Gravicalymene  abbreviata


Gravicalymene abbreviata (Foerste, 1910) is a distinctively granulose calymenid trilobite commonly found in fossiliferous limestones and shales of the lower Cincinnatian Series of southwestern Ohio, southeastern Indiana, and northern Kentucky, USA


It is frequently misidentified as the nominal species Flexicalymene granulosa, even by professional trilobitologists.


Gravicalymene abbreviata is reminiscent of a granulose Flexicalymene, but several consistent characters indicate assignment to a calymenid genus other than Flexicalymene.  The specimen below is a complete Gravicalymene abbreviata from shales of the Kope Formation in southern Brown County, Ohio.


Gravicalymene abbreviata (3.8 cm long) from the Kope Formation (Edenian Stage, lower Cincinnatian Series, Upper Ordovician) of southern Brown County, Ohio, USA.  Specimen collected by Mark Peter.



This species differs from species assigned to Flexicalymene in subtle, but meaningful, ways:


1) bell-shaped glabella (vs. a tapering forward glabella with sublinear border furrows in Flexicalymene)


2) relatively wider (tr.) thoracic axial lobe


3) different configuration of lateral glabellar furrows (especially the S1 furrows, which are directed anterolaterally; in Flexicalymene, they are strongly directed laterally, but bowed forward (convex anteriorly))


4) relatively smaller palpebral lobes & smaller eyes



Confusing the situation further, at least one other granulose calymenid species appears to be present in the Cincinnatian.  It sometimes co-occurs with Gravicalymene abbreviata.



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