on the small piece of shale whose base it cut flat so that it stands up on a flat surface without the need for a stand.

Flexicalymene is a genus of trilobites of the order Phacopida, suborder Calymenina. These ancient arthropods are an index fossil of the Ordovician, between 488-443 million years ago. The graceful articulation, especially of the thorax segments, demonstrates that this distant precursor of insects is deserving of its delightful name.

Flexicalymene is often found enrolled, seemingly to protect its softer underside from threats on a sea floor teeming with ancient life and increasingly complex predators. Sealing itself inside the hard carapace may be a protective maneuver, or it may simply be the pose of death.

Two species of Flexicalymene are found in the Richmond Formation of Ohio, but in different sub-units. Flexicalymene meeki has small genal spines and is the more common of the two, often coming from Mt Orab, Ohio. These spines are absent in the other species, F. retrorsa. The F. retrorsa cephalon is more rounded, while the F. meeki cephalon is pronounced. They were also denizens at different locales. Calymene, meaning “beautiful crescent”, should not be confused with Flexicalymene: it is a separate genus.

Flexicalymene meeki has been studied for its abundant perforations. The perforations have been interpreted as the loci of sensory hairs: these loci occur in many sizes, and are an interesting feature of exoskeleton microfeatures. They are concentrated on areas most likely to contact other objects in the environment.
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DETAILS
SPECIES
Flexicalymene retorsa
LOCATION
Highland County, Ohio
FORMATION
Arnheim Formation
SIZE
.6" long
SUB CATEGORY
ITEM
#40681
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