I very recently found what I believe to be two starfish fossils from the Wann Formation (Late Pennsylvanian age) in Oklahoma. At the locality I found these, the Wann is a bioturbated sandstone and shale formation, preserving several flute casts and burrows, and some plant debris. Interestingly, these starfish are preserved in sandstone and the paleocurrent is also preserved (lower left to upper right, following the striations in the upper specimen, and is also indicated by the orientation and slight splay of the starfish arms in the upper specimen). Below the Wann are the Iola and Chanute Formations, both of which are fossiliferous carbonate formations containing several mollusks and bryozoa. The third starfish in the above photo is a modern starfish included for reference.
I can’t help but think that these starfish must have been buried very rapidly, very near the shoreline, and were subject to wave action. As each wave receded, sediment was dragged from the shoreline into deeper water, piling up along the shoreward side of each starfish, and quickly buried them. Perhaps their demise was caused by a storm event, such as a hurricane or tropical storm, causing increased wave activity, or river flooding, causing increased sediment discharge. Or perhaps a little of both: flooding caused by a marine storm. If anyone has any thoughts, I’d love to hear them.
Update 10/25/19: Perhaps they’re peculiar looking burrows instead?