Unprecedented conservation of fossil feces from La Brea quarries

An example of coprolites from Rancho La Brea (A) before removing asphalt with surrounding sediments, (B) showing intact granules with plant material, (C) isolated, cleaned granules. Figure 2, from: Mychajliw et al. 2020. Exceptionally preserved asphalt coprolites expand the spatiotemporal range of the paleoecological representative of North America. Credit: Carrie Howard

While La Brea Ranch, commonly known as Tar Yama La Brea, is known for its thousands of bones of large extinct mammals, thanks to new excavation and chemical methods, great knowledge comes from small fossils.

Today, a team of researchers from La Brea Tar quarries, the University of Oklahoma, and the University of California at Irvine are reporting the first coprolites — or fossilized excrement — ever discovered in an asphalt or tar pit. These hundreds of fossilized rodent pellets were found during excavations in the garage for the Los Angeles County Museum of Art in Hancock Park in 2016, where more traditional La Brea fossils, such as extinct mammoths, scary wolves and sabers, were also found. Toothy cats.

Alexis Mikhailu, OU Researcher, is the lead author of the study. Details of the findings of the research team were published today in Scientific reports,

“It's unbelievable that after more than a century of excavation and research, we are still digging out new types of fossils from the treasury of La Brea deposits,” said Emily Lindsey, assistant curator at La Brea Tar Pits. "These tiny finds can lead to great discoveries about the climate and ecosystems of the Los Angeles ice age."

Initially, researchers were skeptical that there were many rats in the area.

“Previously, we noted random rodent fecal balls in the treated matrix, but this was easily explained as modern pollution,” said Laura Tewkesbury, senior trainer at La Brea Tar Pits.

But, when more and more pellets appeared on the asphalt, Tewkesbury recalled: “We silently looked at a huge number of pellets for a minute, and then looked at each other and said:“ There is simply no pollution. ”

Indeed, radiocarbon dates Generated in California, Irwin would confirm that the pellets were ~ 50,000 years old.

The La Brea Ranch is associated with the image of large animals stuck in “tar pits” or small, sticky asphalt puddles, where predatory animals are massively attracted to the fight against herbivorous prey. But these coprolites tell a new story about how to save the fossils in the La Brea Ranch.

“The intact nature and density of the fossils require a taphonomic explanation other than fishing. Conservation is a more likely result of asphalt leakage by an existing rodent nest“, said Karin Rice, a lead at La Brea Tar Pit.

Using a suite of advanced tools, including stable isotope analysis and scanning electron microscopyResearchers have shown that fecal pellets have been associated with perfectly preserved twigs, leaves, and seeds, apparently as part of an intact nest made by woodrow. Woodruds, also known as pacrates, are well known in the paleontological community for their accumulative behavior, which produces massive nests that can last for thousands of years. Pieces of plant material from these nests, in turn, are pictures of vegetation and climatic conditions of the past.

“This nest provides an unprecedented view of what was under the feet of the famous megafauna of the La Brea Ranch,” he said. “And for me, this emphasizes the importance of studying small mammals. Woodruds have survived the ice age and are still building nests in local urban green spaces such as Griffith Park! Studying these nests, we get a straight line from the past to the present with the help of which we can trace the human influence on the nature of Los Angeles over time. "

Scientists resume digging at LA Brea quarries in Los Angeles

Additional Information:
Mychajliw, A.M., Rice, K.A., Tewksbury, L.R. other. Exceptionally preserved asphalt coprolites expand the spatiotemporal range of the paleoecological representative of North America. Scientific representative 10, 5069 (2020). doi.org/10.1038/s41598-020-61996-y

Unprecedented conservation of fossil feces from La Brea quarries (March 20, 2020)
retrieved March 20, 2020
from https://phys.org/news/2020-03-unprecedented-fossil-feces-la-brea.html

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