These thin sandstone slabs are from the Permian Cloud Chief Formation from NW Oklahoma. They were collected from downstream of Lake Vincent in southern Ellis County.The bulk of the formation is composed of siltstone and claystone redbeds.
(Click to enlarge images) Pictured are the tops of the individual beds. The 1 cm bars are accurate, to show scale.
A few months after dropping some specimens off with the Oklahoma Geological Survey, they told me that there were probably "arthropod locomotion marks". Being busy with life in general, I accepted the answer without trying to determine "what sort of arthropods".
Recently, while looking at some of the slabs, I revisited a point of previous curiosity. Each trackway seemed to not have a companion for the opposite side of the critter. Perhaps because the critter was wider than the slab of rock.
So I started doing an internet search of Permian arthropods. An early result gave the word "Arthropleurid" as a likely suspect. An Arthropleurid was a large, centipede-like critter, in some cases up to 6 feet long. A later result gave this article, concerning the Late Pennsylvanian Cutler Group, in northcentral New Mexico.
If I get a chance to revisit the area, I will be looking for wider slabs, to hopefully find more-complete trackways and to document the occurrence a little better. Would like to maybe do a short paper/talk, maybe for a future GSA regional meeting. Or if I don't, maybe I will have somehow inspired someone else (in Oklahoma) to do so.
[The comments were generated with the original 2007 post.]
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