Protonympha
P. transversa from Conway Morris and Grazhdankin 2006
Species: P. salicifolia (type), P. transversa (referred)
Etymology:
Age and Location: Devonian of New York
Classification: incertae sedis
We have no idea what this one is. It’s some kind of bilaterally symmetric, frond-like, segmented...thing. It seems to have been leathery and sac-like. Beyond that, it’s a total mystery. It doesn’t have an obvious back, front, top, or bottom. Between its totally enigmatic nature and its preservation as a sandstone impression, it resembles an Ediacaran fossil, despite being a quarter billion years more recent. While similarities have been proposed to polychaete worms, the arm of a starfish, a fish’s egg case, arthropods, and other things, no explanation seems to be satisfactory.
Sources:
Conway Morris S., Grazhdankin D. 2005. Enigmatic worm-like organisms from the Upper Devonian of New York: An apparent example of Ediacaran-like preservation. Palaeontology 48:395–410.
Morris S., Grazhdankin D. 2006. A post-script to the enigmatic Protonympha (Devonian; New York): Is it an arm of the echinoderms? Palaeontology 49:1335–1338.