A subway excavation crew in Los Angeles may have just made the find of the decade while working below Crenshaw Boulevard. They appear to have found a bison bone fragment and a hip join from a sloth in a sandy clay layer a couple weeks ago, and they were identified just recently.

“Immediately work was stopped and the experts came in and they took a look and did their proper recovery,” Metro spokesman Jose Ubaldo told KPCC. An expert of the La Brea Tar Pits and Museum helped to identify the bones, which could be anywhere from 10,000 to 40,000 years old.

The bones will be put on display at the National History Museum in Exposition Park, not bad for a normal day’s work for those construction workers.

Los Angeles was quite a wild place 12,000 years ago, about the time frame these bones come from. Back then, sabre-tooth tigers roamed the area, and they often hunted bison and horses, according to a study from the University of California – Los Angeles published earlier this year.

“Saber-toothed cats that roamed Los Angeles 12,000 years ago had many injuries to their shoulders and backbones that likely occurred when they killed large herbivore prey such as bison and horses, UCLA biologists report in the journal Nature Ecology and Evolution,” the statement from the university reads.

“The difference in neck injuries between the two animals is dramatic,” said lead author Caitlin Brown, a UCLA doctoral student in ecology and evolutionary biology. “The dire wolves had many neck injuries clustered together that could have resulted from the wolves being dragged by thrashing prey, as we see in modern wolves. In contrast, the saber-toothed cat has almost no neck or head injury, which implies that they were avoiding damage to their precious teeth.”

The La Brea Tar Pits of Los Angeles have long been a source of archaeological fascination due to the incredibly well preserved fossils. These samples have provided a window tens of thousands of years into the past.

A statement published in May by the American Museum of Natural History noted that 180 fossil insects preserved in the tar pits of Los Angeles indicate that climate in what is now southern California has been relatively stable in about the last 50,000 years.

“Despite La Brea’s significance as one of North America’s premier Late Pleistocene fossil localities, there remain large gaps in our understanding of its ecological history,” said lead author Anna Holden, a graduate student at the American Museum of Natural History’s Richard Gilder Graduate School and a research associate at the La Brea Tar Pits and Museum. “Recent advances are now allowing us to reconstruct the region’s paleoenvironment by analyzing a vast and previously under-studied collection from the tar pits: insects.”

As the most recent report notes, sloths also used to live in the Los Angeles area. Giant ground sloths evolved down in South America about 35 million years ago, and migrated to North America about 8 million years ago. The Ice Age changed the climate so severely that they found areas like Los Angeles inhospitable and begin to die out in the area.