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Crinoid

Protaxocrinus aff. P. sideros

• Silurian
• Cybele Member, Jupiter Formation
• Anticosti Island, Quebec, Canada

Size: ~3 cm across the arms

This specimen is mostly consistent with the description of Protaxocrinus sideros (Ausich & Copper 2010), but with a few oddities. The arms' brachials are incredibly wide, easily 3-4 times wider than high for the primibrachials and secundibrachials, as opposed to being around twice as wide (Ausich & Copper 2010). In fact, the first primibrachials are significantly larger and wider than even the radials, and laterally-abutting each other from adjacent rays. Moreover, the proximal brachials are hexagonal in shape and laterally-pointed, as opposed to being rectangular with smooth lateral surfaces (Ausich & Copper 2010).

William Ausich believes this specimen may fit withinin the range of P. sideros morphology. He has also pointed out evidence of non-lethal predation followed by regeneration in some of the very thin distal arms.

Also note the very strong coiling of one of the distal arm branches, which is a rarely-seen feature due to the incurving nature of typical flexible crinoid arms.

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