Inch Long Flexicalymene Trilobite Molt

 
Here is a molted Flexicalymene trilobite just over an inch long from Indiana. Like modern day lobsters and many types of insects, trilobites molted during their lifetime leaving the old shell behind. You can tell a molt because it's missing the "free" cheeks on the side of it's head that detached as it discarded it's old shell.

Flexicalymene is a genus of trilobites of the order Phacopida, suborder Calymenina. These ancient arthropods are an index fossil of the Ordovician (488-443 mya). 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.

There are two species of Flexicalymene found in the Richmond Formation but in different sub-units. Flexicalymene meeki have small genal spines and is the more common of the two, often coming from Mt Orab, Ohio. These spines are absent in 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 those areas likely to contact other objects in the environment.
DETAILS
SPECIES
Flexicalymene retrorsa
LOCATION
Oldenburg, Indiana
FORMATION
Richmond Formation
SIZE
1.05" long
SUB CATEGORY
ITEM
#281
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