Prehistoric Fossilized Footprints Show Earliest Known Evidence of Mammals at the Seashore

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Coryphodon Reconstruction

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A restoration of the brown-bear-sized mammals (Coryphodon) that made countless tracks in a 58-million-year-old, brackish water lagoon in what is now southern Wyoming. Credit: Anton Wroblewski

Today, the rocks of the Hanna Formation in south-central Wyoming are numerous miles far from the closest ocean. But around 58 million years earlier, Wyoming was oceanfront residential or commercial property, with big hippo-like mammals traipsing through nearshore lagoons.

In a research study released in Scientific Reports, geologist Anton Wroblewski, an accessory associate teacher in the Department of Geology and Geophysics, and used biodiversity researcher Bonnie Gulas-Wroblewski of the Texas A&M Natural Resources Institute, report the discovery of numerous sets of fossilized tracks, likely from the brown bear-sized Coryphodon, that represent the earliest recognized proof of mammals collecting near an ocean.

“Trace fossils like footprints record interactions between organisms and their environments, providing information that body fossils alone cannot,” Wroblewski states. “In this case, trace fossils show that large- bodied mammals were regularly using marine environments only eight million years after non-avian dinosaurs went extinct.”

Anton Wroblewski Points to Mammal Track Underprints

Anton Wroblewski indicate an underprint made 58 million years earlier by a heavy mammal (most likely Coryphodon) strolling on the deltaic deposits above. Underprints kind when sediment is displaced downward by steps from heavy animals.” Credit: Anton Wroblewski

The tracks that the Drs. Wroblewski discovered in the Hanna Formation of Wyoming consist of underprints, impressions in soft sediment made when heavy animals stroll on overlying sediment layers, in addition to prints pushed into the surface areas of ancient tidal flats. Now protected in sandstone, the tracks are over half a mile (one kilometer) long and were made by 2 various animals, one with 4 toes and one with 5. The five-toed tracks follow Coryphodon, a semi-aquatic mammal comparable to a hippopotamus. The owner of the four-toed tracks stays a secret.

Mammal Tracks From Paleocene Lagoon

Section of the 58-million-year-old tracksite showing near-vertical tilting of the initially horizontal bed linen with 3 different trackways made by five-toed mammals strolling in parallel. Credit: Anton Wroblewski

“Paleontologists have been working in this area for thirty years, but they’ve been looking for bones, leaf fossils, and pollen, so they didn’t notice footprints or trackways,” Wroblewski states. He very first saw the tracks in September 2019. “When I found them, it was late afternoon and the setting sun hit them at just the right angle to make them visible on the tilted slabs of sandstone. At first, I couldn’t believe what I was seeing; I had walked by this outcrop for years without noticing them. Once I saw the first few, I followed out the ridge of sandstone and realized they were part of a much larger, more extensive trackway.”

Fossilized plants and pollen assisted the scientists identify the age of the tracks to be around 58 million years of ages, throughout the Paleocene date. Before this finding, the earliest recognized proof of mammals connecting with marine environments originated from the Eocene date, around 9.4 million years later on. Wroblewski states that the Hanna Formation tracks are the very first Paleocene mammal tracks discovered in the U.S.A. and just the 4th worldwide, with 2 sets of tracks formerly discovered in Canada and one in Svalbard, Norway. It’s likewise the biggest build-up of Paleocene mammal tracks worldwide in both aerial degree and the outright variety of tracks, he states. With a minimum of 2 types leaving the tracks, it’s likewise the most taxonomically varied.

Today’s big mammals gather near marine environments for a range of factors, consisting of security from predators and biting pests, foraging for special foods, and access to salt sources, which might have been restricted in the tropical forests of North America throughout the Paleocene. The scientists state ancient mammals might have had comparable factors for looking for a day at the beach.

The research study reveals, Wroblewski states, that hypotheses of habits and development based upon isotopic, molecular and body fossil information can be empirically checked utilizing trace fossils. “No other line of evidence directly records behaviors of extinct organisms preserved in their preferred habitats,” he states. “There’s still a lot of important information out there in the rocks, waiting for somebody to spot it when the lighting is just right!”

Reference: 13 May 2021, Scientific Reports.
DOI: 10.1038/s41598-021-88412-3