Very Large Dalmanites - 3.2 inches

This is a very large example of the classic New York trilobite Dalmanites limulurus. They average right around 2 inches, and ones over 3 are pretty hard to come by, this one is right at 3.2 inches. It's also in great shape, with beautiful shell detail and is laid out well. There is a few repaired cracks but no significant restoration. There are also a number of other fossil visible on the natural shale matrix on which it resides. A very aesthetic specimen all around.

Dalmanites is a very visually striking trilobite is one of the classic North American fossils. The distinctive compound eye, believed to be a stereoscopic motion detector, had lenses made of rigid crystal. Its armor, spikes, and visual acuity imply that Dalmanites was trying to keep itself off the menu.

The genus Dalmanites thrived across the globe in a variety of sea conditions and climate. It scanned the Ordivician (488-443 mya) and Silurian (444-415 mya) seas with the good depth perception of the shizochroal eye. Bony and jawed fish emerged in the Silurian, forcing trilobites to adapt or die in a greenhouse world of growing reefs and diverse predators.

The unique shizochroal adaptation of the suborder Phacopina is characterized by up to 700 relatively large, thick lenses made of the purest calcite. A doublet system of mounted lenses within the eye reduced distortion, while perched eyes promoted a wide field of view.

Caleb’s Quarry, in the Rochester Shale, is the primary source of richly detailed and well-preserved Dalmanites limulurus, as well as over 200 other species that tell the ecologic story of the Early Silurian. The famous shale is made from the relic Appalachian Mountains that were uplifted and eroded away into the shallow but deepening, warm seas of the Atlantic.

While the rocks around Lockport, NY have been worked for trilobites since the 1830's, the opening of Caleb's quarry in 1991 has significantly added to the quantity and quality of the material available. Working this quarry which spends much of the year under water is unquestionably difficult. Many hours of detailed preparation is required under microscope to extract and repair the trilobites which are found there.
Dalmanites limulurus
Middleport, New York
Rochester Shale
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