Bones tens, and hundreds, of thousands of years old are being unearthed in Carlsbad, Calif. on land where the construction of more than 600 new houses is planned and had been underway. 

Among the Ice Age animals that have reappeared during the dig were giant bison, ancient bison and Colombian mammoths, according to the San Diego Union Tribune. There were also the bones of ancient horses and turtles among the fossils carved out of the dig site near Route 87 in Carlsbad.

The fossils range in age from about 50,000 to about 200,000 years old, which means that last time they had flesh on them was during the Pleistocene Epoch or the "Ice Age." 

One of the most intact specimen, a bison fossil that includes a skull and part of its skeleton, will go on display at the San Diego Natural History Museum, according to Tom Deméré, the museum's curator of paleontology.

"These are big animals, much larger than modern plains bison," Deméré told the Tribune.

The average weight of an ancient bison was about 2,000 lbs and the typical weight of giant Ice Age bison was around 2,250 lbs. Those Colombian mammoths, they weighed between 8 and 10 tons -- that's between 16,000 and 20,000 lbs.

The fossils were discovered back in July, as developer Cornerstone Communities of San Diego commissioned the grading of the future site of a development in Carlsbad's Quarry Creek area. The project, which could output up to 636 condos and other homes, has only been temporarily put on ice as paleontologist work the dirt.  

The community's pilot neighborhood is on track to be completed by the end of next year, but John Suster, the project's superintendent, said he told the paleontologists to take their time.

For Deméré, the dig is an exciting for the fields of paleontology and geology.

"The fossils have the potential to tell us a great deal about the climate, the environment, (and) the ecology of that time when they were living," Deméré said. "They are direct connections with the past, an ancient ecosystem that was once common here. We can understand how climates can change by studying these ancient ecosystems."

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