1.3 Inch Carmel Colored Flexi Molt

 
 
Here is a nice mold of the Ordovician trilobite Flexicalymene retrorsa collected near Oldenburg, IN. It's above average for the species and the shell preservation is great. It is a molt, missing both free cheeks. Flexicalymene retrorsa is not seen as often as the more common Fexicalymene meeki which comes from a different member of the formation and is collected from the famous Mt. Orab locality.

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
1.31"
SUB CATEGORY
ITEM
#226
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