Rare Reptile Bones, Millions of Years Old Excavated in North Park

Six inches below loose soil, amidst a sea of sagebrush, four paleontologists work meticulously with brushes, picks, and other tools, to uncover 50 to 60-million-year-old crocodile and turtle bones.

It’s a windy and cold day in North Park, Colorado. Snow-capped mountains rise from the horizon amid clouds sprinkled across the blue sky. The soft, dry soil absorbs my footprints as I approach the fossil excavation site on Bureau of Land Management (BLM) managed public land in the Coalmont Formation.

Named for deposits found near Coalmont, Colorado and along the North Platte River, fossil leaves and pollen date the formation to the late Paleocene and early Eocene Epochs, approximately 50 to 60-million years old.

Millions of years ago, the environment in North Park was different from the dry, sagebrush-covered landscape of present. The climate was tropical, and the animals and plants inhabited shallow ponds and swamps at a time when volcanic eruptions in what is now Colorado were common occurrences. Plant and fish fossils have been previously discovered in the Coalmont Formation, but this is the first discovery of reptile bones, and a cause for much paleontological excitement.

“We are excited the BLM approved our collection permit to collect the first known crocodile discovered in the Coalmont Formation,” says Geraldine Aron, paleontologist and President of Paleo Solutions, Inc., the company excavating the rare fossils.

At first glance, the one square meter excavation area looks like a pile of dirt. Closer examination reveals a vertebra, teeth, bits of turtle shell, and various limb bones. The paleontologists identify the bones as crocodile due to the presence of osteoderms - bony scales identical to those of modern crocodiles. A few paces away from the main excavation site, a rib bone lies uncovered. Paleontologists think it belongs to a turtle, but more research is needed to confirm.

“Paleontological resources provide a glimpse into past environments and time periods. This new fossil discovery is scientifically important because it adds crocodiles and turtles to the list of fossils known in this formation,” says Dr. Paul C. Murphey, Vice President and Principal Paleontologist of Paleo Solutions, Inc. “This site is so rich that future collection efforts may even produce a fossil mammal, and just one mammal tooth would be extremely useful for more precisely dating all of the fossils found here.”

The fossils were discovered in the summer of 2017 during a 3D geophysical investigation to locate oil in the North Park Basin. Prior to any surface-disturbing activity on BLM-managed public land, a cultural resource survey is required in compliance with the National Historic Preservation Act. A paleontological resource survey may be required under BLM policy, depending on the potential for paleontological resources in the area. BLM works to protect and preserve the cultural and paleontological resources found on the 8.3 million acres of public land BLM manages in Colorado.

Due to the rarity of the fossils, the paleontologists with Paleo Solutions are excavating and sending the fossils to the Denver Museum of Nature and Science for preservation and research. The paleontologists are excavating the fossils as a block. They will not fully know what the block contains until it is transported to the museum's lab.

Over the two-day excavation, the fossils are prepared for transport. Paleontologists trench the entire specimen, removing earth around the edge of the fossil area to form a mushroom shape. Then the fossils undergo the jacketing process – constructing a plaster bandage to prevent damage during transport. The mushroom top is covered with a plaster and burlap casing. Once dry, the plaster jackets are separated from the soil base and ready for transport.

Excavation is tedious work, but the paleontologists love it. During our time at the site, they uncover a tooth and some ancient fish poop. I stare at the dime-sized, brown spot of fish poop in the dry chunk of soil, amazed at what you can find after millions of years under dirt.

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