New trace fossil discoveries from the half-billion-year-old Cambrian tidal flats of Wisconsin at a site called Blackberry Hill continue to paint the picture of some of the earliest animals to set foot on land and what they might have been eating.
The mollusk trail Climactichnites blackberriensis (Cb) presumably stopping to eat a scyphozoan (jellyfish) that had washed up on shore. CS = clasts of a scyphozoan; DS = decomposing scyphozoan; R = ripple marks; S = scyphozoan.
Trace and body fossils from Blackberry Hill had already revealed the identity of the animal (a millipede-relative called a euthycarcinoid) that produced the trackway Protichnites, which literally means ‘first footprints.’
The identity of that animal had mystified paleontologists for over 150 years.
Also found on these tidal flats were body fossils of a crustacean known as a phyllocarid and thousands of well-preserved trace fossils produced by various arthropods and mollusks.
One of the new traces, Climactichnites blackberriensis, is a large trail that was probably produced by an unidentified mollusk.
The animal made the trail as it advanced forward on the tidal flat.
Significantly, as the animal traveled, it appears to have stopped to feed on a scyphozoan (jellyfish) that had stranded onshore.
Cochlichnus? – the presumed resting trace of a polychaete worm.
Chunks of material (clasts) litter the area, and scyphozoans are seen in the vicinity.
If interpreted correctly, this would be the first fossil evidence of an animal feeding on a scyphozoan on a Cambrian tidal flat.
Also, this may have been an incentive for certain animals to come ashore and begin the terrestrialization process.
Other new trace fossils include a resting trace of a possible polychaete worm, including impressions of its parapodia (limbs), and the oldest occurrence of Stiallia pilosa (a likely feeding trace of an arthropod, such as a euthycarcinoid).
Stiallia – the presumed feeding trace of an arthropod.
Researchers Kenneth C. Gass (Milwaukee Public Museum) and Nora Noffke (Old Dominion University) recently published their findings in the Journal of Paleontology.
The authors also presented evidence suggesting that some trackways may have been produced by a certain species of extinct primitive arthropod called an aglaspidid, whose spike-like tail was bifurcated near its end.
“This shows that Cambrian tidal flats were busier than we had thought. It almost seems as though all of these animals were gathering at the tidal flats just itching to make a break for land,” said Gass.
“More taxonomic and behavioral diversity at these tidal flats is sure to come to light with further field work and material analysis.”
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K. Gass & N. Noffke. 2026. New ichnotaxa from the tidal flat facies of the Cambrian Elk Mound Group, Wisconsin, USA. Journal of Paleontology, p. 1-15; doi: 10.1017/jpa.2026.10225
