Psilonichnus quietis isp. nov. from the Eocene Iwaki formation, Shiramizu group, Joban coal field, Japan

Abstract

Psilonichnus quietis isp. nov. is characterized as an unlined vertical‐to‐inclined burrow ranging in diameter from 0.4 to 2.8 cm, with four different shapes of swelling. It exhibits three intergradational architectural patterns, herein termed Type I, Type II and Type III. Psilonichnus quietis was produced by brachyuran crabs. Types I and Type II were constructed by adult crabs, but Type III by juveniles. Type I and Type III burrows were produced by continuous burrowing whereas Type II burrows were produced by intermittent burrowing. Psilonichnus quietis occurs in various host rocks ranging lithologically from mudstone to sandstone of the Eocene Iwaki Formation, Shiramizu Group, exposed at the Joban coal field, Japan.

Keywords:

• Psilonichnus quietis
• Eocene
• Iwaki Formation
• Joban coal field
• Japan

Notes

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